Process for preparing 3-deoxy-B-D-threo-pentofuranosyl nucleosides

FIELD OF THE INVENTION
The present invention relates to novel intermediates useful for synthesizing various dideoxynucleoside derivatives, synthetic processes thereof, and novel dideoxynucleoside derivatives which may be synthesized from these intermediates and may be used as effective antiviral agent.
PRIOR ART
Dideoxynucleosides have now been paid attention as an effective antiviral agent for AIDS virus (HTLV III) which is a kind of retrovirus. Effectiveness of azidothymidine, dideoxycytidine, dideoxyadenosine, etc. has hitherto been confirmed, and researches on other dideoxynucleoside derivatives are also proceeded with (Inhibition of the in vitro infectivity and cytopathic effect of human T-lymphotrophic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV) by 2',3'-dideoxynucleosides; and Hiroaki Mitsuya and Samuel Broder, Proc. Natl. Acad. Sci., USA vol. 83, pp. 1911-1915, March 1986, Medical Sciences).
2',3'-Dideoxyadenosine, 2',3'-dideoxyinosine, 2',3'-dideoxyguanosine and 2',3'-dideoxycytidine are sold by BIOCHEMICAL CO. in USA. These compounds are prepared using a conventional method for preparing 2',3'-dideoxycytidine (Horwitz et al., J. Org. Chem., 32(3), 817-818 (1967)) or a conventional method for preparing 2',3'-dideoxyguanosine (Prisbe et al., Synth. Commun. 1985, 15(5), 401-409).
European Patent Publication No. 206497A discloses the use of 2',3'-dideoxyinosine as an antiviral agent.
Further, the aforementioned article of Hiroaki Mitsuya et al., and Japanese Patent Unexamined Published Application No. 61-280500 disclose the use of various 2',3'-dideoxynucleosides and their derivatives as an antiviral agent, particularly against AIDS virus.
As for a synthetic method of nucleoside intermediates useful for synthesizing various dideoxynucleoside derivatives, there are prior researches by M. J. Robins, Nyilas, Chattopadhyaya, Reese, Sasaki and others. However, these synthetic methods are not fully satisfactory for industrial synthesis of dideoxynucleoside derivatives from the reason that steps required for the synthesis are long, complicated steps including an oxidation reaction follow, reagents not suitable for a large scale preparation are used, etc. Literatures with respect to these synthetic methods are enumerated below.
1) M. J. Robins et al., J. Org. Chem. 39, 2564 (1974).
2) F. Hansske and M. J. Robins, Tetrahedron Lett., 26, 4295 (1985).
3) F. Hansske, D. Madej, and M. J. Robins, Tetrahedron, 40, 125 (1984).
4) F. Hansske and M. J. Robins, J. A. Chem. Soc., 105, 6736 (1983).
5) A. Nyilas and J. Chattopadhyaya, Synthesis., 1986, 196.
6) H. Bazin and J. Chattopadhyaya, Synthesis, 1985, 1108.
7) D. G. Norman and C. B. Reese, Synthesis, 1983, 304.
8) T. Sasaki, K. Minamoto and S. Tanizawa, J. Org. Chem. 38, 2896 (1973).
Among dideoxynucleoside derivatives, one of which is now practically used as a AIDS therapeutic agent is azidothymidine. However, azidothymidine brings about strong side effects and has only an inadequate AIDS virus growth-inhibiting effect. Therefore, researches on various dideoxynucleoside derivatives must successively be proceeded with.
OBJECTS OF THE INVENTION
An object of the present invention is to provide novel dideoxynucleoside derivatives which are effective as antiviral agents.
Another object of the present invention is to provide novel nucleoside derivatives which are usable as intermediates useful for synthesis of various dideoxynucleoside derivatives.
Further object of the present invention is to provide simple synthetic methods suitable for a large scale synthesis of the above intermediates.
DESCRIPTION OF THE INVENTION
The present invention relates to nucleoside derivatives represented by the following general formula I: ##STR3## wherein B is a purine base residue optionally having a protective group, a pyrimidine base residue optionally having a protectivie group or a imidazolyl group optionally having a protective group; R.sup.1 and R.sup.3 are a PivO-group, a TsO-group, a DMTrO-group or a benzoyl group; R.sup.2 is a MsO-group, a TflO-group or a TsO-group.
Further, the present invention relates to nucleoside derivatives represented by the following general formula II: ##STR4## wherein B is a purine base residue optionally having a protective group, a pyrimidine base residue optionally having a protective group or a imidazolyl group optionally having a protective group; R.sup.1 is OR.sup.4 wherein R.sup.4 is a protective group or a hydrogen atom; R.sup.3 is a TsO-group, a MsO-group, a TflO-group, a PivO-group, a benzoyl group, a hydroxyl group, a mercapto group, an alkylmercapto group, an arylmercapto group, an azido group, an isothiocyanato group, a halogen atom or a hydrogen atom; R.sub.3 ' is a MsO-group, a TsO-group, ##STR5## a hydroxyl group or hydrogen atom; provided that only one of R.sup.3 and R.sup.3' is always a hydrogen atom; and when B is a cytosine residue having no protective group, at least one of R.sup.1 and R.sup.3' is other than a hydroxyl group and R.sup.3 is not an azido group; further, when B is an adenine residue having no protective group, at least one of R.sup.1 and R.sup.3' is other than a hydroxyl group.
Further the present invention relates to a process for synthesizing a nucleoside derivative represented by the formula [II']: ##STR6## (wherein B is a purine base residue optionally having a protective group, a pyrimidine base residue optionally having a protective group or an imidazolyl group optionally having a protective group; R.sub.1 is OR.sup.4 wherein R.sup.4 is a protective group or a hydroxyl group; R.sup.3 is a hydrogen atom; and R.sup.3' is a hydroxyl group), which comprises treating a compound represented by the formula [I']: ##STR7## (wherein B is a purine base residue optinally having a protective group, a pyrimidine base residue optionally having a protective group or an imidazolyl group optionally having a protective group; R.sup.1 and R.sup.3 are a PiVO-group, a TsO-group, a DMTrO-group, a benzoyl group or a hydroxyl group; and R.sup.2 is a MsO-group, a TflO-group or a TsO-group) with a base and a reducing agent.
Further the present invention relates to the process for selectively eliminating the Piv-group of B alone in the nucleoside derivatives represented by the formula [I"]; ##STR8## (wherein B is a purine base residue protected by a Piv-group, a pyrimidine base residue protected by a Piv-group or an imidazolyl group protected by a Piv-group; R.sup.1 and R.sup.3 are a PivO-group; R.sup.2 is a MsO-group, TflO-group, TsO-group, hydroxyl group or a hydrogen atom), which comprises treating nucleoside derivatives [I"] with an alkaline compound.
The present invention is explained in more detail below.
Base B in the nucleoside derivatives [I] and [II] of the present invention usually binds to the 1'-position of the ribose through a nitrogen atom in the base B, but may bind to the 1'-position of the ribose through a carbon atom therein.
In the present specification, Ms- means a mesyl group (CH.sub.3 SO.sub.2 --), Ts- means a tosyl group ##STR9## Tfl- means a trifluoromethanesulfonyl group (CF.sub.3 SO.sub.2 --), Piv- means a pivaloyl group [(CH.sub.3).sub.3 CO--] and DMTr- means a 4,4'-dimethoxytrityl group.
Further, the purine base means purine derivatives having close relation to a living body. These purine derivatives are included in nucleic acids: adenines and guanines in coenzymes; uric acid, hypoxanthine, xanthine, and the like which have close relation to purine metabolism of a living body; caffeine, theophylline, theobromine and the like which are called purine alkaloids; isoguanine in a nucleoside called crotonoside; methylaminopurine synthesized when a living body is placed under a special condition; etc.
The following compounds are specifically exemplified as purine bases:
Adenine, 1-methyladenine, 2-methyladenine, N-(purine-6-yl-carbamoyl)-L-threonine, N.sup.6 -(.DELTA..sup.2 -isopentenyl)adenine, 2-methylthio-N.sup.6 -(.DELTA..sup.2 -isopentenyl)adenine, 2-hydroxyadenine, N.sup.6 -methyladenine, N.sup.6,N.sup.6 -dimethyladenine, N.sup.6 -(cis-4-hydroxyisopentenyl)adenine, N.sup.6 -(trans-4-hydroxyisopentenyl) adenine, 2-aminoadenine, guanine, 1-methylguanine, N.sup.2 -methylguanine, N.sup.2,N.sup.2 -dimethylguanine, 7-methylguanine, wye, wybutine, peroxywybutine, hypoxanthine, 1-methylhypoxanthine, xanthine, uric acid, 6-thiopurine, 6-chloropurine, 2,6-diaminopurine, etc.
Further, the pyrimidine base means pyrimidine derivatives having close relation to a living body. The following compounds are exemplified as main pyrimidine bases:
______________________________________cytosine 4-amino-2-oxypyrimidineuracil 2,4-dioxypyrimidinethymine 2,4-dioxy-5-methylpyrimidine5-methylcytosine 4-amino-2-oxy-5-methylpyrimidineoxymethylcytosine 4-amino-2-oxy-5-oxymethylpyrimidine______________________________________
The following compounds are specifically exemplified as other pyrimidine bases:
3-methylcytosine, N.sup.4 -acetylcytosine, N.sup.4 -methylcytosine, 2-thiocytosine, 3-methyluracil, 4-thiouracil, 5-hydroxyuracil, 5-hydroxymethyluracil, 5-methoxyuracil, 5-carboxymethyluracil, 2-thiothymine, 5-carboxymethyl-2-thiouracil, 5-(methoxycarbonylmethyl)-2-thiouracil, 5-(N-methylaminomethyl)-2-thiouracil, 5,6-dihydrouracil, 5,6-dihydrothymine, 5-(putrescinomethyl)uracil, S(+) 5-(4,5-dihydroxypentyl)uracil, 6-carboxyuracil, 5-fluorouracil, 5-iodouracil, etc.
Examples of the protective group contained in base B and the protective group of the oxygen atom of the R.sub.1 may include a trityl group, a monomethoxytrityl group, a dimethoxytrityl group, a silicon derivative group, a pivaloyl group, an alkyl group, an acyl group, etc.
An example of nucleoside derivatives and synthetic methods thereof of the present invention is shown in schemes 1 and 2, and various embodiments of the present invention is described together therewith. ##STR10##
NOVEL COMPOUNDS
Specific examples of nucleoside derivatives represented by the general formula [I] of the present invention are shown in Table 1.
TABLE 1______________________________________ ProtectiveCom- grouppounds B of B R.sup.1 R.sup.2 R.sup.3______________________________________A3 adenine DMTr-- DMTrO-- MsO-- TsO-- residueC3 cytosine Piv-- PivO-- " PivO-- residueC5 " none " " "C6 " DMTr-- " " "U2 uracil none " " " residueG2 guanine Piv-- " " " residueA'2 adenine " " " " residue______________________________________
Specific examples of nucleoside derivatives represented by the general formula [II] of the present invention are shown in Table 2.
TABLE 2__________________________________________________________________________ ProtectiveCompounds B group of B R.sup.1 R.sup.3 R.sup.3'__________________________________________________________________________A6 adenine residue DMTr DMTrO H HOA7a " " " " MsOA7b " " " " TsOA8 " " " N.sub.3 HA9 " none HO " "A10 " DMTr DMTrO I "C7 cytosine residue DMTr HO H HOC8a " " DMTrO " "C8b " Piv PivO " "C9a " DMTr DMTrO " MsOC9b " " " " TsOC9c " Piv PivO " TsOC9d " " " " ##STR11##C9e " " " " ##STR12##U3 uracil residue none HO " HOG3 guanine residue " " " "A'3 adenine residue " " " "__________________________________________________________________________
(The reaction of [I'].fwdarw.[II'])
The reaction for synthesizing nucleoside derivatives represented by the general formula [II'] from those represented by the general formula [I'] (hereinafter referred to as [I'].fwdarw.[II'] reaction) is to provide nucleoside derivatives, wherein an amino group of the base residue and hydroxy groups at 2'- and 5'-positions of the ribose residue are protected and a mesyl group, a tosyl group or a trifluoromethanesulfonyl group is selectively introduced into 3'-position of the ribose residue. The resulting nucleoside derivatives are treated with a base and a reducing agent so as to effectively synthesize intermediates useful for the synthesis of dideoxynucleoside derivatives.
