BRIEF DESCRIPTION OF THE DRAWING
FIGURE 1 is the representative reaction scheme of the process of the invention.
FIGURE 2 is the structural representation of N-debocdocetaxel or 10-deacetyl-N-
debenzoyl paclitaxel (I).
FIGURE 3 is the structural representation of 7,10-di-O-[2-(chloroacetyl)]-13- .
[(4S,5R)-2-(p-methoxyphenyl)-3-benzyloxy-carbonyl-4-phenyl-l,3-oxazolidinyl]-
10-deacetylbaccatin III (V). ' •
FIGURE 4 is the structural representation of 7,10-di-O-chloroacetyl-10-
deacetylbaccatin III(III).
FIGURE 5 is the structural representation of (4R,5S)-5-ethoxyoxycarbonyl-2-(4-
methoxyphenyl)-4-phenyl-3-benzyloxy-carbonyl-l,3-oxazolidine (IV).
FIGURE 6 is the structural representation of 13-(3'-N-Benzyloxycarbonyl-
phenyl-isoserine)-7,10-di-O-chloroacetyl-10-deactylbaccatin III (VI).
FIGURE 7 is the . structural representation of 13-(3'-N-Benzy
loxycarbonylphenylisoserine)-10-deactylbaccatin III (VII).
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an improved process for the preparation of N-debocdocetaxel or 10-deacetyl-N-debenzoyl paclitaxel (I), an intermediate for the preparation of paclitaxel and docetaxel, in high yield and purity.
The process comprises the coupling of 7,10-di-O-chloroacetyl-10-deacetylbaccatin III, (III) with • (4R,5S)-5-ethoxyqxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-3-benzyloxycarbonyl-l,3-oxazolidine (IV) to give 7,10-di-O-[2-(chloroacetyl)]-I3-[(4S,5R)-2-(p-methoxyphenyl)-3-benzyloxy-carbonyl-4-phenyl-l,3-oxazolidinyl]-10-deacetylbaccatin III (V)in the presence of DCC (dicyclohexylcarbodiimide)and DMAP (4-dimethylamino-pyridine)at 50°G. The product was purified by slurry wash with methanol (99.89% purity by High-performance liquid chromatography (HPLC)).

7,10-di-O-chloroacetyl-10-deacetylbaccatin HI, (III) was prepared according to the procedure US2004/0073 044.
(4R,5S)-5-ethoxyoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-3-benzyloxy-carbonyl-l,3-oxazolidine (IV) was prepared according to Journal of Medicinal Chemistry; vol. 48, nb. 7; (2005); p. 2655-2666.
Opening of the oxazolidine ring was performed under mild conditions using formic acid in acetonitrile to give 13-(3'-N-Benzyloxycarbonylphenylisoseiine)-7,10-di-O-chloroacetyl-10-deactylbaccatin III (VI).
The protected chloroacetyl groups at 7- and 10- position of the baccatin III were deprotected under mild conditions using 25% ammonia in tetrahydrofuran to achieve 13-(3'-N-Benzy loxycarbonylphenylisoserine)-10-deactylbaccatin III (VII). .
The amine protected benzyloxy carbonyl group was deprotected by the usual procedure using 5% Pd/C under hydrogen atmosphere of 50 psi, which leads to the formation of crude N-debocdocetaxel. The crude was given acid base treatment, passed through short pad silica (200 - 400 mesh) bed and eluted with acetone/hexane. The resulting material was further recrystallized from 50% tetrahydrofuran and diisopropyl ether to give N-debocdocetaxel (I) (HPLC: 99.61% epiisomer 0.2%).
The invention can be explained in greater detail with the help of the accompanying examples/ experiments.

EXPERIMENTAL DETAILS
Example-1
A solution of 7, 10-di-O-chloroacetyl-lO-deacetylbaccatin III, (30 gm) in toluerie (450 ml) was treated with 26.1 gm of (IV), 17.2 gm of dicyclohexylcarbodiimide (DCC), 0.262 gm of dimethylamino pyridine (DMAP) at 50°C for 3hr. After completion of the reaction, cooled the reaction mixture to 0-5°C and filtered, washed the solid with 60 ml of toluene. The combined toluene layer washed with brine and water. The toluene layer was evaporated to dryness and then recrystallized from methanol to yielding 93% with 99.89% HPLC purity.
Example-2 ■ A solution of example 1 (30 gm) in acetonitrile (300 ml) was treated with formic acid (300ml) at 20°C for 18hr. After completion of the reaction, quenched the reaction mixture with sodium bicarbonate and then extracted with ethylacetate (3x 30ml). The combined ethyl acetate layer was dried over sodium sulphate and distilled out in Rota vapor to dry ness to get the crude (VI), which was recrystallized from tert-butyl methyl ether and heptane (3:4). Yield 87% with 95% to 98% HPLC purity.
Example-3
A solution of example 2 (25 gm) in THF (125 ml) was treated with concentrated ammonia and stirred the reaction mixture at room temperature for 5 to 6 hr. After completion of the reaction, neutralized the reaction mixture with IN HC1 and extracted with ethyl acetate (3x50ml). Combined ethyl acetate layer was dried over sodium sulphate and then distilled out in Rota vapor to dryness. This crude was dissolved in MDC and passed through short pad silica gel (200-400 mesh) and then recrystallized from tert-buty\ methyl ether and heptane (3:4). Yield 90% with 95% to 98% HPLC purity.

