Triazolo-epothilones

Abstract

The invention relates to triazolo-thiazole analogues of epothilone A and epothilone B.

Description

The invention relates to triazolo-thiazole analogues of epothilone A and epothilone B.

Epothilones are macrocyclic lactones having a fungicidal and cytotoxic effect. There is a continuous need for analogues or derivatives having comparable or better activity, which can be used as fungicides or cytostatic agents.

An overview of the chemistry of epothilones is given, for example, by Nicolaou et al. in Angew. Chem. Int. Ed. 1998, Vol. 37, 2014-2045.

The problem of the invention is to provide epothilone analogues or derivatives of that kind.

The invention accordingly relates to triazolo-thiazole analogues of epothilone A and epothilone B of formula 4a or 4b:

wherein:

R denotes H, CH₃

Z denotes H, alkyl, aryl, heteroaryl.

The triazolo-thiazole epothilones according to the invention are very effective fungicides and highly potent cytostatic agents having favourable pharmacological properties.

Alkyl denotes straight-chain or branched C₁-C₆alkyl which may be (mono- or poly-)substituted as desired, for example methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl and hexyl. Examples of substituents are C₁-C₆alkoxy, C₁-C₆acyl, hydroxyl and halogen such as bromine, chlorine, fluorine and iodine.

Aryl denotes mononuclear or polynuclear aromatic systems which may be (mono- or poly-)substituted as desired, for example phenyl, o-, m-, p-tolyl, o-, m-, p-xylyl, benzyl, phenethyl and naphthyl. Examples of substituents are C₁-C₆alkyl, C₁-C₆alkoxy, C₁-C₆acyl, hydroxyl and halogen such as bromine, chlorine, fluorine and iodine.

Heteroaryl denotes mononuclear or polynuclear heteroaromatic systems which may be (mono- or poly-)substituted as desired, it being possible for the aromatic nucleus to have one or more hetero atoms selected from N, O and S. Examples of heteroaryl are furyl, pyranyl, pyrrolyl, imidazolyl, pyrazolyl, pyridyl and indolyl. Examples of substituents are C₁-C₆alkyl, C₁-C₆alkoxy, C₁-C₆acyl, hydroxyl and halogen such as bromine, chlorine, fluorine and iodine.

The invention relates also to a method of preparing the triazolo-thiazole analogues of epothilone A and epothilone B according to the invention and to fungicidal and pharmaceutical compositions comprising one or more such analogues, and to the use of the analogues and of the fungicidal or pharmaceutical compositions comprising them for combating fungi or for treating diseases that can be treated with cytostatic agents, for example tumour diseases such as cancer or disorders of cell growth.

The fungicidal and pharmaceutical compositions may comprise, besides the actual active ingredient, conventional carriers, diluents or excipients, for example stabilisers such as UV absorbers, anti-oxidants and preservatives.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a synthesis route for preparation of the triazolo-thiazole analogues of epothilone A and epothilone B according to the invention.

FIG. 2 is a synthesis route for preparation of the diazo from the triazolo form according to the invention.

FIG. 3 is a another synthesis route for preparation of the analogues of the present invention.

FIG. 1 shows a synthesis route for preparation of the triazolo-thiazole analogues of epothilone A and epothilone B according to the invention.

The preparation of the triazolo-thiazole analogues of epothilone A and epothilone B according. to the invention is described hereinbelow, without limitation, with reference to FIG. 1. The abbreviation Met denotes metal.

The preparation of C21-modified epothilones, that is to say the aldehydes, ketones and hydrazones of formulae 1, 2 and 3, respectively, is described in the published German Patent Application DE 199 07 588 and in the published International Patent Application WO 2000/050423 of the Applicant. In the method according to the invention, oxidative ring closure is performed on the hydrazone derivatives of formulae 3a and 3b with the aid of metal oxides, preferably NiO₂, K₃[Fe(CN)₆], lead tetraacetate or sodium hypochloride (cf. Houben-Weyl, Vol. E 14b, 4th Edition, 1999).

Synthesis of a Triazolo-thiazole Analogue of Epothilone A (Formula 4a, Z=H):

24.6 mg (47.2 μmol) of epothilone-A-21-aldehyde hydrazone (formula 3a) are dissolved in 1.5 ml of absolute dichloromethane. Three aliquots, each of 42.8 mg (472.2 μmol), of nickel peroxide are added at 15-minute intervals, with stirring at room temperature. The mixture is then filtered over Celite, rinsing with dichloromethane. The combined organic phases are concentrated and are dried in a high vacuum. The crude product is purified by means of preparative HPLC (mobile phase: acetonitrile/water 38:62; column: Nucleosil 100 C18 7 μm, 21×250 mm). 12.0 mg (49%) of product were obtained.