A mesyl group is most preferable as a functional group which is to be selectively introduced into the 3'-position of the ribose and the reaction rate thereof is very high. In order to introduce the above mentioned functional group into the 3'-position of the ribose, first of all the nucleoside is treated in a conventional manner so as to introduce selectively a protective group such as pivaloyl group into the base residue (the 2'- and 5'-positions of the ribose), then the above mentioned functional group is introduced into the 3'-position of the ribose. Thus the synthetic methods of this invention of the [I'].fwdarw.[II'] reaction is carried out by employing the novel nucleoside derivatives as an intermediate which is prepared by introducing the above mentioned functional group into the 3'-position of the ribose. The [I'].fwdarw.[II'] reaction may be carried out without isolating the compound of [I'] by continuously carrying out the processes of introducing the protective group such as pivaloyl group into the nucleoside and introducing the above mentioned functional group.
Reaction examples of the [I'].fwdarw.[II'] reaction and reaction conditions under which the reaction is carried out are as follows:
______________________________________Reaction examples______________________________________Compound A3 .fwdarw. A6Compound A5 .fwdarw. A6Compound C3 .fwdarw. C4aCompound C6 .fwdarw. C7Compound U2 .fwdarw. U3Compound G2 .fwdarw. G3Compound A'2 .fwdarw. A'3______________________________________
ii) Reaction conditions
a) Solvent
It is preferable to use a mixed solvent containing an alcohol as the solvent, and for example, methanol, ethanol, propanol, water, benzene, toluene, hexane, chloroform, dichloroethane, N,N-dimethylformamide, dimethylsulfoxide, ether, tetrahydrofuran, dioxane, ethyl acetate, acetonitrile, etc. may be used. Further, heavy water (D.sub.2 O, T.sub.2 O), or a heavy hydrogen- of tritium-labelled alcohol may be used.
b) Reagents
As reagents, a metal alkoxide or another alkaline substance as the base, and a reducing agent may be used in an amount of 1 to 20 mole equivalents, respectively.
Preferred metal alkoxides include alkoxides such as methoxide, ethoxide, propoxide and t-butoxide of an alkali metal, an alkaline earth metal, etc., particularly magnesium, lithium, potassium, sodium or the like. Magnesium methoxide, sodium methoxide and potassium hydroxide may most advantageously be used.
Other preferable alkaline substances include sodium hydroxide, an alkylalium compound, an alkyl lithium compound, etc.
Preferred reducing agents include a metal borohydride complex containing an alkali metal or alkaline earth metal represented by sodium borohydride (NaBH.sub.4), sodium cyanoborohydride, lithium cyanoborohydride, tetraalkylammonium borohydride, diborane, an aluminum-hydrogen complex represented by lithium aluminum hydride (LiAlH.sub.4), an organotin hydride represented by tributyltin hydride. Further, these compounds may be those heavy hydrogen- or tritium-labelled.
c) Other conditions
Reaction time is preferably 5 minutes to 20 hours, and reaction temperature is 0.degree. to 100.degree. C. Further, it is preferable to carry out the reaction in an inert gas such as nitrogen.
(The reaction of selectively eliminating the Piv-group alone in the compound [I"])
Reaction examples of the reaction for selectively eliminating the Piv-group of B alone in the nucleoside derivatives represented by the formula [I"] and reaction conditions under which the reaction is carried out are as follows:
Reaction example C3.fwdarw.C5
ii) Reaction conditions
a) Solvent
Water, methanol, ethanol, benzene, toluene, hexane, ethyl acetate, tetrahydrofuran, chloroform, ether, etc. may be used as the solvent.
b) Reagent
An alkaline compound such as a magnesium alkoxide, sodium hydroxide or potassium hydroxide is generally be used as the reagent. A magnesium alkoxide is the most preferable. When other alkaline compounds are used, temperature condition and reaction time must be controlled so that the pivaloyl group of the base alone is eliminated.
c) Other reaction conditions
Reaction time is 5 to 20 hours, and reaction temperature is 0.degree. to 100.degree. C.
(Reactions in each step shown in schemes)
Preferable and acceptable reaction conditions under which each of the reaction steps exemplified in schemes 1-5 is carried out are mentioned below.
Various protective groups such as trityl groups, monomethoxytrityl groups, dimethoxytrityl groups, silicon derivative groups, alkyl groups, pivaloyl groups and acyl groups may be used for the hydroxyl group at the 5'-position of ribose and the amino group of the base in each step shown in scheme 1. However, the protective groups may be present or absent except that it is required to protect the hydroxyl group at the 5'-position of the ribose in the mesylation and tosylation steps. Further, it is preferable in order to increase solubility of the nucleoside derivatives in organic solvents that either the hydroxyl group at the 5'-position of the ribose or the amino group of the base is protected.
As for synthetic methods of Compound C2 shown in scheme 2, it makes reference to Kazuo Kamaike, Fumihiko Uemura, S. Yamakage, S. Nishino, and Shunichi Ishido, "Simple synthetic procedure for 2'- and -3'-tetrahydropyranyl ribonucleoside derivatives involving regioselective acylation with acyl chlorides, and synthesis of ribonucleotide oligomers" Nucleic Acid Research, Symposium Series No. 16, 1985; Nucleosides & Nucleotides, 6, 699 (1987).
In order to synthesize Compound C3 with protection of Compound C1, it is preferable to protect the amino group of the base and the ribose 5'- and 2'-positions at the same time using pivaloyl groups as shown in scheme 2. However, acetyl groups and benzoyl groups may each also be used in place of pivaloyl groups under an adjusted reaction condition. Further, it is also possible to synthesize Compound C8a from Compound C1 through a route shown in scheme 6. ##STR13##
It is difficult to apply the (A3 A6)-type reaction (scheme 1) using the 2'-tosylated compound to the steps for synthesizing C4a and C7 (scheme 2) because of the existence of the carbonyl group in the base. When the base does not have the carbonyl group which participates in the 2'-position or the carbonyl group of the base is protected, the 2'-tosylated compounds may be used. A method where the keto group of the base is opened and the oxygen is methylated to make an enol type may, for example, be utilized for protecting the carbonyl group of the base.
Compound C4a [1-(3-deoxy-.beta.-D-threo-pentofuranosyl) cytosine] and biological properties thereof are disclosed in the report by W. Kreis, K. A. Watanabe, and J. J. Fox [Helv. Chem. Acta, 61, 1011 (1978)].
Compound C11 (2'-azido-2',3'-dideoxycytidine) and biological properties thereof are disclosed in the report by Shunji Izuta, Shigeru Kimura, Kenji Takenuki, and Mineo Saneyoshi, (Nucleic Acid Research, Simp. Ser., No. 17, 1986, p. 154).
1) Synthesis of Compounds A1 and A4
Compound A1 and Compound A4, starting compounds disclosed in scheme 1 may be obtained by a known method, for example by tosylating the nucleoside in the route shown in the following scheme 7. ##STR14##
The 2'-O-tosyl compound (Compound A1) and the 3'-O-tosyl compound (Compound A4) may readily be separated by fractional crystallization. Heretofore, a method of obtaining an intermediate (corresponding to Compound A6) for synthesis of dideoxynucleoside derivatives from the 3'-O-tosyl compound (Compound A4) has been known (F. Hansske and M. J. Robins, J. Am. Chem. Soc., 105, 6736 (1983)). However, in this method the large scale preparation of the 3'-O-tosyl compound (Compound A4) is tedious. On the other hand, synthetic method of the invention allows the use of the 2'-O-tosyl compound in addition to the 3'-O-tosyl compound as the starting materials.
Though the starting material used in scheme 7 is adenosine, such nucleosides as specifically exemplified below may further be used in the present invention in place of adenosine:
1-methyladenosine, 2-methyladenosine, N.sup.6 -methyladenosine, N.sup.6,N.sup.6 -dimethyladenosine, 2-hydroxyadenosine, N-[(9-.beta.-D-ribofuranosylpurin-6-yl)carbamoyl]-L-threonine, N-[(9-.beta.-D-riboranosyl(purin-6-yl)-N-methylcarbamoyl]threonine, N-[(9-.beta.-D-ribofranosyl-2-methylthiopurin-6-yl)carbamoyl]threonine, N.sup.6 -(.DELTA..sup.2 -isopentenyl)adenosine, 2-methylthio-N.sup.6 -(.DELTA..sup.2 -isopentenyl)adenosine, N.sup.6 -(cis-4-hydroxyisopentenyl)adenosine, 2-methylthio-N.sup.6 -(Cis-4-hydroxyisopentenyl)adenosine, zeatosine, cytidine, 2-thiocytidine, 3-methylcytidine, N.sup.4 -acetylcytidine, 5-methylcytidine, guanosine, 1-methylguanosine, N.sup.2 -methylguanosine, N.sup.2,N.sup.2 -dimethylguanosine, N.sup.2,N.sup.2 -dimethylguanosine, 7-methylguanosine, N.sup.2,N.sup.2,7-trimethylguanosine, wyosine, wybutosine, peroxywybutosine, Q nucleoside, Q*uncleoside (the compound where the hydroxyl hydrogen atom at the 5-position of the cyclopentene of Q uncleoside is replaced by a galactosyl residue depicted below). ##STR15## inosine, 1-methylinosine, xanthosine, uridine, 3-methyluridine, 5-methyluridine, 5-methyl-2-thiouridine, 4-thiouridine, 5-carboxymethyluridine, 5-carboxymethyl-2-thiouridine, 5-(carboxymethylaminomethyl)uridine, 5-(carboxymethylaminomethyl)-2-thioridine, 5-(methoxycabonylmethyl)uridine, 5-(methoxycarbonylmethyl)-2-thiouridine, 5-(methylaminomethyl)-2-thioridine, 3-(3-amino-3-carboxypropyl)uridine, 5-hydroxyuridine, 5-methoxyuridine, methyluridine-5-oxyacetate, 5-hydroxymethyluridine, dihydrouridine, 5-methyl-5,6-dihydrouridine, pseudouridine, 1-methyl-3-(3-amino-3-carboxypropyl)pseudouridine, orotidine, etc.
2) Compound A1.fwdarw.Compound A2
Compound A2 may be obtained by reacting Compound A1 with dimethoxytrityl chloride in a solvent such as pyridine or triethylamine, preferably at a temperature of 65.degree. to 85.degree. C. for 1 to 3 hours.
General reaction conditions for obtaining Compound A2 from Compound A1 are as follows.
a) Solvent
As the solvent, a solvent mainly consisting of pyridine or triethylamine is used. However, an aprotic organic solvent may be used in combination therewith. Examples of the aprotic organic solvent are benzene, toluene, hexane, chloroform, dichloroethane, dichloromethane, N',N-dimethylformamide, dimethylsulfoxide, ether, tetrahydrofuran, dioxane, ethyl acetate, acetonitrile, etc.
However, a neutral solvent is used when 3,4-dihydro-2H-pyran is used as a reagent.
b) Catalyst
As a catalyst, 4-dimethylaminopyridine, an alkali metal or alkaline earth metal alkoxide (sodium methoxide, etc.), one of various Grignard reagents (t-butylmagnesium chloride, etc.).or the like is used in an amount of 0.1 to 10 mole equivalents.
However, when the pyran is used as a reagent, benzenesulfonic acid, toluenesulfonic acid, camphorsulfonic acid, Hydrochloric acid, sulfuric acid, a strongly acidic ion exchange regin or the like is used as an acid catalyst.
c) Reagent
As a reagent, trityl chloride, monomethoxytrityl chloride, dimethoxytrityl chloride, benzyl chloride, benzyl bromide, monomethoxybenzyl chloride, monomethoxybenzyl bromide, dimethoxybenzyl chloride, dimethoxybenzyl chloride, .beta.-methoxyethoxymethyl chloride, methoxymethyl chloride, benzoyl chloride, acetyl chloride, pivaloyl chloride, t-butyldimethylsilyl chloride, dimethylphenylsilyl chloride, 3,4-dihydro-2H-pyran or the like is used.
d) Other conditions
Reaction time is 10 minutes to 20 hours, reaction temperature is 0.degree. to 100.degree. C., and the reaction is carried out at normal pressure while humidity is avoided.
3) Compound A2.fwdarw.Compound A3
Compound A3 may be obtained by reacting Compound A2 with mesyl chloride in a solvent such as pyridine or triethylamine, preferably at room temperature for 1 to 3 hours.
