Patent Application
20200392145
The present invention provides a process for the production of morphinan alkaloids. In particular, the invention provides an improved process for the production of morphinan alkaloids substituted at N-17 with a group other than methyl.
The point of attachment of a moiety or substituent is represented by “-”. For example, —OH is attached through the oxygen atom.
“Alkyl” refers to a straight-chain or branched saturated hydrocarbon group. In certain embodiments, the alkyl group may have from 1-20 carbon atoms, in certain embodiments from 1-15 carbon atoms, in certain embodiments, 1-8 carbon atoms. The alkyl group may be unsubstituted. Alternatively, the alkyl group may be substituted. Unless otherwise specified, the alkyl group may be attached at any suitable carbon atom and, if substituted, may be substituted at any suitable atom. Typical alkyl groups include but are not limited to methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, tert-butyl, n-pentyl, n-hexyl, and the like.
The term “cycloalkyl” is used to denote a saturated carbocyclic hydrocarbon radical. The cycloalkyl group may have a single ring or multiple condensed rings. In certain embodiments, the cycloalkyl group may have from 3-15 carbon atoms, in certain embodiments, from 3-10 carbon atoms, in certain embodiments, from 3-8 carbon atoms. The cycloalkyl group may be unsubstituted. Alternatively, the cycloalkyl group may be substituted. Unless other specified, the cycloalkyl group may be attached at any suitable carbon atom and, if substituted, may be substituted at any suitable atom. Typical cycloalkyl groups include but are not limited to cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and the like.
“Aryl” refers to an aromatic carbocyclic group. The aryl group may have a single ring or multiple condensed rings. In certain embodiments, the aryl group can have from 6-20 carbon atoms, in certain embodiments from 6-15 carbon atoms, in certain embodiments, 6-12 carbon atoms. The aryl group may be unsubstituted or substituted. Unless otherwise specified, the aryl group may be attached at any suitable carbon atom and, if substituted, may be substituted at any suitable atom. Examples of aryl groups include, but are not limited to, phenyl, naphthyl, anthracenyl and the like.
“Arylalkyl” refers to an optionally substituted group of the formula aryl-alkyl-, where aryl and alkyl are as defined above.
“Halo” or “halogen” refers to —F, —C, —Br and —I e.g. —Cl, —Br and —I.
“Morphinan” refers to a compound comprising the core structure:
“Substituted” refers to a group in which one or more (e.g. 1, 2, 3, 4 or 5) hydrogen atoms are each independently replaced with substituents which may be the same or different. The substituent may be any group which tolerates the alkylation reaction conditions. Examples of substituents include but are not limited to —Ra, —O—Ra, —S—Ra, —NRaRb and —NHRa; wherein Ra and Rb are independently selected from the groups consisting of alkyl, cycloalkyl, aryl and arylalkyl. Ra and Rb may be unsubstituted or further substituted as defined herein.
The present invention provides a process for the preparation of a compound of formula (2):
the process comprising reacting a compound of formula (1), a base and an alkylating agent R4—X in a nitrile-containing polar aprotic solvent to form the compound of formula (2), wherein the process is carried out at a temperature greater than 60° C.; and
wherein:
R1 and R2 are independently selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group;
R3 is —C(R10)(R11)(OH) or a protected —C(═O)(R12);
R4 is selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl, unsubstituted —C1-20-alkyl-C3-20-cycloalkyl, substituted —C1-20-alkyl-C3-20-cycloalkyl, unsubstituted allyl and substituted allyl;
R10, R11 and R12 are independently selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl and substituted cyclic C3-C20-alkyl;is a double bond or a single bond; and
X is a halo group.