The spectroscopic data are identical to epothilone A (cf. DE 4138042 C2) with the exception of:

¹H NMR (400 MHz, CDCl₃): d=2.25 (dt, 2a-H), 2.57 (dd, 2b-H), 4.63 (m, 3-H), 5.02 (dd, 3-OH), 1.68 (m, 14a-H), 2.31 (dt, 14b-H), 5.53 (d, 15-H), 6.92 (bs, 17-H), 7.06 (s, 19-H), 7.84 (s, 21-H), 1.08 (s, 22-H), 1.55 (s, 23-H); ¹³C NMR (100 MHz, CDCl₃): d=73.0 (3-C), 54.7 (4-C), 41.4 (6-C), 71.4 (7-C), 32.0 (14-C), 74.9 (15-C), 145.1 (16-C), 109.2 (17-C), 129.2 (18-C), 115.5 (19-C), 136.4 (20-C), 124.8 (21-C), 15.9 (C-22), 23.3 (23-C), 12.7 (24-C), 18.1 (27-C); HRMS (DCI): C₂₆H₃₇N₃O₆S: [M+NH₄+] calculated 537.2747, found 537.2721.

Synthesis of a triazolo-thiazole analogue of epothilone B (Formula 4b, Z=H):

8.1 mg (15.1 μmol) of epothilone-B-21-aldehyde hydrazone (formula 3b) are dissolved in 1 ml of absolute dichloromethane. 13.7 mg (151.4 μmol) of nickel peroxide are added to the solution, whereupon stirring is carried out at room temperature for 15 minutes. The nickel peroxide is filtered off over Celite, washing with dichloromethane. The combined organic phases are concentrated and are dried in a high vacuum. The crude product is purified by means of preparative HPLC (mobile phase: acetonitrile/water 40:60; column: Nucleosil 100 C18 7 μm, 21×250 mm), yielding 4.7 mg (58%) of product.

The spectroscopic data are identical to epothilone B (cf. DE 4138042 C2) with the exception of:

¹H NMR (400 MHz, CDCl₃): d=2.25 (dt, 2a-H), 2.59 (dd, 2b-H), 4.69 (m, 3-H), 5.02 (dd, 3-OH), 1.76 (m, 14a-H), 2.31 (dt, 14b-H), 5.53 (d, 15-H), 6.91 (bs, 17-H), 7.06 (s, 19-H), 7.85 (s, 21-H), 1.08 (s, 22-H), 1.56 (s, 23-H); ¹³C NMR (100 MHz, CDCl₃): d=71.3 (3-C), 54.9 (4-C), 41.0 (6-C), 72.4 (7-C), 33.1 (14-C), 75.2 (15-C), 145.3 (16-C), 108.9 (17-C), 129.2 (18-C), 115.5 (19-C), 136.5 (20-C), 124.9 (21-C), 15.7 (22-C), 23.2 (23-C), 12.0 (24-C), 18.1 (27-C); MS (ESI): [M+H⁺]=534.

The pharmacological activity is shown in the following Table:

Growth Test Using Mammalian Cell Cultures

	Triazolo derivative of
Cell		epothilone A
line	Origin	IC-50 [ng/ml]	epothilone B
L929	Mouse (subcutaneous fat tissue)	10	1.0
K-562	Human (leukaemia)	6	0.7
U-937	Human (lymphoma)	4	0.5

Preparation of 21-O-acetyl-epothilone E (5a, R′=CH₃):

2 μl (35.0 μmol) of glacial acetic acid are added to a solution of 3.2 mg (6.2 μmol) of triazolo-epothilone A in 250 μl of dichloromethane and stirring is carried out overnight at room temperature. Water is added to the reaction mixture and extraction with ethyl acetate is carried out three times. The combined organic phases are concentrated and are dried in a high vacuum. 2.8 mg (82%) of 21-O-acetyl-epothilone E were obtained.