Example-4
1.5 gm of example 3 was dissolved in 225 ml of tetrahydrofuran and treated with 5% Pd/C (3 gm). The reaction was stirred vigorously overnight under an atmosphere of hydrogen. The reaction mixture was filtered through a bed of celite (15gm). It was washed with tetrahydrofuran (45ml) and then distilled out in the Rota vapor, under vacuum to get the crude. The crude was dissolved in ethyl acetate (30 ml) and added 1NHC1 (60ml) stirred the biphasic mixture for 30 min at room temperature. Separated the ethyl acetate layer and repeated the same for another three times. The aqueous layer was basified with 25% ammonia solution and then extracted with ethyl acetate 93x50ml). The resulting solid was dissolved in acetone and passed through a short pad silica gel (200-400 mesh) and eluted with 15% acetone in hexane. The eluted acetone/hexane mixture was distilled out in Rota vapor to dryness. The resulting solid was recrystallized from tetrahydrofurn/diisopropyl ether yielding 90% of N-debocdocetaxel, with HPLC purity 99.68%, 7-epi analogue less than 0.2 and chemical assay: 90 - 92%:

We claim:
1. A process for the synthesis of N-debocdocetaxel or 10-deacetyl-N-debenzoyl paclitaxel (I) comprising the following steps:
a) coupling of 7,10-di-O-chloroacetyl-10-deacetylbaccatin III (III) with (4R,5S)-5-thoxyoxycarbonyl-2-(4-methoxyphenyl)-4-phenyl-3-benzyloxycarbonyl-l,3-oxazolidine (IV) to give 7,10-di-O-[2-(chloroacetyl)]-13-[(4S,5R)-2-(p-methoxyphenyl)-3-benzyloxycarbonyl-4-phenyl-l,3-oxazolidinyl]-10-deacetylbaccatin III (V) in the presence of a condensing agent,
b) cleaving the oxazdlidine ring to give 13-(3'-"N-Benzyloxycarbonylphenylisoserine)-7,10-di-O-chloroacetyl-10-deactylbaccatin III, (VI),
c) deprotection of chloroacetyl groups of compound (VI) to achieve 13-(3'-N-Benzyloxycarbonylphenylisoserine)-10-deactylbaecatin III, (VII),
d) deprotection of benzoyloxy group from 13-(3'-N-Benzyloxycarbonylphenylisoserine)-10-deactylbaccatin III giving the crude debocdocetaxel,
e) purification and recrystallization of the crude debocdocetaxel to obtain N-debocdocetaxel of purity95% to 98%.
•2. A process according to claim 1 wherein step (a) is carried out in the presence of the condensing agent is dicyclohexylcarbodiimide and the activating agent is 4-dimethylamino-pyridirie at 50°C.
3. A process according to claim 2 wherein the obtained product is purified by slurry wash with methanol to obtain 99.89% purity by High-performance liquid chromatography (HPLC).
4. A process according to claim 1 wherein step (b) is performed using formic acid in acetonitrile.

5. A process according to claim 1 wherein step (c) comprises deprotection of the protected chloroacetyl groups at 7- and 10- position of the baccatin III using 25% ammonia in tetrahydrofuran to achieve 13-(3'-N-Benzyloxycarbonyl-phenylisoserine)-10-deactylbaccatin III, (VII).
6. A process according to claim 1 wherein step (d) is performed in the presence of 5% Pd/C under hydrogen atmosphere of 50 psi.
7. A process according to claim 1 wherein the crude debocdocetaxel obtained in step (d) is subjected to an acid base treatment, passed through short pad silica (200 - 400 mesh) bed and eluted with acetone/hexane.
8. A process according claim 7 comprising recrystallization from 50%
tetrahydrofuran and diisopropyl ether to give of high purity
9. A process according to claim 8 wherein the N-debocdocetaxel (I) has a HPLC
purity of 99.68% and with a content of corresponding epi isomer of 0.2%.