General reaction conditions for obtaining Compound A3 from Compound A2 are as follows.
a) Solvent
As the solvent, a solvent mainly consisting of pyridine or triethylamine is used. However, an aprotic organic solvent may be used in combination therewith. Examples of the aprotic organic solvent are benzene, toluene, hexane, chloroform, dichloroethane, dichloromethane, N,N-dimethylformamide, dimethylsulfoxide, ether, tetrahydrofuran, dioxane, ethyl acetate, acetonitrile, etc.
b) Catalyst
As a catalyst, 4-dimethylaminopyridine, an alkali metal or alkaline earth metal alkoxide (sodium methoxide, etc.), one of various Grignard reagents (t-butylmagnesium chloride, etc.) or the like is used in an amount of 0.1 to 10 mole equivalents.
c) Reagent
As the reagent, an acid chloride, acid anhydride, acid imidazolide or the like of methanesulfonic acid, toluenesulfonic acid, trifluoromethanesulfonic acid or the like may be used.
d) Other conditions
Reaction time is 10 minutes to 20 hours, reaction temperature is 0.degree. to 100.degree. C., and the reaction is carried out at normal pressure while humidity is avoid.
4) Compound A3.fwdarw.Compound A6
Compound A6 may be obtained by reacting Compound 3 with magnesium methoxide, sodium methoxide or the like in the presence of a reducing agent such as sodium borohydride in a benzene-methanol mixed solvent at a temperature of 55.degree. to 75.degree. C. for 3 to 7 hours.
General reaction conditions are the same with those of the [I'].fwdarw.[II'] reaction.
5) Compound A4.fwdarw.Compound A5
Compound A5 may be obtained by reacting Compound A4 with dimethoxytrityl chloride in a solvent such as pyridine, preferably at room temperature for 2 to 4 hours.
General reaction conditions for obtaining Compound A5 form Compound A4 are the same with general reaction conditions for obtaining Compound A2 from Compound A1.
6) Compound A5.fwdarw.Compound A6
Compound A6 may be obtained by reacting Compound A5 with magnesium methoxide, sodium methoxide or the like in the presence of sodium borohydride or the like as a catalyst in a benzene-methanol mixed solvent, preferably at 55.degree. to 75.degree. C. for 5 to 10 minutes.
General reaction conditions are the same with those of the [I'].fwdarw.[II'] reactions.
7) Compound A6.fwdarw.Compound A7a
Compound A7a may be obtained by reacting Compound A6 with mesyl chloride in a solvent such as pyridine, preferably at room temperature for 1 to 3 hours.
General reaction conditions for obtaining Compound A7a are the same with general reaction conditions for obtaining Compound A3 from Compound A2.
8) Compound A7a.fwdarw.Compound A8
Compound A8 may be obtained by reacting Compound A7a with sodium azide in a solvent such as dimethylformamide or diethylformamide, preferably at a temperature of 100.degree. to 120.degree. C. for 3 to 5 hours.
General reaction conditions for obtaining Compound A8 from Compound A7a are as follows.
a) Solvent
As the solvent, a solvent mainly consisting of N,N-dimethylformamide, N,N-diethylformamide or dimethylsulfoxide is used, and solvents as exemplified below may be used in combination therewith. That is, benzene, toluene, hexane, chloroform, dichloroethane, dichloromethane, ether, tetrahydrofuran, dioxane, ethyl acetate, pyridine, acetonitrile, methanol, ethanol, propanol, water, etc. may be added.
b) Reagent
An alkali metal azide compound may be used as the reagent, and sodium azide or lithium azide is preferably used.
c) Other conditions
Preferably, reaction time is 10 minutes to 20 hours, and reaction temperature is 0.degree. to 150.degree. C.
9) Compound A8.fwdarw.Compound A9
Compound A9 may be obtained by treating Compound A8 in the presence of an acid catalyst, preferably at room temperature for 2 to 4 hours to carry out hydrolysis.
General reaction conditions for obtaining Compound A9 from Compound A8 are as follows.
a) Solvent
Water, methanol, ethanol, propanol, pyridine, N,N-dimethylfomamide, dimethylsulfoxide, benzene, toluene, hexane, chloroform, dichloroethane, dichloromethane, ether, tetrahydrofuran, dioxane, ethyl acetate, acetonitrile, etc. may be used as the solvent.
b) Catalyst
Acetic acid, formic acid, hydrochloric acid, p-toluenesulfonic acid, sulfonic acid, comphorsulfonic, acid, zinc bromide, zinc chloride, an acidic ion exchange resin, etc. may be used as the catalyst. Amount of the catalyst is 0.001 mole % to a large excessive amount.
c) Other reaction conditions
Reaction time is 5 minutes to 20 hours and reaction temperature is -20.degree. to 100.degree. C.
10) Compound A6.fwdarw.Compound A7b
Acquisition of Compound A7b from Compound A6 may be attained by tosylating R.sup.3' according to a known method, for example using TsCl and Et.sub.3 N-pyridine.
11) Compound A7b43 Compound A10
The same reaction conditions as in the case of synthesis of Compound A8 from Compound A7a may be used, provided that an alkali metal iodo compound such as sodium iodide or lithium iodide, or an alkyl or aryl quaternary ammonium iodo compound such as tetra-n-butylammonium iodide is used in place of the azide compound as the reagent is used.
12) Compound A10.fwdarw.Compound A11
Compound A11 is synthesized by reacting Compound A10 with a reducing agent such as tributyltin hydride in a solvent such as toluene, preferably in the presence of azobisisobutyronitrile or light of a mercury lamp as catalysts at room temperature for 30 minutes to 6 hours.
General reaction conditions for obtaining Compound A11 from Compound A10 are as follows.
a) Solvent
Benzene, toluene, cyclohexane, hexane, methanol, ethanol, ethyl acetate, etc. may be used as a solvent.
b) Catalyst
As catalysts, a radical-generating agent such as azobisisobutyronitrile in an amount of 0.01 to 1 mole equivalent, light (preferably, that of a mercury lamp), etc. may be used.
c) Reducing agent
A metal borohydride complex containing an alkali metal or alkaline earth metal represented by sodium borohydride (NaBH.sub.4), sodium cyanoborohydride, lithium cyanoborohydride, tetraalkylammonium borohydride, diborane, an aluminum-hydrogen complex represented by lithium aluminum hydride (LiAlH.sub.4), an organotin hydride represented by tributyltin, etc. may preferably used as a reducing agent. Further, these compounds may be those heavy hydrogen- or tritium-labelled.
A reducing agent may be used preferably in an amount of 1 to 10 mole equivalent.
d) Other reaction conditions
Reaction time is preferably 5 minutes to 24 hours, and reaction temperature is preferably room temperature to 120.degree. C. Further, it is preferable to degas the solvent and to carry out the reaction under an inert gas stream.
13) Compound A11.fwdarw.Compound A12
Compound A12 may be obtained by treating Compound A11 in the presence of an acid catalyst, preferably at room temperature for 2 to 4 hours to carry out hydrolysis.
General reaction conditions for obtaining Compound A12 from Compound A11 are the same with reaction conditions for obtaining Compound A9 from Compound A8.
14) Compound C3.fwdarw.Compounds C4a, C4b and C4c
A method of synthesizing Compound C4a from Compound C3 and reaction conditions thereof are the same with the method and reaction conditions for obtaining Compound A6 from Compound A3.
General reaction conditions are the same with those of the [I'].fwdarw.[II'] reaction.
Because of a strong hygroscopic nature and difficulty of purification thereof, Compound C4a may be crystallized in methanol as picrate (C4b) or hydrochloride (C4c).
15) Compound C3.fwdarw.Compound C5
Compound C5 may be obtained by reacting Compound C3 with magnesium methoxide, preferably in a methanol-benzene solvent at a temperature of 20.degree. to 30.degree. C. for 30 minutes to 2 hours.
General reaction conditions for obtaining Compound C5 from Compound C3 are as follows:
a) Solvent
Water, methanol, ethanol, benzene, toluene, hexane, ethyl acetate, tetrahydrofuran, chloroform, ether, etc. may be used as the solvent.
b) Reagent
An alkaline compound such as a magnesium alkoxide, sodium hydroxide or potassium hydroxide is generally be used as the reagent. A magnesium alkoxide is the most preferable. When other alkaline compounds are used, temperature condition and reaction time must be controlled so that the pivaloyl group of the base alone is eliminated.
c) Other reaction conditions
Reaction time is 5 to 20 hours, and reaction temperature is 0.degree. to 100.degree. C.
16) Compound C5.fwdarw.Compound C6
Compound C6 may be obtained by reacting Compound C5 with DMTrCl in a pyridine solvent according to a known method to protect the base.
17) Compound C6.fwdarw.Compound C7
The method and reaction conditions for synthesizing Compound C7 from Compound C6 are the same with the method and reaction conditions for obtaining Compound A6 from Compound A3.
General reaction conditions are the same with the [I'].fwdarw.[II'] reaction.
18) Compound C4a or C7.fwdarw.Compound C8
Compound C8a or C8b may be obtained by reacting Compound C4a or C7 with DMTrCl or PivCl in a pyridine solvent according to a known method to protect the base and the ribose 5'-position.
19) Compound C8.fwdarw.Compound C9
Compounds C9a to C9e may be obtained by reacting Compound C8a or C8b with mesyl chloride, tosyl chloride, phenyl chlorothionocarbonate or 1,1'-thiocarbonyldiimidazole in a solvent such as pyridine, preferably at room temperature for 1 to 3 hours.
General reaction conditions of the step for obtaining Compound C9 are the same with the general reaction conditions for obtaining Compound A3 from Compound A2.
20) Compound C9.fwdarw.Compound C10
The method of synthesizing Compound C10 from Compound C9 and reaction conditions therefor are the same with the method and reaction conditions for synthesizing Compound A8 from Compound A7.
21) Compound C10.fwdarw.Compound C11
The method and reaction conditions of synthesizing Compound C11 from Compound C10 are the same with the method and reaction conditions for synthesizing Compound A9 from Compound A8.
22) Compound C9c.fwdarw.Compound C12
Compound C12 may be obtained by reacting Compound C9c, preferably, with sodium methoxide in a methanol solvent at room temperature for 24 hours.
General reaction conditions for obtaining Compound C12 from Compound C9c are as follows:
a) Solvent
A sole solvent or a mixed solvent of an alcohol such as methanol, ethanol, i-propanol or t-butanol, N,N-dimethylformamide, N,N-diethylformamide and dimethylsulfoxide may preferably used as the solvent. Benzene, ethyl acetate, hexane, tetrahydrofuran, dioxine, etc. may also be used.
b) Reagent
A metal alkoxide such as sodium methoxide or potassium t-butoxide, sodium hydroxide, potassium hydroxide, an alkali metal hydride such as sodium hydride, DBN(1,5-diazabicyclo[4,3,0]-nonene-5), DBU(1,8-diazabicyclo[5,4,0]unde-7-cene), or a metal alkylamide such as lithium diethylamide is used in an amount of 0.01 to 10 mole equivalents as the reagent.
c) Other reaction conditions
Reaction time is 10 minutes to 24 hours, reaction temperature is room temperature to 140.degree. C., and the reaction is preferably carried out an under dry, inert gas atmosphere.
23) Compound C12.fwdarw.Compound C13
Compound C13 may preferably be obtained by treating Compound C12 in a methanol solvent in the presence of hydrogen gas and palladium catalysts at room temperature for 30 minutes to one hour.
General reaction conditions for obtaining Compound C13 from Compound C12 are as follows.
a) Solvent
Methanol, ethanol, 1-propanol, water, etc. may be used as the solvent.
b) Catalyst
As the catalysts, a metal catalyst such as palladium, platinum, rhodium, ruthenium or nickel, may be used in an amount of 0.01 to 10 weight %.
c) Other reaction conditions
It is preferable that reaction time is 10 minutes to 24 hours, reaction temperature is 0.degree. to 100.degree. C. and hydrogen gas is used at 1 to 100 atoms.
24) Compound U2.fwdarw.U3, G2.fwdarw.G3, A'2.fwdarw.A'3
Preferable reaction conditions are the same with those of the A3.fwdarw.A6 reaction, and general reaction conditions are the same with those of the [I'].fwdarw.[II'] reaction.

THE BEST EMBODIMENT FOR CARRYING OUT THE INVENTION
The present invention is further specifically described below according to examples and reference example.
Reference Example 1
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-2'-O-tosyladenosine (Compound A2).
2'-O-Tosyladenosine (Compound A1) (4.21 g, 10 mmol) and 4,4'-dimethoxytrityl chloride (7.45 g, 22 mmol) were added to anhydrous pyridine (50 ml), and stirred at room temperature for 20 hours. After ice cooling, 50% aqueous pyridine was added, the mixture was extracted with chloroform, and the organic layer was washed successively with aqueous sodium bicarbonate and water, and dried over magnesium sulfate. After distillating away the chloroform, the pyridine was removed by co-evaporation with toluene, and the residue was subjected to silica gel column chromatography eluant: toluene-ethyl acetate-triethylamine.fwdarw.(9:1:0.1) toluene-ethyl acetate-triethylamine-methanol (9:1:0.1:0.2)]. Fractions containing the desired substance were combined and concentrated to give Compound A2 (7.74 g, yield 75%).