The spectroscopic data are identical to epothilone A (cf. DE 4138042 C2) with the exception of:

¹H NMR (400 MHz, CDCl₃): δ=6.60 (bs, 17-H), 7.14 (s, 19-H), 5.34 (s, 21-H₂), 2,14 (s, 2′-H₃); ¹³C NMR (100 MHz, CDCl₃): 137.8 (C-16), 119.6 (C-17), 152.5 (C-18), 118.0 (C-19), 163.7 (C-20), 62.5 (C-21), 170.2 (C-1′), 20.9 (C-2′); R_f (CH₂Cl₂/MeOH 95/5): 0.45; HRMS (EI) C₂₈H₄₁NO₈S: [M]⁺ calculated 551.2553, found 551.2519

Preparation of epothilone E-21-O-3′-methoxycarbonyl)propynoic acid ester (5a, R′=CH₃OOC—C₂):

7.0 mg (55.0 μmol) of acetylenedicarboxylic acid monomethyl ester are added to a solution of 5.1 mg (9.8 μmol) of triazolo-epothilone A in 400 μl of dichloromethane. The reaction mixture is stirred overnight at room temperature, water is then added thereto, and extraction with ethyl acetate is carried out three times. The combined organic phases are concentrated and are dried in a high vacuum. After purification by means of PLC (CH₂Cl₂/methanol 95/5) 3.6 mg (59%) of epothilone E-21-O-(3′-methoxycarbonyl)propynoic acid ester were obtained.

The spectroscopic data are identical to epothilone A (cf. DE 4138042 C2) with the exception of:

¹H NMR (400 MHz, CDCl₃): δ=5.45 (dd, 15-H), 6.60 (17-H), 7.20 (s, 19-H), 5.49 (bs, 21-H₂), 3.85 (s, 5′-H₃); ¹³C NMR (100 MHz, CDCl₃): 76.5 (C-15), 138.2 (C-16), 119.5 (C-17), 153.0 (C-18), 118.8 (C-19), 161.2 (C-20), 64.2 (C-21), 151.1 (C-1′), 152.0 (C-4′), 53.6 (C-5′); R_f (CH₂Cl₂/MeOH 95/5): 0.32; MS (DCI): [M+NH₄]⁺=637.

Photolysis of triazolo-epothilone A to Form 21-O-methyl-epothilone A (5a, Nu—H═CH₃OH):

9.7 mg (18.7 μmol) of triazolo-epothilone A are dissolved in 1 ml of methanol and, with cooling (ice bath 0° C.), are exposed to light for four hours using a mercury vapour lamp (DEMA, HPK-125). The solvent is then reduced and the reaction mixture is separated by means of preparative HPLC (CH₃CN/H₂O 40/60). 2.1 mg (24%) of 21-methoxy-epothilone A were isolated.

The spectroscopic data are identical to epothilone A (cf. DE 4138042 C2) with the exception of:

¹H NMR (300 MHz, CDCl₃): δ=6.61 (bs, 17-H), 7.13 (s, 19-H), 4.71 (s, 21-H₂), 3.49 (s, 1′-H₃); ¹³C NMR (75 MHz, CDCl₃): 137.5 (C-16), 120.0 (C-17), 152.2 (C-18), 117.3 (C-19), 167.8 (C-20), 71.5 (C-21), 59.1 (C-1′); R_f (CH₂Cl₂/MeOH 95/5): 0.33; HRMS (EI): C₂₇H₄₁NO₇S: [M]⁺ calculated 523.2604, found 523.2609.

1,3-Dipolar cycloaddition of acetylenedicarboxylic acid dimethyl ester and triazolo-epothilone A to Form the pyrazole derivative 6a:

1.8 mg (3.5 μmol) of triazolo-epothilone A are dissolved in 200 μl of dichloromethane. Over a period of four hours, three aliquots, each of 4.3 μl (34.7 μmol), of acetylenedicarboxylic acid dimethyl ester are added and stirred at room temperature. The reaction mixture is concentrated slightly and separated by means of PLC (CH₂Cl₂/methanol 95/5). 2.0 mg (87%) of cycloaddition product were obtained.

The spectroscopic data are identical to epothilone A (cf. DE 4138042 C2) with the exception of:

¹H NMR (400 MHz, CDCl₃): δ=5.49 (dd, 15-H), 6.63 (bs, 17-H), 7.29 (s, 19-H), 3.97 (s, 4′-H₃), 3.95 (s, 6′-H₃); R_f (CH₂Cl₂/MeOH 95/5): 0.17; HRMS (DCI): C₃₂H₄₃N₃O₁₀S: [M+H]⁺ calculated 662.2742, found 662.2778.

Claims

1. A method of preparing triazolo-thiazole analogues of epothilone A or epothilone B of formula 4a or 4b:

2. A method according to claim 1, wherein the metal oxide is NiO2.

3. A pharmaceutical composition comprising or consisting of one or more triazolo-thiazole analogues of epothilone A or epothilone B of formula 4a or 4b: