WO2008054233A2

WO2008054233A2 - Process for the preparation of docetaxel

Info

Publication number: WO2008054233A2
Application number: PCT/PL2007/000073
Authority: WO
Inventors: Osman Achmatowicz; Krzysztof Bankowski; Wieslaw Szelejewski; Olga Michalak; Barbara Szechner
Original assignee: Instytut Farmaceutyczny
Priority date: 2006-10-31
Filing date: 2007-10-31
Publication date: 2008-05-08
Also published as: WO2008054233A3; PL380970A1; PL210984B1

Abstract

The process for preparation of docetaxel consists in that the hydroxyl groups at C-7 and C-IO position of 10- deacetylbaccatin III and the amino group of (4S,5R)-2- methoxyphenyl-4-phenyl-l, 3-oxazolidine-5-carboxylic acid are protected with allyloxycarbonyl to give 7,10- diallyloxycarbonyoxyl-10-deacetylbaccatin III (VI) and (4S, 5R)-N- allyloxycarbonyl-2- (4-methoxyphenyl) -4-phenyloxazolidine-5- carboxylic acid (IV), respectively, said groups after esterif ication are removed in one technological operation, whereas the synthesis is finalized by the introduction of a tert-butyloxycarbonyl group onto the amino group of (2R, 3S) -3-phenylisoserine sida chain.

Description

Process for the preparation of docetaxel The invention relates to the process for preparation of docetaxel. The invention also relates to the new intermediates isolated in the process for the preparation of docetaxel.

Docetaxel (Taxotere^®), (2R,3S)-3-tert- butyloxycarbonylamino-2-hydroxy-3-phenylpropanoic acid 4- acethoxy-2α-benzoyloxy-5β ,20-epoxy- 1 ,7β 1 Oβ-trihydroxy-9-oxo- tax-l l-en-13α-yl ester, is the cytostatic semi- synthetic derivative of taxane.

Chemical structure of docetaxel and paclitaxel (Taxol®), both belonging to the taxane cytostatics, is shown in Fig. 1.

docetaxel Ri = (CH₃J₃OCO R₂ = H paclitaxel Ri = C₆H₅CO R₂ = COCH₃ Fig.l

Both docetaxel and paclitaxel are esters of iV-substituted (2i?,3S)~3-phenylisoserine with a hydroxy group at C13 carbon in 10-deacetylbaccatin III (docetaxel) or in baccatin III (paclitaxel).

Docetaxel and the process for its preparation is described in the European Patent EP 253958 Bl. The main synthetic methods for docetaxel preparation include selective protecting of hydroxyl groups (at carbon atoms C-7 and C-IO) and esterification of such protected 10- deacetylbaccatin with the use of a derivative of (2R,3S)-3- phenylisoserine with protected hydroxyl group functionalized at nitrogen atom. After the esterification, protecting groups are removed and the product is purified.

The above mentioned methodology has numerous detailed embodiments due to the possibility of using various protecting groups, both for 10-deacetylbaccatin III and for (2R,3Sj- phenylisoserine molecules.

For example, as protecting groups of hydroxyl at carbon atom C-7 in baccatin III (paclitaxel synthesis) or both hydroxyl groups C-7 and C-10 in 10-deacetylbaccatin III (docetaxel synthesis), inter alia triethylsilyl [US 4,814,470, US 4,924,011, Denis J. et al., J. Am. Chem. Soc, 1988, 110, 5917], 2,2,2- trichloroethoxycarbonyl (Troc) [EP 0253738 Bl, US 4,814,470, US 5,476,954]; trichloroacetyl [WO 98/08832, EP 1 157 018]; ben∑yloxycarbonyl (Cbz) [US 5,688,977); chloroacetyl [US 2004/0073044], imidazolocarbonyl [WO 02/ 12216 Al] were used. In an appropriate moment of the synthesis, the protecting groups are removed under acidic or alkaline conditions, with the use of Zinc (Troc) or by catalytic hydrogenation (Cbz).

Regardless of the selection of protecting groups, the main problem is performing of the reaction of esterification. C- 13 hydroxyl group, due to the steric hindrance effect, is slightly reactive; the esterification reaction should be carried out under forcing conditions, for many hours, at high temperatures and with high excess of acylating reagent [US 4,814,470, US 4,924,011 and Denis J. et al. J. Am. Chem. Soc, 1988, 110, 5917]. Yields of the reaction are low, and moreover, it is accompanied by epimerization at C-2' hydroxyl group in phenyliso serine residue, resulting in a mixture which is hard to resolve (eg., A.M. Kanazawa et al., J. Org. Chem. 1994, 59, 1238).

This problem has been resolved by the use of the non- linear precursors of (2R,3S)-phenylserine in esterification, for example derivatives of oxazolidine-5-carboxylic acid [US 5,621, 121; US 5,637,723, EP 1157018 Al, US 2004/0073044 Al] of general formula shown in Fig.2:

Fig.2

Compounds of this type easily esterify C- 13 hydroxyl group in the protected deacylbaccatin III.

This synthetic approach requires, after esterification, cleavage of cyclic oxazolidine system with the reproduction of

(2-R,3S)-3-phenylserine system. Examples of cleavage of oxazolidine ring in the presence of Boc group, eg., with formic acid [EP 1157018 Al] or trifluoroacetic acid/ acetic acid/water mixture [US 2004/0073044 Al) are known in the art. Due to required use of acidic conditions of hydrolysis, there is a serious risk of simultaneous removal of tert-butylcarbonyl protection. For example, the publication WO 02/ 12216 teaches that in the synthesis step (iii) that during the cleavage of oxazolidine ring under acidic conditions tert-butyloxcarbonyl group is also removed.

At present, we observed that these difficulties, especially uncomfortable in the case of docetaxel synthesis at technical scale, may be avoided, due to the use of the protecting group .which, is removable at the earlier step of synthesis and the introduction of tert-butyloxycarbonyl group into the molecule at the final step of the process.

In the process according to the invention, in esterification of 10-deacetolobaccatin III with oxazolidine precursor (22?,3$)- phenylisoserine, the same protection group is used, both for hydroxy groups C7-OH and ClO-OH in the residue of 10- deacetylobaccatin III as well as for amino group in the residue of

(2i?,3.S)-3-phenylisoserine. The said group is allyloxycarbonyl

(Aoc). Allyloxycarbonyl protection, after esterification, is removed upon one technological operation, whereas the synthesis is finalized by the introduction of tert-butyloxycarbonyl group onto amino group of (2i?,3S)-3-phenylisoserine.

The process for the preparation of docetaxel according to the invention comprises:

(i) Simultaneous protection of the hydroxyl groups at C-7 and C-10 position of 10-deacetolobaccatin III and amino group of (4S,5R)-2-methoxephenyl-4- phenyl-l,3-oxazolidine-5-carboxylic acid with allyloxycarbonyl to give 7, 10-diallyloxycarbonyl- 10- deacetylbaccatin III (VI) and (4S,5i?)-iV- allyloxycarbonyl-2 - (4-metoxyphenyl) -4- phenyloxazolidine-5-carboxylic acid (IV), respectively,

(ii) Esterification of the hydroxyl group at C- 13 position in 7, 10-diallyloxycarbonyl-lO-deacetylbaccatin III (VI) with (4S,5i?)-iV-allyloxycarbonyl-2-(4- metoxyphenyl)-4-phenyloxazolidine-5-carboxylic acid (IV) in the presence of condensing agent and a base, to give 13-[N-allyloxycarbonyl-2- methoxyphenyl-4-phenyl- 1 ,3-oxazolidine-5- carboxyl]-7, 10-diallyloxycarbonyl- 10- deacetylbaccatin (VII), (iii) Simultaneous removal of allyloxycarbonyl protective groups in 13-N-allyloxycarbonyl-2-methoxypenyl-4- phenyl- 1 ,3-oxazolidine-5-carboxyl]-7, 10- diallyloxycarbonyl-10-deacetylbaccatin III (VII) to give 13-[2-methoxyphenyl-4-phenyl- 1 ,3-oxazolidine- 5-carboxyl]-10-deacetylbaccatin III (VIII),

(iv) Cleavage of the oxazolidine ring in 13-[2- methoxyphenyl-4 -phenyl- 1 ,3-oxazolidine-5- carboxyl]-10-deactylbaccatin (III) to obtain desBoc- docetaxel (IX), (v) Acylation of the amino group of desBoc-docetaxel

(IX) to obtain docetaxel (X), and (vi) Optionally, purification of docetaxel (X). The other aspect of the invention is a process for preparation of the starting compound, (4 S, 5 R)- N- allyloxycarbonyl-2-(4-methoxyphenyl)~4-phenyloxazolidine-5- carboxylic acid, which comprises: (i) protection of the amino group (2R,3S)-3~ phenylisoserine methyl ester (I) with allyloxycarbonyl, to obtain iV-allyloxycarbonyl-

methyl ester (II),

(ii) cyclization of JV-allyloxycarbonyl~(2i?,3₁S)-3- phenylisoserine methyl ester (II) to (4S,5JR)-JV- allyloxycarbonyl-2 - (4-methoxyphenyl) -4- phenyloxazolidine-5-carboxylic acid methyl ester (III),

(iii) hydrolysis of compound (III) to (4S,5R)-N- allyloxycarbonyl-2-(4-methoxyphenyl)-4- phenyl-oxazolidine-5-carboxylic acid (IV). The present invention further provides the new intermediates isolated in the process for the preparation of docetaxel: - iV-Allyloxycarbonyl-(2J?,3S)-3-phenylisoserine methyl ester