The compounds described herein may have chiral centres at positions C-5, C-6, C-7, C-9, C-13 and C-14 of the morphinan structure. The ethano/ethano bridge between carbon atoms C-6 and C-14 is either on the alpha or beta face of the compound. The compounds of formulae (1) and (2) may have the stereochemistry shown below:
When R1 and/or R2 are H, the hydroxy groups present at C-3- and/or C-6 may be susceptible to alkylation. Thus, it is may be desirable to first protect one or both of the hydroxy groups with a suitable protecting group which may be optionally removed after the alkylation is completed. Protecting groups are known in the art and methods for their introduction and removal are described in standard references such as “Greene's Protective Groups in Organic Synthesis”, P. G. M. Wuts and T. W. Greene, 4th Edition, Wiley.
R1 is selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group. R1 may be selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. R1 may be selected from the group consisting of —H and an unsubstituted straight-chain C1-C20-alkyl, such as —H or -Me. In one embodiment, R1 may be —H. In another embodiment, R1 may be -Me.
R2 is selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group. R2 may be selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. R2 may be selected from the group consisting of —H and an unsubstituted straight-chain C1-C20-alkyl, such as —H or -Me. In one embodiment, R2 may be —H. In another embodiment, R2 may be -Me.
One of R1 and R2 may be selected from the group —H and the other of R1 and R2 may be an unsubstituted straight-chain C1-C20-alkyl. For example, one of R1 and R2 may be —H and the other of R1 and R2 may be -Me. R1 may be —H or -Me and R2 may be -Me.
R3 may be —C(R10)(R11)(OH), wherein R10 and R11 are independently selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl and substituted cyclic C3-C20-alkyl.
R10 may be selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. For example, R10 may be selected from a butyl (i-, p- or b-) and a methyl group. R10 may be a tert-butyl or methyl group.
R11 may be selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. For example, R11 may be selected from a propyl (n- or i-), butyl (n-, i-, p- or t-) or a methyl group. R11 may be a n-propyl, tert-butyl or methyl group.
In one embodiment, R3 is
In another embodiment, R3 is
In another embodiment, R3 is
R3 may be a protected —C(═O)(R12). It is may be desirable to first protect the keto group with a suitable protecting group which may be optionally removed after the alkylation step is completed. Protecting groups are known in the art and methods for their introduction and removal are described in standard references such as “Greene's Protective Groups in Organic Synthesis”, P. G. M. Wuts and T. W. Greene, 4th Edition, Wiley. Suitable keto protecting groups include but are not limited to acetals and ketals. For example, substituted or unsubstituted, straight-chain or branched C1-C20-alkanols, substituted or unsubstituted, straight-chain or branched 1,2-(C1-C20)-alkyl-diols (for example, ethylene glycol or 1,2-propanediol), or substituted or unsubstituted, straight-chain or branched 1,3-(C1-C20)-alkyldiols may be conveniently utilised to form suitable acetals or ketals. A diol reacts to form a ring and in this instance, the ketal comprises substituted or unsubstituted chiral or achiral bridges which are derived, for example, from the skeletons —(CH2)n— (n=2, 3 or 4), —CH(CH3)CH(CH3)—, —CH(CH3)CH2CH(CH3)—, —CMe2-, —CHMe-, no limitation being implied by this listing. The protecting group may be removed by methods known in the art to form C(═O)(R12).
R12 may be selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. For example, R12 may be a methyl group.
is a double bond or a single bond. In one embodiment,
is a —C═C— double bond. In another embodiment,
is a —C—C— single bond.
The compound of formula (1) may be:
The compound of formula (2) may be:
The base may be an organic base or an inorganic base. When the base is an organic base, it may be selected from the group which includes but is not limited to amine bases, such as pyridine, triethylamine, tripropylamine, tributylamine, N,N-diisopropylamine, N-methylmorpholine, or N,N-dimethylaminopyridine.