______________________________________Physical properties of Compound A2______________________________________Powders (amorphous)Elementary analysis C H N S______________________________________Calculated (%) 69.06 5.40 6.82 3.12(for C.sub.59 H.sub.55 N.sub.5 O.sub.10 S)Found (%) 68.94 5.39 6.74 3.21Specific rotations[.alpha.].sub.D.sup.24 = -39.2.degree. (c = 0.5, CHCl.sub.3)UV spectrum .lambda..sub.max.sup.MeOH 274 nm (.epsilon. 26,100)IR spectrum(KBr) 3450 1253 705 2960 1178 583 1608 1035 553 cm.sup.-1 1510 828.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.29(3H, s, C--CH.sub.3) 4.65(1H, m, H-3')3.31(1H, dd, H-5') 5.73(1H, t, H-2')3.44(1H, dd, H-5") 6.07(1H, d, H-1')3.77(12H, s, O--CH.sub.3) 7.73(1H, s, H-2)4.19(1H, m, H-4') 7.81(1H, s, H-8)______________________________________
Example 1
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(3-O-mesyl-2-O-tosyl-.beta.-D-ribofranosyl)adenine (Compound A3)
Mesyl chloride (1.45 ml, 18.6 mmol) was added to a solution of the monotosyl compound (Compound A2) (9.50 g, 9.3 mmol) in anhydrous pyridine (40 ml) at room temperature, the mixture was stirred for one hour. After cooling, 50% aqueous pyridine was added to decompose an excess of the mesyl chloride. The reaction mixture was extracted with ether, and the ether layer was washed successively with water, aqueous sodium bicarbonate and water, and dried over magnesium sulfate. After removal of the ether, the pyridine was removed under reduced pressure by co-evaporation with toluene, and the residue was subjected to silica gel column chromatography [eluant: benzene-ethyl acetate-triethylamine (95:5:1).fwdarw.benzene-ethyl acetate-triethylamine-methanol (9:5:5:1:1).] The fractions containing the desired product were combined and concentrated to afford 8.35 g of Compound A3 (yield 81%). A part thereof was dissolved in dichloromethane, and the solution was dropwise added to pentane to prepare an analytical sample.
______________________________________Physical properties of Compound A3______________________________________Powders (amorphous)Elementary analysis C H N S______________________________________Calculated (%) 66.36 5.91 5.95 5.45(for C.sub.60 H.sub.57 N.sub.5 O.sub.12 S.sub.2.C.sub.5 H.sub.12)Found (%) 66.26 6.01 5.80 5.41Specific rotations[.alpha.].sub.D.sup.20 = -34.1.degree. (c = 0.6, CHCl.sub.3)UV spectrum .lambda..sub.max.sup.MeOH 273 nm (.epsilon. 27,900)IR spectrum(KBr) 3440 1470 1180 705 2980 1370 1070 670 1610 1300 1034 580 1510 1255 830 553 cm.sup.-1.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.28(3H, s, Ts--CH.sub.3) 4.45(1H, q, H-4')3.11(3H, s, Ms--CH.sub.3) 5.44(1H, dd, H-3')3.45(1H, dd, H-5') 5.89(1H, dd, H-2')3.54(1H, dd, H-5") 6.08(1H, d, H-1')3.78(12H, s, O--CH.sub.3) 7.69(1H, s, H-2) 7.78(1H, s, H-8)______________________________________
Example 2
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(3-deoxy-.beta.-D-threo-pentofuranosyl)adenine (Compound A6)
Method 1 From Compound A3
Disulfonate (Compound A3) (110 mg, 0.1 mmol) was dissolved in a mixture of benzene (1 ml) and methanol (1 ml), and magnesium methoxide (86 mg, 1 mmol) and sodium borohydride (19 mg, 0.5 mmol) were added thereto at room temperature. The mixture was stirred at 65.degree.-70.degree. C. under an atmosphere of dry nitrogen for 4 hours. After cooling, acetone (0.5 ml) was added to inactivate an excess of the reducing agent, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed successively with an aqueous ammonium chloride and water, and dried over magnesium sulfate. The organic solvent was distilled away and the residue was subjected to silica gel column chromatography [eluant: benzene-ethyl acetate-triethylamine (9:1:0.1) benzene-ethyl acetate-triethylamine-methanol (9:1:0.1:0.1)]. Fractions containing the desired substance were concentrated to give Compound A6 (63 mg, yield 73%).
Method 2 From Compound A5
In a manner similar to Method 1, monotosyl compound (Compound A5) (102 mg, 0.1 mmol) was treated with magnesium methoxide (1 mmol)-sodium borohydride (0.5 mmol) at 65.degree. C. for 7 minutes, and Compound A6 was obtained after the column chromatography (85 mg, yield 99%).
______________________________________Physical properties of Compound A6______________________________________Powders (amorphous)Elementary analysis C H N______________________________________Calculated (%) 72.66 5.79 8.15(for C.sub.52 H.sub.49 N.sub.5 O.sub.7.0.2H.sub.2 O)Found (%) 72.84 6.08 7.87Specific rotations[.alpha.].sub.D.sup.22 = +9.2.degree. (c = 0.9, CHCl.sub.3)UV spectrum .lambda..sub.max.sup.MeOH 274 nm (.epsilon. 30,000)IR spectrum(KBr) 3440 1254 705 2970 1180 585 1610 1037 cm.sup.-1 1510 830.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.15(1H, m, H-3') 2.47(1H, m,, H-3")3.19(1H, dd, H-5') 4.53(2H, br s, H-2') and OH3.56(1H, dd, H-5") 6.06(1H, d, H-1')3.78(12H, s, O--CH.sub.3) 8.02(1H, s, H-2)4.34(1H, m, H-4') 8.24(1H, s, H-8)______________________________________
Example 3
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(3-deoxy-2-O-mesyl-.beta.-D-thereo-pentofuranosyl)adenine (Compound A7)
A solution of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(3-deoxy-.beta.-D-threo-pentofuranosyl)adenine (Compound A6) (544 mg, 0.64 mmol) in anhydrous pyridine (4 ml) was cooled with ice water, methanesulfonyl chloride (0.2 ml, 2.6 mmol) was added, and the mixture was stirred at room temperature for 5 hours. After cooling, 50% aqueous pyridine was added to decompose an excess of the reagent, and the mixture was diluted with chloroform. The organic layer was washed successively with water, aqueous sodium bicarbonate and water and dried over magnesium sulfate. The organic solvents were removed under reduced pressure. The residue was subjected to silica gel column chromatography [eluant: chloroform-methanol-triethylamine (99:1:1)] to provide 556 mg of the mesylate compound (Compound A7) (yield 93%). A part of the product was dissolved in dichloromethane and the solution was dropwise added to pentane to form a precipitate, which was then used as an analytical sample.
______________________________________Physical properties of Compound A7______________________________________Powders (amorphous)Elementary analysis C H N S______________________________________Calculated (%) 68.93 6.08 7.11 3.26(for C.sub.53 H.sub.51 N.sub.5 O.sub.9 S.0.7C.sub.5 H.sub.12)Found (%) 68.89 6.11 6.94 3.32Specific rotations[.alpha.].sub.D.sup.22 = +8.2.degree. (c = 0.9, CHCl.sub.3)UV spectrum .lambda..sub.max.sup.MeOH 274 nm (.epsilon. 29,400)IR spectrum(KBr) 3420 1367 824 2950 1250 750 1600 1173 700 1505 1030 580 cm.sup.-1.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.47(1H, m, H-3') 3.78 and 3.79(12H, s, O--CH.sub.3)2.62(1H, m, H-3") 4.34(1H, m, H-4')2.52(3H, s, C--CH.sub.3) 5.32(1H, m, H-2')3.38(1H, dd, H-5') 6.34(1H, d, H-1')3.44(1H, dd, H-5") 8.00(1H, s, H-2) 8.02(1H, s, H-8)______________________________________
Example 4
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(3-deoxy-2-O-tosyl-.beta.-D-threo-pentofuranosyl)adenine (Compound A7b)
To a solution of the deoxy compound (Compound A6) (457 mg, 0.53 mmol) in anhydrous pyridine (3 ml) was added toluenesulfonyl chloride (1.00 g, 5.3 mmol), and the mixture was stirred at room temperature for 15 hours. The reaction mixture was cooled, treated with 50% aqueous pyridine, and extracted with chloroform. The organic layer was washed successively with water, aqueous sodium bicarbonate and water, and dried over magnesium sulfate. After distilling away the chloroform, the pyridine was removed as the toluene azeotrope, and the residue was subjected to silica gel column chromatography [eluant: toluene-ethyl acetate-triethylamine (95:5:1)]. The fractions containing the desired substance were combined and concentrated to give 241 mg of the tosylated compound (Compound A7b) (yield 45%)
______________________________________Physical properties of Compound A7b______________________________________Powders (amorphous)TCL Rf = 0.70 (silica gel:chloroform-ethyl acetatemethanol (8:2; 0.2))IR spectrum(KBr) 3420 1367 1030 675 2940 1292 895 580 1600 1246 822 550 cm.sup.-1 1503 1172.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.44(1H, m, H-3') 3.77 and 3.80(12H, s, O--CH.sub.3)2.56(1H, m, H-3") 4.24(1H, m, H-4')2.15(3H, s, C--CH.sub.3) 4.88(1H, m, H-2')3.32(1H, dd, H-5') 6.03(1H, d, H-1')3.41(1H, dd, H-5") 7.80(1H, s, H-2) 7.95(1H, s, H-8)______________________________________
Example 5
Synthesis of N.sup.6 O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(2-(R)-azido-2,3-dideoxy-.beta.-D-glycero-pentofuranosyl)adenine (Compound A8)
The 3'-deoxy-2'-O-mesylated compound (Compound A7) (523 mg, 0.56 mmol) was dissolved in N,N-dimethylformamide (12 ml), and sodium azide (1.09 g, 16.8 mmol) was added thereto, followed by stirring at 105.degree.-110.degree. C. for 5 hours. The reaction mixture was cooled and extracted with ether containing a small amount of chloroform. The extract was washed several times with water and dried over magnesium sulfate. The organic solvents were removed under reduced pressure, and the residue was subjected to silica gel column chromatography [eluant: chloroform-ethyl acetate-triethylamine (97:3:1)] to give 382 mg of the azide compound (Compound A8) (yield 78%).
______________________________________Physical properties of Compound A7______________________________________Powders (amorphous)Elementary analysis C H N______________________________________Calculated (%) 70.18 5.55 12.59(for C.sub.52 H.sub.48 N.sub.8 O.sub.6.0.5H.sub.2 O)Found (%) 70.26 5.53 12.45Specific rotations[.alpha.].sub.D.sup.20 = -37.5.degree. (c = 0.4, CHCl.sub.3)UV spectrum .lambda..sub.max.sup.MeOH 274 nm (.epsilon. 28,900)IR spectrum(KBr) 3420 1505 823 2950 1248 700 2100 (N.sub.3) 1173 580 cm.sup.-1 1600 1030.sup.1 H-NMR spectrum CDCl.sub.3, .delta.2.13(1H, ddd, H-3') 4.53(1H, m, H-4')2.41(1H, m, H-3") 4.82(1H, m, H-2')3.33(1H, dd, H-5') 5.98(1H, d, H-1')3.41(1H, dd, H-5") 7.94(1H, s, H-2)3.77(12H, s, O--CH.sub.3) 8.03(1H, s, H-8)______________________________________
Example 6
Synthesis of 9-(2-azido-2,3-dideoxy-.beta.-D-glycero-pentofuranosyl)adenine (Compound A9) A mixture of the DMTr-protected 2'-azide compound (Compound A8) (182 mg, 0.21 mmol) and 80% acetic acid (6.8 ml) was stirred at room temperature for 4 hours. Acetic acid was removed under reduced pressure by co-evaporation with toluene-ethanol, and a small amount of ethanol was added to the residue to deposit the free 2'-azide compound (Compound A9) as crystals (26 mg, yield 43%). The mother liquor where the crystals had been removed was concentrated, and the residue was subjected to silica gel column chromatography [eluant: chloroform-methanol (95:5)]. The fractions containing the desired product were combined and concentrated to give Compound A9 (19 mg, yield 32%; total 75%).