(H),

(4S_?5JR)-iV-Allyloxycarbonyl-2-(4-methoxyphenyl)-4- phenyloxazolidine-5-carboxylic acid methyl ester (III),

- (4S,5i?)-iV-Allyloxycarbonyl-2-(4-methoxyphenyl)-4-phenyl- oxazolidine-5-carboxylic acid (IV),

- 7, 10-Diallyloxycarbonyl-10-deacetyϊbaccatin III (VI), - 13-[iV-Allyloxycarbonyl-2-methoxyphenyl-4-phenyl- 1,3- oxazolidine~5-carboxyl]-7, 10-diallyloxycarbonyl- 10- deacetylbaccatin III (VII),

13-[2-Methoxyphenyl-4-phenyl-l,3-oxazolidine-5- carboxyl]-10-deacetylbaccatin III (VIII).

In the preferred embodiment of the invention, the consecutive steps of the process for preparation of docetaxel are carried out in the following manner. Protecting of the amino group in (2i?,3S)-3-phenylisoserine methyl ester with allyloxycarbonyl is preferably performed by the reaction with allyl chloroformate in methylene chloride in the presence of sodium hydrogen carbonate.

(I) (H) Cyclization of JV^"-allyloxycarbonyl-(2i?,3S)-3~phenylisoserine methyl ester (II) to (4S,5i?)-i\T-allyloxycarbonyl-2-(4- methoxyphenyl)-4-phenyloxazolidine-5-carboxylic acid methyl ester (III) is performed by the reaction with 4-methoxybenzoate aldehyde or, more preferably, with its dimethyl acetal. The product may be purified by chromatography or crystallization, eg., from ethyl acetate.

Hydrolysis of (4S,5_JR)-i\T-allylox7caxbonyl-2-(4- methoxyphenyl)-4-phenyloxazolidine-5-carboxylic acid methyl ester (III) to (4S,5i?)-iV-allyloxycarbonyl-2-(4-methoxyphenyl)-4- phenyloxazolidine-5-carboxylic acid (IV) is carried out, for example, with the use of lithium hydroxide in methanol. The crude produ of synthesis.

(III) (^IV)

Protecting of C-7 and C-IO hydroxyl groups in 10- deacetylbaccatin III (V) with allyloxycarbonyl group is carried out in the reaction with allyl chloroformate (Aoc-Cl) in tetrahydrofuran in the presence of n-hexyllithium. The product

(VI) is crystallized, for example, from ethyl acetate.

Esterification of C- 13 hydroxyl group in 7,10- diallyloxycarbonyl-10-deacetylbaccatin III (VI) with (4-S,5R)-N- alylloxycarbonyl-2-(4-methoxyphenyl)-4-phenyloxazolidine-5- carboxylic acid (IV) is carried out by any method known in the art of taxane chemistry. Preferably, esterification is carried out by carbodiimide method, using dicyclohexylcarbodiimide (DCC) in the presence of 4- (iV,JV-dimethylamino) -pyridine (DMAP) in anhydrous toluene at the temperature of ca. 70⁰C. The product is purified by chromatography on silica gel or by crystallization, for example, from ethyl acetate.

Simultaneous removal of the protecting allyloxycarbonyl groups in the compound (VII) preferably occurs under the action of palladium(O) derivatives, preferably tetrakis(triphenylphosphine)palladium(0), in the presence of nucleophilic substance, such as diethylamine.

The compound (VIII) may be used in the next step of the synthesis without further purification.

Cleavage of oxazolidine ring in the compound (VIII) occurs, for example, in the reaction of pyridinium salt of p- toluenesulfonic acid (PPTS). The crude product - desBoc- docetaxel (IX) is purified by chromatography on silica gel.

Tlerύ-butyloxycarbonyl group is introduced to desBoc- docetaxel (IX) in the reaction with di-tert-butyl dicarbonate, carried out in methylene chloride in the presence of sodium hydrogen carbonate.

(IX) (X)

The obtained docetaxel (X) may be further purified, eg., by means of column chromatography.

The process of the invention provides an effective method for preparation of docetaxel, while eliminating inconveniences related to methods known in the art. The use of the same allyloxycarbonyl group for protecting both hydroxy! groups in

10-deacylbaccatin III and amino group in (4S,5R)-2- methoxyphenyl-4-phenyl- 1 ,3-oxazolidine-5-carboxylic acid allows easy removal of all protecting groups, JV- and O- allyloxycarbonyl, under mild reaction conditions, without causing loss of valuable compound and the need of its re- acetylation.

The invention is further illustrated by the following, non- limiting, examples.

Example 1 iV-Allyloxycarbonyl-(2i?,3(S5-3-phenylisoserine methyl ester (II)

A_{ocC|i NaHC}o₃ AocNH

(I) (H) (2i?,3SJ-3-Phenyl-isoserine methyl ester (I) hydrochloride (50 g, 0.22 M) is dissolved in 1.55 L of methylene chloride, then sodium hydrogen carbonate NaHCO3 (400 g) and, finally, allyl chloroformate (25.5 mL, 0.24 M) are added. The reaction mixture is stirred mechanically at room temperature overnight until the substrate (I) disappeared (TLC control). The mixture is filtered, the precipitate of NaHCO₃ is washed with methylene chloride (150 mL and 100 mL), the filtrate and washings are combined and evaporated under reduced pressure to the volume of approx. 100 mL. As a result of gradual addition of 600 mL of hexane and keeping the reaction mixture at the temperature of 5-10°C, the product in the form of white precipitate is crystallized, filtered and dried in the air. Yield: 54.0 g (89.5%) HPLC 94,4 %; TLC: Rf = 0,22 (I), 0,80 (II), (10: 1 = CHCl₃/MeOH); [α]_D ²⁰ = + 6,4° (c=0,44 CHCl₃);

IR (KBr) cm -¹: 3489, 3355, 3034, 2962, 1740, 1698, 1528, 1496, 1444, 1370, 1256, 1142, 1103, 1053, 704;

¹H-NMR (200 MHz, CDCl₃), δ: 7,25-7,39 (m,5H,Ph); 5,75- 5,98 (m,lH, =CH-), 5,72 (d,lH,J=9,7Hz,NH); 5,17-5,31 (m,3H; C- 3H i CH₂=); 4,48-4,55 (m,3H; C-2H i -CH₂O); 3,84 (s,3H, COOCH₃), 3,24 (d,lH, J=4,4)

¹³C-NMR (CDCl₃) δ: 53, 16 (COOCH₃); 56,01 (C3); 73,3 (C2); Aoc: 65,82 (-CH₂-O-), 117,80 (CH₂=), 132,53 (=CH-); 126,70, 127,85, 128,62 i 138,82 (Ph); 155,48 (CO-Aoc) i 173,21 (CO- ester)

Example 2 (4 S, 5R) -iV-Allyloxycarbonyl-2-(4-methoxyphenyl) -4-phenyloxazo- lidine-5-carboxylic acid methyl ester (III)

To the mixture of iV-allyloxycarbonyl-(2i?,3S)-3-phenylisoserine methyl ester (II) (20.66 g, 0.074 M) and dimethylacetal of p- anisal aldehyde (13.5 mL, 0.08 M) in toluene (560 mL), pyridinium salt of p-toluenesulfonic acid is added (1.86 g, 0.074 M) and the solution is heated until boiling; the reaction is controlled by TLC chromatography [hexane-ethyl acetate 5:2; Rf (II) = 0.21, Rf (III) = 0.41]. After 11 -hour heating under reflux, most of the solvent is evaporated under the reduced pressure (to the volume of approx. 60 mL) and 150 mL of cyclohexane is added dropwise to the cooled solution of the product. The resulting yellowish oil is recrystallized from ethyl acetate. After two recrystallizations, pure product (III) is obtained (96.8%, ace. to HPLC); yield 19.3 g (65.7%) [α]D²⁰ = - 38,9° (c= 12,9 MeOH); IR (KBr) cm -¹: 3462, 3054, 2952, 2842, 1739, 1703,

1613, 1513, 1394, 1244, 1066, 969, 779, 730, 588; ¹H-NMR (200 MHz, CDCl₃), δ: 7,25-6,85 (m,9H); 6,50-6,42 (m, lH); 5,88-5,68 (m, lH), 5,35 (d,lH,J=3,4Hz); 5,13-5,0 (m,2H); 4,87 (d,lH,J=3,4Hz); 4,62-4,52 (m,2H), 3,85(s,3H); 3,81 (s,3H)

¹³C-NMR (CDCl₃) 6: 160,5; 154,3; 139,2; 132,1; 130,0; 128,8; 128,6; 128,4; 128,0; 126,9; 117,6; 113,6; 91,4; 81,8; 66,3; 63,6; 55,3; 52,7

Example 3

(4S,5i?)-iV-allyloxycarbonylo-2-(4-methoxyphenyl)-4-pheny- loxazolidine-5-carboxylic acid (IV)

(III) (IV)

Ester (III) (3.0 g, 7.55.mM) is dissolved in 100 mL of methanol and 34 mL 0.5 M aqueous solution of lithium hydroxide is added while stirring. The course of the reaction is controlled by TLC chromatography [hexane-ethyl acetate 5:2; Rf (III) = 0.41, Rf (lithium salt of acid (IV) 0.01]. After the end of the reaction (2 hours), the reaction mixture is concentrated to dryness under reduced pressure, 140 mL of water and 20 mL of methylene chloride are added. The mixture is acidified while stirring to pH « 3, adding 0.5 M solution of HCl. After separation of the layers, aqueous phase is extracted with three portions of methylene chloride (3 x 50 mL) and the combined extracts are washed with brine solution (50 mL). Drying of the extract over MgSO₄ and evaporation of the solvent gave the compound (IV); yield 2.84 g (98%), purity appropriate for further synthesis (> 90% ace. to HPLC). [Q]D²⁰ = - 23,7° (c= 12,2 MeOH);

IR (KBr) cm -¹: 3416, 2935, 2837, 1705, 1622, 1513, 1400, 1251, 1172, 1031, 765, 699, 588;

¹H-NMR (200 MHz, CDCl₃), δ: 7,42-6,85 (m,9H); 6,53 (s,lH); 5,88-5,69 (m,lH), 5,35(d,lH, J=3,3 Hz); 5,13-5,02 (m,2H); 4,93 (d, lH;J=3,3 Hz); 4,58-4,55 (m,2H), 3,81 (s,3H)

^1SC-NMR (CDCl₃) δ: 174,3; 154,5; 138,9; 131,9; 129,7; 128,7; 128,6; 128,1; 126,9; 117,7; 113,6; 91,4; 81,4; 66,5; 63,5; 55,3; 50,7 MS m/z: 384,1(M+H) \ 406,1 (M+Na)⁺, 789,2 (2M+Na)⁺

Example 4 7,10-Diallyloxycarbony.l-lO-deacetylbaccatin III (VI)

hexLi, THF AocCI

In a dried flask, 10-deacetylbaccatin III (DAB 27.2.g, 50 mM) is suspended under nitrogen in anhydrous tetrahydrofuran (THF) (1.5 L) and the suspension is stirred until dissolution (temperature < 30° C). Then the solution is cooled to the temperature of -78° C and the n-hexyl lithium solution (52 mL, 2.5 M solution in hexane) is added dropwise; while observing precipitation of lithium salt. After 10 minutes, the solution of allyl chloroformate (13.5 mL, 127.2 mM) in anhydrous THF (30 mL) is added dropwise to the stirred suspension. The clear solution was warmed to 0°C within 2 hours. The course of the reaction is controlled by TLC [ethyl acetate - toluene 1:1; Rf (V) = 0.15, Rf (VI) = 0.54]. After the completion of the reaction (2.5 hours), the reaction mixture is poured into aqueous saturated solution of NH4CI (1.5 L). THF is removed by concentration under reduced pressure. The product is extracted with ethyl acetate (300, 150 and 100 mL L). The combined extracts are washed with saturated brine, dried over MgSO4 and evaporated under reduced pressure to obtain 44.2 g of crude product. The product is crystallized from ethyl acetate to obtain 26.55 g (yield 74.5%) of the pure compound (V) (97.7% according to HPLC);

[α]D²⁰= -72,7 ° (c 1,0, MeOH);

IR (KBr) cm -¹: 3543, 3461, 2947, 2894, 1754, 1724, 1702, 1452, 1381, 1262, 1109, 1057, 992, 938, 782, 718, 640, 611, 468 iH-NMR (200 MHz, CDCl₃), δ: 8,19-7,41 (m,5H); 6,25 (s,lH); 6,18-5,86 (m,2H); 5,64 (d,lH,J=7 Hz); 5,52 (dd, lH,J=7Hz); 5,42-5,24 (m,8H); 4,99(d,J=9Hz,lH); 4,32(d,lH); 4,86 (br t,lH); 4,08 (d,lH); 3,88 (d,J=7Hz,lH); 2,62(m,lH); 2,30(s,3H); 2,29(m,2H); 2,04 (s,3H); 1,96 (m,lH); 1,81 (s,3H); l,13(s,3H); 1,08 (s,3H) 1³C-NMR (CDCl₃) δ: 202, 1; 170,7; 166,9; 154,0; 153,9;

145,8; 133,7; 131,9; 131,3; 131,5; 129,2; 128,7; 119,2; 118,7; 83,8; 80,5; 78,7; 75,5; 69,0; 68,8; 67,9; 56,2; 47,3; 42,6; 38,3; 33,4; 26,5; 22,6; 21,0; 20,1; 15,4; 14,2; 10,5; MS m/z: 735,6 (M+Na)⁺, 1448,0 (2M+Na)⁺

Example 5

13-[iV-Allyloxycarbonyl-2-methoxyphenyl-4-phenyl-l,3-oxazoli- dine-5-carboxyl]-7, 10-diallyloxycarbonyl-lO-deacetylbaccatin HI (VII)

(4 S, 5R) -iV-allyloxycarbonylo-2- (4-methoxyphenyl) -4- phenyloxazolidine-5-carboxylic acid (IV, 0,437 g, 1,14 mM) is dissolved in 10 mL of distilled toluene and 7,10- diallyloxycarbonyl-10-deacetylbaccatin (VI, 0.542 g, 0.76 mM); 4-(iV,JV~dimethylamino)-pyridine (DMAP) 0.014 g (0.11 mM) and dicyclohexylcarbodiimide (DCC) 0.235 g (1.14 mM) are added while stirring. Then the flask is placed in an oil bath at the temperature of 70-75⁰C. The course of the reaction is controlled with the use of TLC in toluene : ethyl acetate system (6:4) [Rf (VI) = 0.19, Rf (VII) = 0.56]. After 1 hour, the substrate (VI) is no longer detected. After cooling the reaction mixture, dicyclohexylurea is filtered off, and the filtrate is concentrated under the reduced pressure. The obtained precipitate is dissolved in 30 mL of ethyl acetate and washed subsequently with saturated solution of NaHCOe (15 mL), 0.1 M solution of HCl (15 mL) and 15 mL of saturated aqueous NaCl solution. The organic layer is dried over MgSθ4, the solvent is evaporated under the reduced pressure. 0.88 g of compound (VII) is obtained in the form of a foam of 78.9% HPLC purity (yield 82%). The product is purified chromatographically on silica gel (approx. 180 g), while eluting with the following solvent system toluene : ethyl acetate (8:2). After evaporation of suitable fractions, 1.86 g of the product was obtained in the form of white foam (HPLC purity 86.9%). The sample of crude product was also purified by recrystallization from ethyl acetate / hexane to obtain white precipitate (purity 83.0% according to HPLC). The product was used for further synthesis. iH-NMR (200 MHz, CDCl₃), δ: 8,06- 6,90(m,9H); 6,58(s, lH); 6,22 (t,lH); 6,07-5,88 (m,3H); 5,66 (d,lH,J=7,4Hz); 5,52 (dd, lH,J=7Hz); 5,46-4,52 (m,13H); 4,92 (m.lH); 4,29(d,lH); 4,12(d, lH); 3,94(d,J=7Hz,lH); 2,62(m,2H); 2,36(s,3H); 2,26(m,2H); 1,94 (s,3H); 1,82 (s,3H); l,26(s,3H); 1,18 (s,3H) (MS) m/z: 1100,4 (M+Na)⁺

Example 6

13~[2-Methoxyphenyl-4-phenyl- 1 ,3-oxazolidine-5-carboxyl]- 10- deacetylobaccatin III (VIII)

13- [iV-Allylocarboxycarbonyl-2-methoxyphenyl-4-phenyl-

1 ,3-oxazolidine-5-carboxy]-7, 10-diallyloxycarbonyl- 10- deacetylbaccatin III (VII, 2.86 g, 2.65 mM) is dissolved in 50 mL of dry THF; then 0.335 g of tetrakis(triphenylphosphine)palladium and 0.83 mL of diethylamine are added under nitrogen. The reaction mixture is stirred at room temperature, while controlling the course of the reaction by TLC chromatography [CHCl₃ : MeOH (95:5), Rf (VII) = 0.83, Rf (VIII) = 0.32 and ethyl acetate : toluene (2:8) R_f (VII) 0.51, Rf (VIII) = start ]. After 2 hours, the substrate is no longer detected; after evaporation of the solvent, the crude product (VIII) in the form of a foam is used for the next step of the process. Example 7

13-[(2i?,3S)-3-Phenyl-isoserine]-10-deacetylbaccatin III (desBoc- docetaxel)

To the solution of crude 13~[2-methoxyphenyl~4-phenyl- l,3-oxazolidine-5-carboxyl]-10-deactylbaccatin III (VIII) from the former step (2.19 g, approx. 2.6 mM) in 80 mL of methanol, PPTS is added (1.66 g). The reaction is carried out at room temperature, while controlling its course by TLC chromatography [CHCl₃ : MeOH (9:1); Rf (VIII) = 0.75, Rf (IX) = 0.14]. After 24 hours, the solvent is evaporated. The crude product in the form of a foam is dissolved in 130 mL of ethyl acetate and washed three times with saturated aqueous NaHCO3 solution (3 x 50 mL), and then with saturated NaCl solution (50 mL). The organic layer is dried over MgSθ4. The filtrate is evaporated to obtain orange foam. The product is purified chromatographically on silica gel, while eluting the product with methylene chloride - methanol (98:2, then 95:5 and finally 90: 10). After evaporation of suitable fractions 1.06 g of product (IX) is obtained of 97.0% purity (HPLC).