When the base is an inorganic base, it may be selected from the group which includes but is not limited to borates, phosphates, acetates, carbonates and bicarbonates (i.e. hydrogen carbonates). Suitable borates include alkali metal borates (e.g. lithium borate, sodium borate or potassium borate). Suitable phosphates include alkali metal phosphates (e.g. lithium phosphate, sodium phosphate or potassium phosphate). Suitable acetates include alkali metal acetates (e.g. lithium acetate, sodium acetate or potassium acetate). Suitable carbonates include but are not limited to alkali metal carbonates (e.g. lithium carbonate, sodium carbonate or potassium carbonate) and alkaline earth metal carbonates (e.g. calcium carbonate). Suitable bicarbonates include but are not limited to alkali metal bicarbonates (e.g. lithium bicarbonate, sodium bicarbonate or potassium bicarbonate).
Strong bases, for example, hydroxides or alkoxides, may be used in the process of the present invention provided that hydroxy groups present at C-3 and/or C-6 of the compound of formula (1) (i.e. when R1 and R2 are —H) are protected beforehand with a suitable alcohol-protecting group. Examples of hydroxides include alkali metal hydroxides (e.g. lithium hydroxide, sodium hydroxide or potassium hydroxide) or tetraalkylammonium hydroxides. Examples of alkoxides include alkali metal alkoxides (e.g. lithium alkoxide, sodium alkoxide or potassium alkoxide) or tetraalkylammonium alkoxides.
The molar ratio of the compound (1):base may be from about 1:1 to about 1:2.0. In some embodiments, the molar ratio of the compound (1):base may be about 1:1. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.1. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.2. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.3. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.4. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.5. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.6. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.7. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.8. In some embodiments, the molar ratio of the compound (1):base may be about 1:1.9. In some embodiments, the molar ratio of the compound (1):base may be about 1:2.0.
The polar aprotic solvent has a nitrile (—C═N) group. The nitrile-containing aprotic solvent may have a boiling point at atmospheric pressure (i.e. 1.0135×105 Pa) greater than 60° C. and below 250° C. The nitrile-containing aprotic solvent may be acetonitrile, propionitrile or butyronitrile. In one embodiment, nitrile-containing aprotic solvent is acetonitrile. It is desirable that the solvent is selected such that either compound (1) or compound (2) is partially soluble in the solvent i.e. the compound (1) or (2) is partially present as solid as well as being partially dissolved in the solvent. In this instance, the other of compound (1) or (2) is desirably substantially soluble in the solvent. For example, the compound (1) may be partially soluble in the solvent whereas the product, compound (2), may be substantially soluble in the solvent. Alternatively, the compound (1) may be substantially soluble in the solvent whereas the product, compound (2), may be partially soluble in the solvent. Without wishing to be bound by theory, it is believed that this difference in solubilities between starting material and product helps drive the alkylation reaction towards completion.
The ratio of compound (1):polar aprotic solvent may be in the range of about 0.01:0.5 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.01 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.02 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.03 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.04 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.05 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.06 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.07 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.5 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.45 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.40 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.35 g/mL. In some embodiments, the ratio of compound (1):solvent may be about 0.20 g/mL. In some embodiments, the ratio of compound (1) solvent may be about 0.15 g/mL. In some embodiments, the ratio of compound (1) solvent may be about 0.10 g/mL. In some embodiments, the ratio of compound (1):solvent may be in the range of about 0.01 to 0.2 g/mL, such as about 0.06 to 0.10 g/mL, for example, about 0.08 g/mL.