______________________________________Physical properties of Compound A9______________________________________Colorless crystalsMelting point 203-204.degree. C. (dec.)Elementary analysis C H N______________________________________Calculated (%) 43.47 4.38 40.56(for C.sub.10 H.sub.12 N.sub.8 O.sub.2)Found (%) 43.47 4.38 40.60Specific rotations[.alpha.].sub.D.sup.22 = -66.0.degree. (c = 0.6, DMF)UV Spectrum .lambda..sub.max.sup.MeOH 258 nm (.epsilon. 15,000)IR Spectrum (KBr)3400 3140 2120 (N.sub.3)1695 1610 14801422 1295 11741120 1096 10681010 952 795 721 632 543 cm.sup.-1.sup.1 H-NMR Spectrum DMSO-d.sub.6, .delta.2.14(1H, m, H-3') 4.85(1H, m, H-2')2.46(1H, m, H-3") 5.25(1H, t, OH)3.54(1H, m, H-5') 6.01(1H, d, H-1')3.72(1H, m, H-5") 7.36(2H, br s, NH.sub.2)4.32(1H, m, H-4) 8.16(1H, s, H-2) 8.40(1H, s, H-8)______________________________________
Example 7
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(2(R)-iodo-2,3-dideoxy-.beta.-D-glycero-pentofuranosyl)adenine (Compound A10)
To a solution of the 2'-tosylated compound (Compound A7b) (160 mg, 0.16 mmol) in N,N-dimethylformamide (1 ml) was added lithium iodide (212 mg, 1.60 mmol) and the mixture was stirred at 105.degree.-110.degree. C. for 5 hours. After cooling, the reaction mixture was diluted with ether containing a small amount of chloroform. The solution was washed several times with water and dried over magnesium sulfate. The drying agent was removed by filtration and the filtrate was concentrated under reduced pressure. The resulting residue was subjected to silica gel chromatography [silica gel 10 g; eluant, toluene-ethyl acetate-triethylamine (30:1:0.3)] and preparative TLC [(silica gel 200.times.200.times.2 mm; developing solvent; benzene-ethyl acetate-methanol-triethylamine (9:1:0.15:0.1)] to afford 80 mg of the 2'-iodo compound (Compound A10) (yield 52%). An analytical sample was prepared by dropwise adding a dichloromethane solution of the iodo compound to pentane, followed by collecting the resulting precipitates by filtration and drying it.
______________________________________Physical properties of Compound A10______________________________________Powders (amorphous)Elementary analysis C H N______________________________________Calculated (%) 65.07 5.27 7.09(for C.sub.52 H.sub.48 N.sub.5 O.sub.6 I.0.3C.sub.5 H.sub.12)Found (%) 64.95 5.18 6.81IR Spectrum (KBr)3445 1604 1465 1174 7032955 1583 1294 1031 5842870 1507 1250 826.sup.1 H-NMR Spectrum CDCl.sub.3 .delta.2.35(1H, m, H-3') 4.99(1H, dt, H-2')2.58(1H, m, H-3") 6.42(1H, d, H-1')3.39(1H, dd, H-5') 6.77-6.86, 7.15-7.413.45(1H, dd, H-5") (27H, m, arom, NH)3.77, 3.78 and 3.79(12H, s, OMe 7.90(1H, s, H-2)4.66(1H, m, H-4') 8.03(1H, s, H-8)______________________________________
Example 8
Synthesis of N.sup.6,O.sup.5' -bis(4,4'-dimethoxytrityl)-9-(2,3-dideoxy-.beta.-D-glycero-pentofuranosyl)adenime (Compound A11)
The 2'-iodo compound (Compound A10) (217 mg, 0.22 mmol) was dissolved in previously degassed toluene (5 ml). Tributyltin hydride (91 .mu.l, 0.34 mmol) and .alpha.,.alpha.'-azobisisobutyronitrile (5 mg, 0.03 mmol) were added thereto under an atmosphere of nitrogen, and the mixture was stirred at 80.degree. C. for 20 minutes. After cooling, the reaction mixture was concentrated under reduced pressure, and the residue was purified by silica gel chromatography [silica gel 15 g; eluant, toluene-ethyl acetate-triethylamine (50:1:0.5)] to give 156 mg of the dideoxy compound (Compound A11) (yield 83%).
______________________________________Physical properties of Compound A11______________________________________AmorphousElementary analysis C H N______________________________________Calculated (%) 73.02 5.97 8.19(for C.sub.52 H.sub.49 N.sub.5 O.sub.6.0.85H.sub.2 O)Found (%) 73.32 6.05 7.89IR Spectrum (KBr) cm.sup.-13445 1605 1297 1073 7052980 1507 1250 1032 5852860 1463 1170 826.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.2.05(2H, m, H-3') 6.27(1H, dd, H-1')2.49(2H, m, H-2') 6.76-6.723.32(2H, d, H-5') (8H, each, d, arom H)3.76(12H, s, OMe) 6.88(1H, s, NH)4.33(1H, m, H-4') 7.18-7.43(18H, m, arom) 7.94(1H, s, H-2) 8.04(1H, s, H-8)______________________________________
Reference Example 2
Synthesis of 9-(2,3-dideoxy-.beta.-D-glyceropentofuranosyl)adenine(dideoxyadenosine) (Compound A12)
The dimethoxytrityl-protected 2',3'-dideoxy compound (Compound A11) (65 mg, 0.077 mmol) was dissolved in chloroform (385 .mu.l,) and a solution of zinc bromide (ZnBr.sub.2 141 mg, 0.62 mmol) in methanol (182 .mu.l)--chloroform (676 .mu.l) was added thereto, followed by stirring at room temperature for about 4 hours. After completion of the reaction methanol (2 ml) was added and chloroform was distilled off under reduced pressure with such precaution that the reaction solution is not evaporated to dryness. Water was added to the resulting methanol solution, the resulting precipitate of trityl alcohol was removed by filtration and the filtrate was passed through a HP-20 column (10.times.130 mm) (eluant; water--30% methanol). The fractions containing the desired substance were concentrated under reduced pressure, and the residue was purified using Domex 1-X2 (OH.sup.- form, eluant; methanol) and recrystallized from ethanol to afford the desired dideoxyadenosine (Compound A12) as colorless crystals. Yield 8 mg (44%).
Compound A12 is the known compound, and its physical properties are disclosed in M. J. Robins, J. R. McCarthy, R. K. Robins, Biochem., 5, 224 (1966).
______________________________________Physical properties of Compound A12______________________________________Melting point 185-186.degree. C.NMR Spectrum (D.sub.2 O) .delta. from DSS2.04(1H, m, H-3') 4.36(1H, m, H-4')2.23(1H, m, H-3") 6.29(1H, dd, H-1')2.52(1H, m, H-2') 8.18(1H, s, H-2)2.57(1H, m, H-2") 8.30(1H, s, H-8)3.66(1H, dd, H-5')3.82(1H, dd, H-5")______________________________________
Example 9
Synthesis of N.sup.4,O.sup.2',O.sup.5' -tripivaloyl-3'-O-methanesulfonylcytosine (Compound C3)
Pivaloyl chloride (19.8 ml, 160 mmol) was added all at once to a solution of cytidine (972 g, 40 mmol) in pyridine (140 ml) under ice cooling, followed by stirring at room temperature for 90 minutes. Then, methanesulfonyl chloride (186 ml, 240 mmol) was added under ice cooling, followed by stirring at room temperature for one hour. After cooling, an aqueous 50% pyridine solution was added to decompose an excess of the reagent, and the mixture was extracted with ether. The organic layer was washed successively with aqueous sodium bicarbonate and aqueous saturated sodium chloride, and dried over magnesium sulfate. After evaporating the solvent under reduced pressure, the remaining pyridine was removed by coevaporation with toluene, and the residue was subjected to silica gel column chromatography [eluant, benzene-ethyl acetate (2:1)] to give 18.3 g of the desired 3'-mesylated compound (Compound C3) (yield 80%). An analytical sample was prepared by dropwise adding a dichloromethane solution of Compound C3 to n-pentane and drying the resulting precipitates.
______________________________________Physical properties of Compound C3______________________________________AmorphousElementary analysis C H N S______________________________________Calculated (%) 52.02 6.88 7.28 5.55(for C.sub.25 H.sub.39 N.sub.3 O.sub.10 I.0.2H.sub.2 O)Found (%) 51.93 6.80 7.21 5.55IR Spectrum (KBr)cm.sup.-13450 2705 1632 1315 1142 5303380 1736 1557 1280 9753000 1720 1483 1180 9282960 1670 1370 1140 845.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.1.26(9H, s, C(CH.sub.3).sub.3) 5.30(1H, t, H-3')1.27(9H, s, C(CH.sub.3).sub.3) 5.49(1H, dd, H-2')1.29(9H, s, C(CH.sub.3).sub.3) 6.01(1H, d, H-1')3.07(3H, s, SO.sub.2 CH.sub.3) 7.47(1H, d, H-5)4.44(2H, d, H-5', H-5") 7.82(1H, d, H-6)4.52(1H, m, H-4') 8.19(1H, br s, NH)______________________________________
Reference Example 3
Synthesis of 1-(3-deoxy-.beta.-D-threo-pentofuranosyl) cytosine (Compound C4a, C4b and C4c)
Compound C3 (241 g, 4.20 mmol) was dissolved in a mixture of benzene (4 ml) and methanol (4 ml), and magnesium methoxide (1.19 g, 13.8 mmol) and sodium borohydride (321 mg, 8.49 mmol) were added at room temperature, followed by stirring for 10 hours. After cooling, acetone (2 ml) was added to decompose an excess of the reagent, an aqueous ammonium chloride solution was added, and the deposited precipitates were removed by filtration. The filtrate was partitioned between ethyl acetate and water, and the ethyl acetate layer was further washed twice with water. The thus obtained water layer was passed through a column packed with HP-20 (Dowex Co., styrene-divinylbenzene polymer, 50 ml) to adsorb by-products, and the desired C4a product was eluted with water (about 1 l). Then, an activated carbon (50 ml, Wako Junyaku Co., Ltd., for column choromatography) was added to this aqueous solution, followed by stirring for 20 minutes. The activated carbon was separated by filtration, and after washing with water the adsorbed organic substance was eluted with methanol to provide the desired 3'-deoxy threo compound (C4a) along with its erythro isomer (786 mg, yield 83%, threo:erythro=93:7). Since Compound C4a has a strong hygroscopic property and is hard to be purified, it was crystallized from methanol as the picrate (C4b) or as the hydrochloride (C4c).
______________________________________Physical properties of Compound C4aAmorphousIR Spectrum (KBr)cm.sup.-13380 1490 11232960 1395 10631647 1289 7861605 1200 600.sup.1 H-NMR Spectrum (DMSO-d.sub.6) .delta.1.74(1H, ddd, H-3') 5.67(1H, d, H-5)2.27(1H, ddd, H-3") 5.88(1H, d, H-1')3.55(1H, m, H-5') 7.68(1H, d, H-6)3.99-4.04(1H, m, H-4') 6.9-7.1(2H, brs, NH.sub.2)4.24-4.29(1H, m, H-2')5.08(1H, m, OH)5.18(1H, d, OH)Physical properties of Compound C4bMelting point 208-209.degree. C. (dec.)IR Spectrum (KBr) cm.sup.-13600 1695 1550 1120 8203350 1675 1335 1082 7903130 1610 1315 1035 7402980 1575 1265 910 710 623.sup.1 H-NMR Spectrum (DMSO-d.sub.6) .delta.1.75(1H, m, H-3') 6.05(1H, d, H-5)2.26(1H, m, H-3") 8.13(1H, d, H-6)3.60(2H, m, H-5',5") 8.59(2H, s, arom)4.08(1H, m, 4') 9.45(1H, br s, N.sup.+ --H)4.40(1H, m, H-2')5.19(1H, d, H-1')Physical properties of Compound C4cMelting point 183.5-184.5.degree. (dec.)Elementary analysis C H N S______________________________________Calculated (%) 41.00 5.35 15.94 13.45(for C.sub.19 H.sub.13 N.sub.3 O.sub.4.HCl)Found (%) 41.00 5.38 15.90 13.55Specific rotations[.alpha.].sub.D.sup.26 +151.degree. (c = 0.5, H.sub.2 O)IR Spectrum (KBr) cm.sup.-13460 1700 1382 1072 7803240 1675 1284 982 7003040 1635 1118 930 6092750 1540 1092 810 590______________________________________
Example 10
Synthesis of 2',5'-di-O-pivaloyl-3'-O-methanesulfonylcytidine (Compound C5)
Compound C3 (667 mg, 1.16 mmol) was dissolved in a mixture of benzene (1 ml) and methanol (1 ml), and magensium methoxide (150 mg, 1.74 mmol) was added to this solution, followed by stirring at room temperature for 30 minutes. The reaction mixture was cooled, an aqueous saturated ammonium chloride solution was added, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed twice with saturated aqueous sodium chloride and dried over magnesium sulfate. The solvents were evaporated under reduced pressure and the residue was subjected to silica gel column chromatography [eluant; chloroform-methanol (50:1)] to give Compound C5 (495 mg, yield 87%).