¹H NMR: δ (ppm): 8,08-7,36(m,10H.); 6, 12 (t,J=9,0,lH); 5,64 (d,J=7,l, IH); 5,20 (s, IH); 4,93 (d, J=7,7,1H); 4,35- 4, 13(m,5H); 3,86(d,J=7,lH); 2,65-2,50 (m, 1/2C6-H); 2,25 (s, 3H); 2,02(m,2H); l,90(s,3H); l,83(m,lH); 1,74 (s,3H): 1,22 (s,3H); l,ll(s,3H) MS(ESI)

708,3 (M+H) ⁺, 730,3(M+Na)⁺

Example 8 Docetaxel

(IX) (X)

13-[(2i?,3S)-3-Phenyl-isoserine]-10-deacetylbaccatin III (desBoc- docetaxel, IX), (1,0 g, 1,41 mM) is dissolved in 50 mL of methylene chloride, then sodium hydrogen carbonate (3.29 g, 35 mM) and, in the end, di-tert-butyl di-carbonate (0.69 mL, 2.99 mM) are added. The reaction mixture is stirred at room temperature until the substrate (IX) disappears (approx. 20 hours), while controlling the reaction progress by TLC chromatography (CHCI3: MeOH 9: 1). The mixture is filtered, NaHCθ3 precipitate is washed with methylene chloride (2 x 10 mL), the filtrate and washings are combined and evaporated. The crude product (1.69 g) is purified by column chromatography on silica gel in the system of chloroform : methanol 98:2, and then 97:3 and 96:4; appropriate fractions are combined and evaporated under the reduced pressure; 787 mg of docetaxel of 99.03 % purity (according to HPLC) is obtained. Physicochemical data of the product are in compliance with the literature data (US 4,814,470). [α] 2³ _D= - 42,2 ° (c = 0,74, ethanol)

¹H NMR: δ (ppm): 8,12-7,65(m,10H,CH aromt); 6,21 (t,J=8,7,C~ 13H); 5,67 (d,J=7,C2-H); 5,47(d,J=9,2,C-3'-H); 5,27 (br,NH); 5,20 (s,C-10H); 4,94 (dd, J=7,7 i 2, 1C-5H); 4,61(m,C-2'-H); 4,07- 4,34 (m, C-20-H i C-7); 3,91(d,J=7,2,C-3H); 2,54-2,66 (m, 1/2C6-H); 2,37(s,CH₃ acetyl); 2,26(d,J=8,7,C14-H); 1,85 (1/2C6- H i s,C18-H); 1,76 (s,C-19-H): l,35(s,9H, Boc)l,24 (s,C-17H); l,13(s,C-16-H)

¹³C NMR: C-9(C=O) 211,3; C- 1'(C=O) 172,7; C4(C=Oacetyi) 170,3; C2(C=O)benzoyil67,0; C=O(BOc) 155,4; C-12 138,5; C-l(phenyl at C-30 136,0; C-I (benzoyl) 129,2; C (aromatic + C-I l) 133,7, 130,2; 129,2, 128,7; 128,7, 128,1, 126,8; C-5 84,2; C-4 81,1; C-I 80,3; C(CHs)₃ 78,8; C-20 76,6; C-10 74,8; C-2 73,7; C-2' 72,4'; c-13 72,0; C-8 57,7; C-3' 56,2; C-3 46,5; C-15 43,1; C-14 37,0; C-6 35,7; C(CHs)₃ 28,2; C- 16 26,5; CH₃ (acetyl at C-4) 22,6; C-18 14,3; C-19 9,9.

UV (methanol): λ_max = 230 nm (16150); 275 nm (1075); 285 nm (1670) IR (KBr): 3459, 3061, 2981, 1720, 1702, 1602, 1585, 1491, 1452, 1370, 1248, 1164, 1096, 1071, 1024, 981, 877, 848, 780, 709, 572, 522 cm -ⁱ

(MS(Turbo Spray) m/z: 809 (M+H)⁺, 831(M+Na)⁺, 1639(2M+Na)⁺

Claims

1. A process for the preparation of docetaxel characterized in that it comprises

(i) Simultaneous protection of the hydroxyl groups at C-7 and C-IO position of lO-deacetolobaccatin III and amino group of (4S,5R)-2-methoxephenyl-4- phenyl- 1 ,3-oxazolidine-5-carboxylic acid with allyloxycarbonyl to give 7, 10-diallyloxycarbonyl-10- deacetylbaccatin III (VI) and {4S,5R)-N- allyloxycarbonyl-2-(4-metoxyρhenyl)-4- phenyloxazolidine-5-carboxylic acid (IV), respectively,