The compound of formula (1), the base and the alkylating agent R4—X are heated in the polar aprotic solvent to an internal temperature greater than 60° C. The temperature may be greater than 60° C. and up to the boiling point of the reaction mixture. The boiling point of the reaction mixture may vary depending on the pressure under which the alkylation reaction is conducted. The temperature may be in the range of >60° C. to about ≤250° C. In some embodiments, the temperature may be about ≥61° C. In some embodiments, the temperature may be about ≤62° C. In some embodiments, the temperature may be about ≥63° C. In some embodiments, the temperature may be about ≥64° C. In some embodiments, the temperature may be about ≤250° C. In some embodiments, the temperature may be about ≤240° C. In some embodiments, the temperature may be about ≤230° C. In some embodiments, the temperature may be about ≤220° C. In some embodiments, the temperature may be about ≤210° C. In some embodiments, the temperature may be about ≤200° C. In some embodiments, the temperature may be about ≤190° C. In some embodiments, the temperature may be about ≤180° C. In some embodiments, the temperature may be about ≤170° C. In some embodiments, the temperature may be about ≤160° C. In some embodiments, the temperature may be about ≤150° C. In some embodiments, the temperature may be about ≤140° C. In some embodiments, the temperature may be about ≤130° C. In some embodiments, the temperature may be about ≤120° C. In some embodiments, the temperature may be about ≤110° C. In some embodiments, the temperature may be about ≤100° C. In some embodiments, the temperature may be about ≤90° C. In some embodiments, the temperature may be about ≤80° C. In some embodiments, the temperature may be about ≤70° C. In some embodiments, the temperature may be in the range of about ≥60° C. to ≤70° C., such as about ≥63° C. to ≤67° C., such as about 65° C.
Without wishing to be bound by theory, it is believed that the nitrogen lone pair of 17N-H acts as a nucleophile and reacts with the alkylating agent R4—X to form a quaternary group. The quaternary group is then deprotonated with the base to form the compound (2).
R4 is selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl, unsubstituted —C1-20-alkyl-C3-20-cycloalkyl, substituted —C1-20-alkyl-C3-20-cycloalkyl, unsubstituted allyl and substituted allyl. R4 may be selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, unsubstituted —C1-20-alkyl-C3-20-cycloalkyl, and unsubstituted allyl. For example, R4 may be a cyclopropylmethyl
cyclobutylmethyl
or allyl group
In one embodiment, R4 is a cyclopropylmethyl group.
X is a halo group which may be selected from —Cl, Br— or —I.
The molar ratio of the compound (1):R4—X may be from about 1:1 to about 1:2.0. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.1. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.2. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.3. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.4. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.5. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.6. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.7. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.8. In some embodiments, the molar ratio of the compound (1) R4—X may be about 1:1.9. In some embodiments, the molar ratio of the compound (1):R4—X may be about 1:2.0.
The alkylating agent R4—X may be added to the compound (1) and the base in the polar aprotic solvent before the internal temperature of the reaction has reached >60° C. In this instance, the alkylating agent R4—X may be added at the start of the process when the compound (1), base, and alkylating agent R4—X are combined in the solvent. Alternatively, the compound (1), base and solvent may be heated to temperature (i.e. >60° C.) and the alkylating agent R4—X added once the reaction mixture is at the desired temperature. The alkylating agent R4—X may be added at a consistent rate (e.g. over a 30 minute time period or more) to control the alkylation at the 17N position. When R1 is —H, a consistent addition rate also minimizes over alkylation at phenol group at C-3.
When X is —Br or —Cl, the process may further comprise an alkali metal iodide (e.g. sodium iodide or potassium iodide). Without wishing to be bound by theory, R4—Cl or R4—Br may undergo a halide exchange with the alkali metal iodide to form the corresponding R4—I in situ. The initial reaction mixture therefore may comprise the compound (1), the base, the solvent, the alkali metal iodide, and either R4—Cl or R4—Br. The alkali metal iodide may be present in sub-stoichiometric, stoichiometric or greater than stoichiometric molar ratios as compared to the compound (1). The molar ratio of the compound (1):alkali metal iodide may be from about 1:1 to about 1:2.0. In some embodiments, the molar ratio of the compound (1) alkali metal iodide may be about 1:1. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.1. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.2. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.3. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.4. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.5. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.6. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.7. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.8. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:1.9. In some embodiments, the molar ratio of the compound (1):alkali metal iodide may be about 1:2.0.
Examples of R4—X include but are not limited to cyclopropylmethyl chloride, cyclopropylmethyl bromide, cyclopropylmethyl iodide, cyclobutylmethyl chloride, cyclobutylmethyl bromide, cyclobutylmethyl iodide, allyl chloride, allyl bromide and allyl iodide.