An analytical sample was prepared by dropwise adding a dichloromethane solution of Compound C5 to pentane and drying the resulting precipitates.
______________________________________Physical properties of Compound C5______________________________________AmorphousElementary analysis C H N S______________________________________Calculated (%) 49.07 6.38 8.58 6.55(for C.sub.20 H.sub.31 N.sub.3 O.sub.9 S)Found (%) 48.95 6.34 8.49 6.50Specific rotations[.alpha.].sub.D.sup.20 +41.8.degree. (c = 0.3, CHCl.sub.3)IR Spectrum (KBr) cm.sup.-13370 1650 1180 9303000 1484 1145 7902960 1369 1040 5321736 1285 975NMR Spectrum (CDCl.sub.3) .delta.1.24(9H, s, C(CH.sub.3).sub.3) 5.72(1H, d, H-1')1.26(9H, s, C(CH.sub.3).sub.3) 5.87(1H, d, H-5)3.08(3H, s, SO.sub.2 CH.sub.3) 7.38(1H, d, H-6)4.47-4.35(3H, m, H-4', H-5', H-5")5.40(1H, t, H-3')5.49(1H, dd, H-2')______________________________________
Example 11
Synthesis of N.sup.4 -(4,4'-dimethoxytrityl)-2',5'-di-O-pivaloyl-3'-O-methanesulfonylcytidine (Compound C6)
4,4'-Dimethoxytrityl chloride (685 mg, 2.02 mmol) was added to a solution of Compound C5 (825 mg, 1.69 mmol) in anhydrous pyridine (4 ml) and the mixture was stirred at room temperature for 3 hours. After cooling, aqueous 50% pyridine was added to decompose an excess of the reagent, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed with aqueous sodium bicarbonate and dried over magnesium sulfate. The organic solvents were evaporated, the remaining pyridine was removed as the toluene azeotrope and the residue was subjected to silica gel chromatography [eluant; chloroform-ethyl acetate-triethylamine (80:20:1)] to give 1.280 g of the desired compound, C6 (yield 96%).
An analytical sample was prepared by dropwise adding a dichloromethane solution of Compound C6 to pentane and drying the resulting precipitates.
______________________________________Physical properties of Compound C6______________________________________AmorphousElementary analysis C H N S______________________________________Calculated (%) 61.49 6. 29 5.25 4.00(for C.sub.41 H.sub.49 N.sub.3 O.sub.11 S.0.5H.sub.2 O)Found (%) 61.61 6.21 5.25 3.97Specific rotations[.alpha.].sub.D.sup.20 +4.0.degree. (c = 0.5, CHCl.sub.3)IR Spectrum (KBr) cm.sup.-13430 1662 1497 1180 7792990 1653 1365 1144 7022950 1635 1280 1032 5871735 1506 1256 829 525.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.1.14(9H, s, C(CH.sub.3).sub.3) 5.32(1H, br t, H-3')1.26(9H, s, C(CH.sub.3).sub.3) 5.53(1H, dd, H-2')3.05(3H, s, S--CH.sub.3) 5.73(1H, d, H-1')3.80(3H, s, O--CH.sub.3) 6.82(5H, br d)4.32-4.42(3H, m) 7.08-7.33(10H, m)5.05(1H, d, H-5)______________________________________
Example 12
Synthesis of N.sup.4 -(4,4'-dimethoxytrityl)-1-(3-deoxy-.beta.-D-threo-pentofuranosyl)cytosine (Compound C7)
Compound C6 (50 mg, 0.063 mmol) was dissolved in a mixture of benzene (0.5 ml) and methanol (0.5 ml), and magnesium methoxide (27 mg, 0.313 mmol) and sodium borohydride (12 mg, 0.317 mmol) were added, followed by stirring for 10 hours. After cooling acetone (0.1 ml) was added to decompose an excess of the reagents, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed with aqueous sodium bicarbonate and dried over magnesium sulfate. The organic solvents were evaporated, the remaining pyridine was removed as the toluene azeotrope, and the residue was subjected to silica gel column chromatography (eluant; chloroform-methanol-triethylamine (100:2:1)) to afford the desired 3'-deoxy threo compound C7 and its epimer, erythro compound (total 30 mg) (yield 90%, threo:erythro=93:7).
The compound is C7 difficult for separation from its epimer, and was used, without purification, for further reaction.
Example 13
Synthesis of N.sup.4 -(4,4'-dimethoxytrityl)-1-(3-deoxy-.beta.-D-threo-pentofuranosyl)cytosine (Compound C7)
Reaction was carried out in a manner similar to that in Example 12 using Compound C6 (236 mg, 0.298 mmol) and magnesium methoxide (129 mg, 1.494 mmol). Tetra-n-butylammonium borohydride (383 mg, 1.488 mmol) was used in place of sodium borohydride. As the result, 142 mg of the desired 3'-deoxy threo compound C7 and an erthro isomer were obtained (yield 90%, threo compound:erythro=93:7).
______________________________________Physical properties of Compound C7______________________________________AmorphousIR Spectrum (KBr) cm.sup.-13400 1250 8302950 1180 7821635 1115 7021505 1030 585NMR Spectrum (CDCl.sub.3) .delta.2.02(1H, m, H-3') 4.28(1H, m, H-4')2.39(1H, m, H-3") 4.57(1H, m, H-2')3.63(1H, dd, H-5') 5.07(1H, d, H-5)3.79 and 3.80(6H, each, s, OCH.sub.3) 5.90(1H, d, H-1')3.88(1H, dd, H-5") 6.80-6.85, 7.12-7.30 (m, arom) 7.57(1H, d, H-6)______________________________________
Example 14
Synthesis of N.sup.4,O.sup.5' -bis(4,4'-dimethoxytrityl)-1-(3-deoxy-.beta.-D-threo-pentofuranosyl)cytosine (Compound C8a)
The mono DMTr compound (Compound C7, 530 mg, 1.0 mmol) was dissolved in anhydrous pyridine (5 ml), and 4,4'-dimethoxytrityl chloride (407 mg, 1.2 mmol) was added thereto, followed by stirring at room temperature for 2 hours. After cooling, 50% aqueous pyridine was added to decompose an excess of the reagent, and the mixture was extracted with ether. The organic layer was washed successively with aqueous sodium bicarbonate and water, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The pyridine was removed as the toluene azeotrope. The residue was subjected to silica gel chromatography [eluant; benzene-ethyl acetate-triethylamine-methanol (50:50:1:1)], and the fractions containing the desired substance were combined and concentrated to give 594 mg of the di-DMTr compound (Compound C8a) (yield 71%).
______________________________________Physical properties of Compound C8a______________________________________AmorphousElementary analysis C H N______________________________________Calculated (%) 73.45 6.16 5.04(for C.sub.51 H.sub.51 N.sub.3 O.sub.8)Found (%) 73.20 6.46 4.79Specific rotations[.alpha.].sub.D.sup.25 = +17.1.degree. (c = 1.1, CHCl.sub.3)TLC Rf = 0.53 (Silica gel; CHCl.sub.3 --MeOH (9:1))UV spectrum .lambda..sub.max.sup.MeOH 281 nm (.epsilon. 17,400)IR spectrum (KBr) cm.sup.-13420 1643 1180 7022960 1510 1034 5842850 1252 830.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.2.04(1H, m, H-3') 4.15(1H, m, H-4')2.20(1H, m, H-3") 4.68(1H, m, H-2')3.28(1H, dd, H-5') 4.82(1H, d, H-5)3.41(1H, dd, H-5") 5.98(1H, d, H-1')3.73, 3.74 and 3.75 6.72-7.34 (m, arom)(12H, each s, O--CH.sub.3) 7.90(1H, d, H-6)______________________________________
Example 15
Synthesis of N.sup.4,O.sup.5' -dipivaloyl-1-(3-deoxy-.beta.-D-threo-pentofuranosyl)cytosine (Compound C8b)
The diol compound (Compound C4a, 180 mg, 0.799 mmol), prepared according to the method (Example 10), was dissolved in anhydrous pyridine (2 ml), and pivaloyl chloride (230 .mu.l, 1.87 mmol) was added thereto, followed by stirring at room temperature for 6 hours. After cooling, water was added to decompose an excess of the reagent, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed successively with aqueous sodium bicarbonate and aqueous saturated sodium chloride, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The pyridine was removed as the toluene azeotrope and the residue was subjected to silica gel column chromatography [eluant; chloroform-methanol (50:1)] to provide 250 mg of the desired dipivaloylated compound (Compound C8b) (yield 79%) and its erythro isomer (25 mg, yield 8%).
______________________________________Physical properties of Compound C8b______________________________________Colorless crystalsMelting point 150-151.degree. C.Elementary analysis C H N______________________________________Calculated (%) 57.71 7.39 10.63(for C.sub.19 H.sub.29 O.sub.6 N.sub.3.HCl)Found (%) 57.64 7.34 10.58Specific rotations[.alpha.].sub.D.sup.24 = +134.degree. (c = 0.5, CHCl.sub.3)IR Spectrum (KBr) cm.sup.-13450 1648 1395 1128 9203000 1618 1310 1100 8032900 1558 1278 1035 6251716 1485 1157 1015.sup.1 H-NMR Spectrum (CDCl.sub.3)1.26(9H, s, C(CH.sub.3).sub.3) 4.52(1H, dd, H-5")1.29(9H, s, C(CH.sub.3).sub.3) 4.88(1H, ddd, H-2')1.8-2.1(1H, br s, OH) 5.97(1H, d, H-1')1.95(1H, ddd, H-3') 7.46(1H, d, H-5)2.43(1H, ddd, H-3") 8.10(1H, d, H-6)4.21(1H, dd, H-5') 8.20(1H, br s, NH)4.42-4.45(1H, m, H-4')______________________________________
Example 16
Synthesis of N.sup.4,O.sup.5' -bis(4,4'-dimethoxytrityl)-1-(3-deoxy-2-O-mesyl-.beta.-D-threo-pentofuranosyl)cytosine (Compound C9a)
Methanesulfonyl chloride (0.132 ml, 1.7 mmol) was added to a solution of Compound C8a (470 mg, 0.56 mmol) in anhydrous pyridine (3 ml) and the mixture was stirred for 4.5 hours. After cooling, ice water was added to decompose an excess of the reagent, and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed successively with water, aqueous sodium bicarbonate and water, and dried over magnesium sulfate. The organic solvents were evaporated, the remaining pyridine was removed as the toluene azeotrope, and the residue was subjected to silica gel column chromatography [eluant; benzene-ethyl acetate-triethylamine-methanol (50:50:1:3)] to give 406 mg (yield 79%) of the mesylated compound (Compound C9a). An analytical sample was prepared by dropwise adding a dichloromethane solution of this mesylated compound to pentane and drying the resulting precipitates.
______________________________________Physical properties of Compound C9a______________________________________AmorphousElementary analysis C H N S______________________________________Calculated (%) 69.56 6.66 4.27 3.26(for C.sub.52 H.sub.53 N.sub.3 O.sub.10 S.C.sub.5 H.sub.12)Found (%) 69.43 6.69 4.14 3.27Specific rotations[.alpha.].sub.D.sup.25 = +27.6.degree. (c = 1.0, CHCl.sub.3)TLC Rf = 0.58 (Silica gel; CHCl.sub.3 --MeOH (9:1))UV spectrum .lambda..sub.max.sup.MeOH 276 nm (.epsilon. 19,400)IR spectrum (KBr) cm.sup.-13450 1660 1177 827 5302970 1510 1032 7052860 1250 906 587.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.2.28(1H, ddd, H-3') 4.17(1H, m, H-4')2.49(1H, ddd, H-3") 5.31(1H, q, H-2')2.88(3H, s, C--CH.sub.3) 4.96(1H, d, H-5)3.30(2H, br s, H-5', 5")6.11(1H, d, H-1') 7.56(1H, d, H-6).3.74, 3.75, 3.76 and 6.75-7.36(m, arom.)3.77(12H, each s, O--CH.sub.3)______________________________________
Example 17
Synthesis of N.sup.4,O.sup.5' -bis(4,4'-dimethoxytrityl)-1-(3-deoxy-2-O-tosyl-.beta.-D-threo-pentofuranosyl)cytosine (Compound C9b)
Compound C8a (250 mg, 0.30 mmol) was dissolved in anhydrous tetrahydrofuran (2 ml), and a t-butylmagnesium chloride-THF solution (1.7M, 360 l, 0.61 mmol) and then p-toluenesulfonyl chloride (172 mg, 0.90 mmol) were added, followed by stirring at room temperature for 22 hours. The reaction mixture was poured in aqueous 2% sodium bicarbonate, and extracted with toluene. The extract was washed successively with aqueous saturated sodium bicarbonate and water, and dried over magnesium sulfate. Magnesium sulfate was removed by filtration, the filtrate was concentrated under reduced pressure, and the residue was purified by silica gel chromatography [10 g, eluant; chloroform-methanol-triethylamine (50:1:0.5)] to give 290 mg (yield 97%) of the 2'-tosylated compound (Compound C9b) as colorless glasses.