(ii) Esterification of the hydroxyl group at C- 13 position in 7, 10-diallyloxycarbonyl-lO-deacetylbaccatin III (VI) with (4S,5i?)-JV-allyloxycarbonyl-2-(4- metoxyphenyl)-4-phenyloxazolidine-5-carboxylic acid (IV) in the presence of condensing agent and a base, to give 13-[N-allyloxycarbonyl-2- methoxyphenyl-4-phenyl- 1 ,3-oxazolidine-5- carboxyl]-7, 10-diallyloxycarbonyl- 10- deacetylbaccatin (VII),

(iii) Simultaneous removal of allyloxycarbonyl protective groups in 13-N-allyloxycarbonyl-2-methoxypenyl-4- phenyl- 1 ,3-oxazolidine-5-carboxyl]-7, 10- diallyloxycarbonyl-10-deacetylbaccatin III (VII) to give 13-[2-methoxyphenyl-4-phenyl- 1 ,3-oxazolidine- 5-carboxyl]-10-deacetylbaccatin III (VIII), (iv) Cleavage of the oxazolidine ring in 13-[2- methoxyphenyl-4-phenyl- 1 ,3-oxazolidine-5- carboxyl]-10-deactylbaccatin (III) to obtain desBoc- docetaxel (IX), (v) Acylation of the amino group of desBoc-docetaxel

(IX) to give docetaxel (X), and

(vi) Optionally, purification of docetaxel (X).

2. The process according to claim 1 characterized in that compound (VI) is obtained in the reaction of 10-deacetylbaccatin III with allyl chloroformate.

3. The process according to claim 1 characterized in that the condensing agent is dicyclohexyldiimide.

4. The process according to claim 1 characterized in that a base is 4-diethylaminopyridine.

5. The process according to claim 1 characterized in that allyloxycarbonyl groups in compounds (VII) are removed with the use of palladium(O) derivative in the presence of nucleophillic substance.

6. The process according to claim 5 characterized in that Palladium(O) is tetrakis(triphenylphosphine)palladium(0).

7. The process according to claim 5 characterized in that the nucleophillic substance is diethylamine.

8. The process according to claim 1 characterized in that cleavage of oxazolidine ring in compound (VIII) is carried out in acidic conditions.

9. The process according to claim 8 characterized in that cleavage of oxazolidine ring in compound (VIII) is carried out with the use of pyridinium salt of p- toluenesulfonic acid.

10. The process according to claim 1 characterized in that amino group in compound (IX) is acylated with di- teri-butyl dicarbonate.

11. iV-Allyloxycarbonyl- (2R, 3 S) -phenylisoserine methyl ester.

12. (4,S,5i?)-iV-Allyloxycarbonyl-2-(4-metoxyρhenyl)-4- phenyloxazolidine-5-carboxylic acid methyl ester.

13. (4S,5J?)-JV-allyloxycarbonyl-2-(4-metoxyphenyl)-4- phenyloxazolidine-5-carboxylic acid.

14. 7,10-Diallyloxycarbonyl-lO-deactylbaccatin III.

15. 13-[iV-Allyloxycabonyl-2-methoxyphenyl-4-phenyl-

1 ,3-oxazolidine-5-carboxyl]~7, 10-diallyloxycarbonyl- 10- deacetylbaccatin III (VII) .

16. 13-[2-Methoxyphenyl-4-phenyl- l,3-oxazolidine-5- carboxyl]-10-deacetylbaccatin III (VIII).

17. A process for the preparation of (4S,5R)-N- allyloxycarbonyl-2-(4-metoxyphenyl)-4- phenyloxazolidine-5-carboxylic acid (IV) characterized in that in comprises:

(i) protection of the amino group (2R,3S}-3- phenylisoserine methyl ester (I) with allyloxycarbonyl, to obtain iV-allyloxycarbonyl-(2i?, 3 S) -3 -phenylisoserine methyl ester (II), (ii) cyclization of iV-allyloxycarbonyl-(2i?,3S)-3- phenylisoserine methyl ester (II) to (4S,5i?)-iV-aHyloxycarbonyl-2- (4-methoxyphenyl)-4-phenyloxazolidine-5-carboxylic acid methyl ester (III),

(iii) hydrolysis of compound (III) to (4S,5R)-N- allyloxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-oxazolidine~5- carboxylic acid (IV).

18. The process according to claim 17 characterized in that iV-allyloxycarbonyl-(2i?,3S)-3-phenylisoserine methyl ester (II) is cyclized in the reaction with 4-methoxybenzaldehyde or its dimethyl acetal.

19. The process according to claim 18 characterized in that i\T-allyloxycarbonyl-(2i?,3S)-3-phenylisoserine methyl ester (II) is cyclized in the reaction of dimethyl acetal of 4- methoxybenzaldehyde .

20. The process according to claim 17 characterized in that (4S,5i?)-i\T-allyloxycarbonyl-2-(4-metoxyρhenyl)-4- phenyloxazolidine-5-carboxylic acid methyl ester (III) is hydrolized with the use of lithium hydroxide in methanol.