The process may be carried out under an inert atmosphere, such as under nitrogen or argon gas.
The process is carried out for a period of time until it is determined that the process is complete. Completion of the process may be determined by in-process analysis or other suitable method. Typically, the process is complete within about 24 hours.
On completion, the reaction vessel and its contents may be cooled to ambient temperature and the solvent removed (for example, by distillation or stripping methods).
In another aspect, the present invention provides a process for the preparation of a compound of formula (4):
the process comprising reacting a compound of formula (3), a base and an alkylating agent R4—X in a nitrile-containing polar aprotic solvent to form the compound of formula (4), wherein the process is carried out at a temperature greater than 60° C.; and
wherein:
group;
R20 and R21 are independently selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group;
R4 is selected from the group consisting of an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl, unsubstituted C1-20-alkyl-C3-20-cycloalkyl, substituted C1-20-alkyl-C3-20-cycloalkyl, unsubstituted allyl and substituted allyl; is a double bond or a single bond; and
X is a halo group.
The alkylation conditions, base, alkylating agent R4—X, nitrile-containing polar aprotic solvent, temperature, , alkali metal iodide (if any), molar ratio of starting material:base, molar ratio of starting material:R4—X, molar ratio of starting material:alkali metal iodide as described above for the first aspect of the invention generally likewise apply to this aspect of the invention.
The compounds described herein may have chiral centres at positions C-5, C-9, C-13 and C-14 of the morphinan structure. The compounds of formulae (3) and (4) may have the stereochemistry shown below:
R20 is selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group. R20 may be selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. R20 may be selected from the group consisting of —H and an unsubstituted straight-chain C1-C20-alkyl, such as —H or -Me. In one embodiment, R20 may be —H. In another embodiment, R20 may be -Me.
R21 is selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, substituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, substituted branched-chain C1-C20-alkyl, unsubstituted cyclic C3-C20-alkyl, substituted cyclic C3-C20-alkyl and alcohol protecting group. R21 may be selected from the group consisting of —H, an unsubstituted straight-chain C1-C20-alkyl, unsubstituted branched-chain C1-C20-alkyl, and unsubstituted cyclic C3-C20-alkyl. R21 may be selected from the group consisting of —H and an unsubstituted straight-chain C1-C20-alkyl, such as —H or -Me. In one embodiment, R21 may be —H. In another embodiment, R21 may be -Me.
Y may be a
group, which forms a carbonyl group with the carbon atom at C-6. Alternatively, Y can be a
group, which forms an alkenyl group with the carbon atom at C-6.
The compound of formula (3) may be:
The compounds of formula (4) may be:
Compounds (4) comprising
as the Y group may be transformed into the
group by methods known in the art. For example, nalmefene may be prepared from naltrexone using methylenetriphenylphosphorane (Hahn et al, J. Med. Chem., 18, 259 (1975)).
Embodiments and/or optional features of the invention have been described above. Any aspect of the invention may be combined with any other aspect of the invention, unless the context demands otherwise. Any of the embodiments or optional features of any aspect may be combined, singly or in combination, with any aspect of the invention, unless the context demands otherwise.
The invention will now be described by way of the following non-limiting Example:
The process is carried out under a nitrogen atmosphere.
Nordiprenorphine (1.3 g) is charged to a reaction vessel. Potassium bicarbonate (0.524 g), potassium iodide (0.87 g) and acetonitrile (15.6 mL) are added. The reaction mixture is heated to 65° C. while stirring. Cyclopropane methyl bromide (0.474 mL) is added slowly with a consistent addition rate over a 30 minute time period. Heating at 65° C. is continued for 13.5 hours. Stirring is stopped and the sediment is allowed to settle.
The suspension is allowed to cool to ambient temperature and transferred to a rotary evaporator flask. Acetonitrile may be used to aid the transfer. The suspension is concentrated to dryness using the rotary evaporator.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1719667.6 | Nov 2017 | GB | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/GB2018/050137 | 1/18/2018 | WO | 00 |