______________________________________Physical properties of Compound C9b______________________________________AmorphousIR Spectrum (KBr) cm.sup.-13430 1652 1172 8252960 1505 1030 6992860 1245 895 580.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.2.17(1H, m, H-3') 4.92(1H, m, H-2')2.41(1H, m, H-3") 5.00(1H, d, H-5)2.44(3H, s, Ts) 6.00(1H, d, H-1')3.25(2H, m, H-5) 6.76-7.383.77, 3.75, 3.74 (31H, m, arom, NH)(12H, each s, OMe) 7.55 (1H, d, H-6)4.14(1H, m, H-4')______________________________________
Example 18
Synthesis of N.sup.4,O.sup.5' -dipivaloyl-1-(3-deoxy-2-O-tosyl-.beta.-D-threo-pentofuranosyl)cytosine (Compound C9c)
Compound C8b (1.684 g, 4.28 mmol) was dissolved in dry tetrahydrofuran (15 ml), and sodium hydride (purity 60%, 257 mg, 6.92 mmol) was added under ice cooling, followed by stirring for 15 minutes. Further, p-toluenesulfonyl chloride (1.63 g, 8.39 mmol) was added and the mixture was stirred at room temperature for 3 hours. Ice water was added to quench the reaction and the mixture was extracted with ether containing a small amount of chloroform. The organic layer was washed successively with aqueous sodium bicarbonate and aqueous saturated sodium chloride, and dried over magnesium sulfate. The organic solvents were evaporated and the residue was subjected to silica gel column chromatography [eluant; chloroform-methanol (100:1)] to afford 1.73 g (yield 74%) of the desired tosylated compound C9c.
______________________________________Physical properties of Compound C9c______________________________________Colorless crystalsMelting point 175-176.degree. C.Elementary analysis C H N S______________________________________Calculated 56.82 6.42 7.65 5.83(for C.sub.26 H.sub.35 N.sub.3 O.sub.8 S)Found (%) 56.78 6.48 7.55 5.70Specific rotations[.alpha.].sub.D.sup.24 +109.degree. (c = 0.6, CHCl.sub.3)IR Spectrum (KBr) cm.sup.-13450 1733 1626 1312 9023000 1718 1558 1180 8142950 1673 1486 1026 663.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.1.23(9H, s, C(CH.sub.3).sub.3) 5.24(1H, ddd, H-2')1.31(9H, s, C(CH.sub.3).sub.3) 5.99(1H, d, H-1')2.26(1H, ddd, H-3') 7.25-7.6(4H, m, arom)2.42(3H, s, ArMe) 7.60(1H, d, H-5)2.58(1H, ddd, H-3") 7.87(1H, d, H-6)4.22(1H, dd, H-5')4.35-4.43(2H, m, H-5", H-4')______________________________________
Example 19
Synthesis of N.sup.4,O.sup.5' -dipivaloyl-1-(3-deoxy-2-O-phenoxythiocarbonyl-.beta.-D-threo-pentofuranosyl)cytosine (Compound C9d)
Compound C8b (100 mg, 0.25 mmol) was dissolved in acetonitrile (2 ml), and N,N-dimethylaminopyridine (80 mg, 0.66 mmol) and phenyl chlorothionocarbonate (40 l, 0.33 mmol) were added, followed by stirring at room temperature for 20 hours. Water was added to the reaction mixture and extracted with chloroform, and the organic layer was washed successively with water, aqueous saturated sodium bicarbonate and water, and dried over magnesium sulfate. The drying agent was removed by filtration, the filtrate was concentrated under reduced pressure, and the residue was purified by preparative TLC [200.times.200.times.2 mm, developing solvent; chloroform-methanol (9:1)] to give 73 mg of Compound C9d as colorless glasses (yield 53%).
______________________________________Physical properties of Compound C9d______________________________________AmorphousIR Spectrum (film) cm.sup.-13420 1638 12703000 1557 12051732 1488 11251715 1398 7991671 1310 735.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.1.26(9H, s, piv) 6.03(1H, m, H-2')1.30(9H, s, piv) 6.28(1H, d, H-1')2.29(1H, m, H-3') 6.98(1H, d, H-5)2.75(1H, m, H-3") 7.24-7.48(5H, m, Ph)4.35(2H, m, H-5') 7.98(1H, d, H-6)4.48(1H, m, H-4') 8.13(1H, br s, amide)______________________________________
Example 20
Synthesis of N.sup.4,O.sub.5' -dipivaloyl-1-(3-deoxy-2-O-imidazoylthiocarbonyl-.beta.-D-threo-pentofuranosyl)cytosine (Compound C9e)
Compound C8b (80 mg, 0.20 mmol) and 1,1'-thiocarbonyldiimidazole (50 mg, 0.28 mmol) were dissolved in acetonitrile (1 ml) and the solution was stirred at room temperature for 20 hours. The organic solvent was evaporated and the residue was subjected to silica gel column chromatography [eluant; chloroform-methanol (50:1)] to afford 83 mg of the desired compound C9e (yield 81%).
______________________________________Physical properties of Compound C9e______________________________________Amorphous.sup.1 H-NMR Spectrum (CDCl.sub.3)1.21(9H, s, C(CH.sub.3).sub.3) 6.20(1H, d, H-1')1.28(9H, s, C(CH.sub.3).sub.3) 6.25(1H, m, H-2')2.19(1H, ddd, H-3') 7.01, 7.412.83(1H, ddd, H-3") (2H, each, m, arom.)4.14(1H, dd, H-5') 7.55(1H, d, H-5)4.47-4.53 8.10(1H, brs, NH)(2H, m, H-41, H-5") 8.12(1H, d, H-6) 8.12(1H, s, arom.)______________________________________
Example 21
Synthesis of N.sup.4,O.sup.5' -bis(4,4'-dimethoxytrityl)-1-[(2R)-2-azido-2,3-dideoxy-.beta.-D-glycero-pentofuranosyl]cytosine (Compound C10)
The 3'-deoxy-2'-O-mesyl compound (Compound C9a) (287 mg, 0.32 mmol) was dissolved in N,N-dimethylformamide (4 ml), and sodium azide (102 mg, 1.58 mmol) was added thereto, followed by stirring at 115.degree.-120.degree. C. for 4 hours. The reaction mixture was cooled and extracted with ether, and the extract was washed several times with water and dried over magnesium sulfate. The ether was removed and the residue was subjected to silica gel chromatography [eluant; benzene-ethyl acetate-triethylamine-methanol (50:50:1:0.2)] to give 251 mg of the azide compound (Compound C10) (yield 93%).
______________________________________Physical properties of Compound C10______________________________________AmorphousElementary analysis C H N______________________________________Calculated (%) 71.31 5.87 9.79(for C.sub.51 H.sub.50 N.sub.6 O.sub.7)Found (%) 71.11 5.86 9.52Specific rotations[.alpha.].sub.D.sup.25 = -31.0.degree. (c = 0.9, CHCl.sub.3)TLC Rf = 0.66 Silica gel[benzene-ethyl acetate-methanol (1:1:0.1)]UV spectrum .lambda..sub.max.sup.MeOH 281 nm (.epsilon. 19,900)IR spectrum (KBr) cm.sup.-13430 2110(N.sub.3) 1248 1033 5852980 1655 1175 8252850 1505 1102 702.sup.1 H-NMR Spectrum (CDCl.sub.3) .delta.1.77(1H, dd, H-3') 4.27(1H, d, H-2')2.04(1H, m, H-3") 4.72(1H, d, H-5)3.30(1H, dd, H-5') 5.89(1H, br s, H-1')3.54(1H, dd, H-5") 6.7-7.3(m, arom.)3.73 and 3.74 7.84(1H, d, H-6)(12H, each s, CH.sub.3)4.35(1H, m, H-4')______________________________________
Reference Example 4
Synthesis of 1-[(2R)-2-azido-2,3-dideoxy-.beta.-D-glyceropentofuranosyl]cytosine (Compound C11)
A mixture of the DMTr-protected 2'-azido compound (Compound C10) (171 mg, 0.20 mmol) and 80% acetic acid (3 ml) was stirred at 50.degree.-55.degree. C. for 75 minutes. The acetic acid was removed under reduced pressure and azeotropy using toluene-ethanol, and a small amount of dichloromethane was added to the residue to deposit the free 2'-azide compound (Compound C11) as crystals (42 mg, yield 84%). An analytical sample was obtained by recrystallization from isopropyl alcohol.
______________________________________Physical properties of Compound C11______________________________________Melting point 171-172.degree. C. (dec.)Elementary analysis C H N______________________________________Calculated (%) 42.55 4.84 33.08(for C.sub.9 H.sub.12 N.sub.6 O.sub.3.0.1H.sub.2 O)Found (%) 42.48 4.75 33.02Specific rotations[.alpha.].sub.D.sup.25 = -42.6.degree. (c = 0.3, DMF)UV spectrum .lambda..sub.max.sup.MeOH 271 nm (.epsilon. 8,900)IR spectrum (KBr) cm.sup.-13480 2130(N.sub.3) 1620 1105 7053300 1680 1500 970 5953100 1656 1290 8532970 1639 1250 780.sup.1 H-NMR Spectrum (DMSO-d.sub.6) .delta.1.81(1H, ddd, H-3') 5.14(1H, t, OH)2.00(1H, ddd, H-3") 5.70(1H, d, H-5)3.56(1H, ddd, H-5') 5.72(1H, d, H-1')3.78(1H, ddd, H-5") 7.14(2H, br d, NH.sub.2)4.20(1H, m, H-4') 7.96(1H, d, H-6)4.32(1H, br d, H2')______________________________________
Reference Example 5
Synthesis of 1-(2,3-dideoxy-.beta.-D-glycero-pent-2'-enofuranosyl)cytosine (Compound C12)
Method 1
A 25 weight % sodium methoxide-methanol solution (175 l) was added to a solution of the tosylated compound C9c (84 mg, 0.153 mmol) in methanol (2 ml), and the mixture was stirred under reflux for 24 hours. After cooling, aqueous saturated ammonium chloride was added to quench the reaction, and the by-products were extracted with ethyl acetate and removed. An activated carbon (manufactured by WAKO JUNYAKU Co., Ltd., for chromatography, 10 ml) was added to the resulting water layer to adsorb the organic matters. The resulting activated carbon was washed with water Elution with methanol gave 2.5 mg of the unsaturated compound C12 (yield 7.8%).
Method 2
The tosylated compound C9c (53 mg, 0.097 mmol) and potassium tert-butoxide (54 mg, 0.48 mmol) were dissolved in tert-butyl alcohol (1 ml), and the solution was stirred at 60.degree. C. for 30 minutes. The reaction mixture was poured in aqueous saturated ammonium chloride and extracted with ethyl acetate. The organic layer was washed with aqueous saturated sodium chloride, dried over magnesium sulfate, and concentrated under reduced pressure. Saturated aqueous ammonia-methanol (1 ml) was added to the residue and the mixture was stirred at room temperature for 24 hours. The methanol was evaporated under reduced pressure and the residue was purified by silica gel column chromatography to give 16 mg of the desired unsaturated compound C12 (yield 79%).
Method 3
The same procedure as described in Method 2 was carried out except that sodium hydride (oil, purity 60%, 19 mg, 0.48 mmol) was used in place of potassium tert-butoxide. As the result, 10 mg of the desired unsaturated compound was obtained (yield 49%).
______________________________________Physical properties of Compound C12______________________________________.sup.1 H-NMR Spectrum (DMSO-d.sub.6) .delta.3.57(2H, m, H-5', H-5") 6.89(1H, m, H-1')4.76(1H, m, H-4') 7.14(2H, br d, NH.sub.2)4.9.5(1H, t, OH) 7.68(1H, d, H-6)5.70(1H, d, H-5)5.87(1H, m, H-3')6.33(1H, m, H-2')______________________________________
Reference Example 6
Synthesis of 1-(2,3-dideoxy-.beta.-D-glyceropentofuranosyl)cytosine (dideoxycytidine) (Compound C13)
The reduction was carried out according to the method of Horwitz et al. (J. P. Horwitz, J. Chua, M. Noel, and J. T. Donatti, J. Org. Chem., 32, 817 (1967)). The unsaturated compound C12 (50 mg, 0.239 mmol) and 5% palladium-carbon (10 mg) in methanol (3 ml) was stirred under a hydrogen atmosphere for one hour. After removal of the insoluble materials by filtration, the solvent was evaporated under reduced pressure and the resulting residue was purified by silica gel column chromatography [eluant; chloroform-methanol (8:2)] to obtain mg of the desired dideoxycytidine C13 (yield 71%).
______________________________________Physical properties of Compound C13______________________________________.sup.1 H-NMR Spectrum (DMSO-d.sub.6)1.72-1.89(3H, m, H-2', H-3', H-3") 7.10(2H, br d, NH.sub.2)2.21-2.30(1H, m, H-2") 7.92(1H, d, H-6)3.54(1H, m, H-5')3.68(1H, m, H-5")4.01(1H, m, H-4')5.05(1H, t, OH)5.72(1H, d, H-5)5.93(1H, dd, H-1')______________________________________
Example 22
Synthesis of 1-(3-deoxy-.beta.-D-threo-pentofuranosyl)uracil (Compound U3)
Pivaloyl chloride (9.08 g, 75 mmol) was added to a solution of uridine (7.32 g, 30 mmol) in dry pyridine (100 ml) at 5.degree. C., and the mixture was then stirred at room temperature for 30 minutes. After the reaction mixture had been cooled to 5.degree. C., mesyl chloride (13.8 g, 120 mmol) was added thereto and stirred at room temperature for one hour. The reaction mixture was cooled again and the reaction was quenched with 50% aqueous pyridine. The product was extracted with ether containing a small amount of chloroform. The extract was washed with water, aqueous sodium bicarbonate, and then water, and dried over magnesium sulfate. The organic solvent was removed. The pyridine was removed by toluene azeotropic evaporation. The residue was dissolved in methanol (100 ml) and cooled to 5.degree. C. A solution of potassium hydroxide (6.72 g, 120 mmol) in methanol (80 ml) was added thereto with stirring, and then immediately sodium borohydride (2.28 g, 60 mmol) was added thereto.
After the reaction mixture had been stirred at room temperature for 24 hours, the insoluble crystals were collected by filtration with through a Celite pad and washed with methanol.
The filtrate and the washings were combined and cooled to 5.degree. C. A mixture of concentrated hydrochloric acid (9.8 ml, ca. 118 mmol) and methanol (37 ml) was added thereto. The precipitate was colledted by filtration through a Celite pad and washed with methanol. The filtrate and washings were combined, concentrated to 40 ml, and cooled. Then a mixture of concentrated hydrochloric acid (2.1 ml) and methanol (10 ml) was added again and the insoluble materials were collected by filtration and washed with methanol. The filtrate and washings were concentrated and the water was removed three times by ethanol azeotropic co-evaporation. The residue was subjected to silica gel column chromatography [eluant: chloroform-methanol (99:1)] and the objective compound (Compound U3) (3.82 g, 56%) was eluted with the same solvent system (97:3.fwdarw.9:1).
An analytical sample was obtained by recrystallization from isopropyl alcohol.
______________________________________Physical properties of Compound U3______________________________________Melting point 146-147.degree. C.Elementary analysis C H N______________________________________Calculated (%) 47.37 5.30 12.28(for C.sub.9 H.sub.12 N.sub.2 O.sub.5)Found (%) 47.18 5.26 12.38Specific rotations[.alpha.].sub.D.sup.20 = +97.7.degree. (c = 1.14, DMF)UV Spectrum .lambda..sub.max.sup.MeOH 263 nm (.epsilon. 10,300)IR Spectrum (KBr) cm.sup.-13430, 3270, 2960, 1620, 1452,1436, 1407, 1278, 1197, 1122,1065, 1032, 992, 921, 877, 810, 753, 718, 695, 633, 572, 540.sup.1 H-NMR spectrum (DMSO-d.sub.6) .delta.11.78(1H, br s, H-3) 4.33(1H, m, H-2')7.74(1H, d, H-6) 4.00(1H, m, H-4')5.87(1H, d, H-1') 3.60(1H, dd, H-5')5.55(1H, dd, H-5) 3.55(1H, dd, H-5")5.35(1H, br s, OH-2) 2.24(1H, m, H-3')5.05(1H, br s, OH-5') 1.75(1H, m, H-3")______________________________________
Example 23
Synthesis of 9-(3-deoxy-.beta.-D-threo-pentofuranosyl) guanine (Compound G3)
Guanosine (5.0 g, 17.7 mmol) was suspended in dry pyridine (50 ml). To the suspension was added pivaloyl chloride (9.8 ml) 79.6 mmol) under ice cooling, and the mixture was then stirred at room temperature for 45 minutes. After ice cooling, methanesulfonyl chloride (4.1 ml, 53.0 mmol) was added dropwise to the reaction mixture, after which it was first stirred at 0.degree. C. for 1 hour and then at room temperature for 3 hours. The reaction mixture was cooled with iced water and a small amount of water was added thereto and the mixture was stirred for 30 minutes. The reaction mixture was extracted with chloroform-ether and the organic layer was washed with saturated aqueous sodium bicarbonate and then with water, and dried over magnesium sulfate. The drying agent was removed by filtration and the filtrate was evaporated. The residue was dissolved in toluene and the solvent was evaporated under reduced pressure. This procedure was repeated several times to completely remove the remaining pyridine.. The residue was dissolved in methanol (120 ml). Sodium methoxide (7.6 g, 140.7 mmol) and sodium borohydride (2.7 g, 71.4 mmol) were added to the solution, after which it was first stirred at room temperature for 1 hour and then at 50.degree. C. for 5 hours. After ice cooling, a small amount of acetone was added to decompose an excess of NaBH.sub.4. Methanol (100 ml) was added to the mixture, after which it was concentrated to 1/2 volume. This procedure was repeated to remove methyl borate thus produced as a by-product. The reaction mixture was again cooled with ice, and concentrated hydrochloric acid was gradually added to neutralize. Then, water was added and the mixture was concentrated under reduced pressure. The residue from which alcohol had been removed completely was suspended in water (about 150 ml), and applied to HP-20 (DIAION: 600 ml made up with water, Mitsubishi Chemical Industries Ltd.) column. Water (about 1.5 l) was passed through the column to elute inorganic salts, and the product was then eluted with 5% methanol-water followed with 5% methanol--0.1M ammonia water. Fractions containing compound G3 were concentrated to dryness under reduced pressure and the-residue was recrystallized from methanol to give colorless crystals (1.31 g, 27.8%). The mother liquor was dried up under reduced pressure, again subjected to HP-20 column chromatography (300 ml) and followed by the same procedures mentioned above to give compound G3 (0.55 g, 11.6%).
Total amount of the obtained products was 1.86 g (39%).
______________________________________Physical properties of compound G3______________________________________Melting point > 265.degree. C. (235.degree. C. sintered)Elementary analysis C H N______________________________________Calculated (%) 44.05 5.03 25.69(for C.sub.9 H.sub.12 N.sub.2 O.sub.5)Found (%) 43.86 4.85 25.49Specific rotations[.alpha.].sub.D.sup.20 = +8.7.degree. (c = 1.10, DMF)UV Spectrum .lambda..sub.max.sup.MeOH 253 nm (.epsilon. 14,800)IR Spectrum (KBr) cm.sup.-13450, 3190, 2950, 2760, 1055,1642, 1605, 1539, 1648, 1406,1391, 1362, 1327, 1177, 1069,1045, 782, 685, 640.sup.1 H-NMR spectrum (DMSO-d.sub.6) .delta.10.82(1H, br s, NH-1) 4.42(1H, m, H-2')7.83(1H, s, H-8) 4.03(1H, m, H-4')6.64(2H, s, NH.sub.2 -2) 3.61(1H, m, H-5')5.86(1H, d, H-1') 3.54(1H, m, H-3')5.39(1H, br d, OH-2') 2.28(1H, m, H-3')5.06(1H, br t, OH-5') 1.96(1H, m, H-3")______________________________________
Example 24
Synthesis of 9-(3-deoxy-.beta.-D-threo-pentofuranosyl) adenine (Compound A'3)
Adenosine (5.0 g, 18.7 mmol) was suspended in dry pyridine (50 ml) and colled to -15.degree. C. To the suspension was added pivaloyl chloride (7.0 ml, 56.8 mmol), and the mixture was first stirred at -15.degree. C. for 1.5 hour, and then at 0.degree. C. for 2 hours. Methanesulfonyl chloride (4.3 ml, 55.6 mmol) was added dropwise to the reaction mixture under ice cooling. The mixture was stirred at room temperature for 3 hours, then cooled with ice again. A small amount of water was added and stirred for 30 minutes. The reaction mixture was extracted with chloroform-ether. The organic layer was washed with saturated aqueous sodium bicarbonate solution and then with water, and dried over magnesium sulfate. The drying agent was removed by filtration and the filtrate was concentrated in vacuo to dryness to give amorphous substances. The remaining pyridine was removed by repeated co-evaporation with toluene. The residue was dissolved in methanol (150 ml), cooled to -15.degree. C., after which sodium methoxide (8.1 g, 150 mmol) and sodium borohydride (2.5 g, 66.1 mmol) were added. The mixture was first stirred at room temperature for 14 hours and then at 50.degree. C. for 3 hours. After ice cooling, a small amount of acetone was added to the reaction mixture to decompose an excess of NaBH.sub.4. Concentrated hydrochloric acid was gradually added to neutralize the solution. Ethanol was added to the mixture, which was then concentrated under reduced pressure to remove water completely. The residue was suspended in chloroform-methanol and applied to a silica gel column (250 g). Elution with chloroform-methanol (8:1.fwdarw.5:1) gave compound A'3 as oils, which were then crystallized from ethanol-ether. Yield: 2.7 g (57%).
The physical properties of the product was identical with those reported earlier [R. Mengel and H. Wiedner, Chem. Ber., 109, 1395 (1976); A. Nilass and J. Chattopadhyaya, Synthesis, 1986, 196)].
______________________________________Physical properties of compound A'3______________________________________Melting point 190-192.degree. C.Elementary analysis C H N______________________________________Calculated (%) 47.47 5.26 27.68(for C.sub.10 H.sub.13 N.sub.5 O.sub.3.0.1H.sub.2 O)Found (%) 47.36 5.22 27.67Specific rotations[.alpha.].sub.D.sup.20 = -24.3.degree. (c = 1.08, DMF)UV Spectrum .lambda..sub.max.sup.MeOH 259 nm (.epsilon. 14,200)IR Spectrum (KBr) cm.sup.-13370, 3230, 1680, 1672, 1611,1575, 1490, 1428, 1385, 1341,1316, 1220, 1115, 1105, 1093,1056, 999, 799, 721, 652, 590.sup.1 H-NMR spectrum (DMSO-d.sub.6) .delta.8.30(1H, S, H-8) 4.51(1H, m, H-2')8.14(1H, s, H-2) 4.09(1H, m, H-4')7.24(2H, bs, NH.sub.2) 3.66(1H, m, H-5')6.15(1H, d, H-1') 3.58(1H, m, H-5")5.42(1H, d, OH-2') 2.29(1H, M, H-3')5.17(1H, t, OH-5') 2.02(1H, m, H-3")______________________________________
Industrial Utility
The dideoxynucleoside derivatives among the novel nucleoside derivatives of the present invention are useful as an antiviral agent.
Those except for the dideoxynucleoside derivatives among the novel nucleoside derivatives of the present invention are useful as intermediates for synthesizing the dideoxynucleosides derivatives.
Further, according to the synthetic processes of the present invention, above-mentioned and known intermediates can be synthesized short-step reactions using inexpensive reagents.

Number	Date	Country	Kind
62-100903	Apr 1987	JPX
62-172721	Jul 1987	JPX

Number	Date	Country
43-11458	Jan 1968	JPX
61-280500	Jan 1986	JPX

Process for preparing 3-deoxy-B-D-threo-pentofuranosyl nucleosides

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