FORM 2 THE PATENTS ACT, 1970 (39 of 1970) & The Patents Rules, 2003 COMPLETE SPECIFICATION (See section 10; rule 13) 1. Title of the invention. - "Novel process for the preparation of Telithromycin" 2. Applicant(s) (a) NAME : ALEMBIC LIMITED (b) NATIONALITY : An Indian Company. (c) ADDRESS : Alembic Campus, Alembic Road, Vadodara-390 003, Gujarat, India. 3. PREAMBLE TO THE DESCRIPTION The following specification particularly describes the invention and the manner in which it is to be performed: Field of the invention The present invention relates to the process for the preparation of Telithromycin of formula (I) or pharmaceutical^ acceptable salts thereof. It also provides novel intermediates and process for the preparation of the same. Telithromycin of formula (I) is know to have antibiotic activity. Background of the invention Macrolide compounds are known for anti bacterial activity. The rapid development of antibiotic resistance among the major respiratory pathogens has created a serious problem for the effective management of respiratory tract infections. There is a great medical need for new antibiotics to address the problem of antibiotic resistance. Under these circumstances, several novel series of macrolides with a common C-3 ketone group were recently introduced, which are collectively known as ketolides. Ketolides represent a novel class of macrolide antibiotics that have received much attention recently on account of their excellent activity against resistant organisms. Most ketolides are derivatives of erythromycin, a potent and safe antibiotic widely prescribed for the treatment of respiratory tract infections for more than four decades. Ketolides are 14-membered ring macrolide derivatives characterized by a keto group at the C-3 position [Curr. Med. Chem. - Anti-Infective Agents, 2002, 1, 15-34]. Several Ketolide compounds are under clinical 2 investigation. However, Telithromycin of Formula (I) is the first agent to receive approvable status in this class of drugs. US5635485 discloses several ketolide compounds, which are prepared by condensing compounds of formula (II) with amine of formula (III) in a solvent for prolonged hours to yield compound of formula (IV), followed by removal of protecting group Z' at 2' position by hydrolysis as shown in SCHEME -1. Furthermore, formula (II) is prepared by following the process disclosed in US5527780. wherein, definition of R and Z' is as described in above referred patent. Accordingly, Telithromycin is prepared by condensing compound of formula (II) with amine of formula (III), wherein followed by removal of the protecting group to yield Telithromycin of formula (I). 3 The process described in US5635485 suffers several drawbacks like: (i) Condensation of compound of formula (II) with formula compound of (III) is cumbersome. Moreover it is very difficult to remove unreacted reagents and impurities formed during the reaction, (ii) The isolation and purification of the desired compound of formula (I) cannot be done without laborious column chromatography, which is operationally difficult at commercial production level. Current Medicinal Chemistry, 2001, Vol. 8, 1727-1758 also describes the process for the preparation of various ketolides, including Telithromycin in which Clarithromycin (formula V) is reacted with hydrochloric acid to remove cladinose ring at C-3 position (formula VI) followed by selective acetylation of the 2'-hydroxy group in formula VI and selective oxidation of the 3-hydroxy group generated ketolide of formula VII. Further, 11-hydorxy group of compound of formula (VII) is selectively mesylated followed by base induced P- elimination to furnish a,(3-unsaturated ketone (formula VIII). The compound of formula (VIII) is further treated with sodium hydride and carbonyldiimidazole to form 12-O-acyl imidazole of formula (II), which upon stereoselective cyclization with (4-(3-pyridinyl)-imidazol-l-yl)-butylamine and subsequent deprotection of the 2'-hydroxy group gives Telithromycin of Formula (I). This process is outlined in following SCHEME-2 4 However, this process also suffers from similar drawbacks as listed above. Moreover the use of NaH is hazardous and extremely difficult to handle at the plant scale due to its pyrophoric nature. In light of the above difficulties for the preparation of Telithromycin, there exists a need to develop a process which is suitable for large scale production. Objects of the invention It is therefore an object of present invention to provide a process for the preparation of Telithromycin of formula (I) or pharmaceutically acceptable salts thereof. Another object of the present invention is to provide a process for the preparation of Telithromycin, which would be high yielding, cost 5 effective, easy to operate at industrial scale and would not involve the use of moisture sensitive, pyrophoric compounds like sodium hydride. A further objective of the invention is to provide a process of manufacture of Telithromycin that would involve selective mild reaction conditions. A further object of the invention is to provide a process of manufacture of Telithromycin that would be industrially feasible. Yet, another object of the present invention is to provide a novel compound of formula (XI), (XII) and (XIII), which are useful intermediates for the preparation of Telithromycin of formula (I) or pharmaceutically acceptable salts thereof. Summary of the invention In accordance with the object of the present invention, one aspect provides the process for the preparation of Telithromycin of formula (I) or its pharmaceutically acceptable salts wherein R is comprises steps of, (a) reacting compound of formula (IX) 6 with carbonyldiimidazole in the presence of polar solvent and a base to obtain the compound of formula (X) o C N II \\ HjC-^lL .,>>CH:> ' If I H3C-^ ^CH3 H=C>1> l H3C,, j..'0"3 ,0"'l^CH3 1 J, ^N^VH, o ^r ''o„ CH3 | [^ (X) ^*^ 0R2 * ' H3>' I O H3C, I 'CH3 ' ''"'f^l CH -X J ° CH3 O^^^T^ ''OH CH3 (XII) (f) treating compound of formula (XII) with an alcohol to obtain compound of formula (XIV) (g) selectively oxidizing compound of formula (XIV) in the presence of an oxidizing agent. 3. A process as claimed in claim 1 and 2, wherein said polar solvent in step (a) is selected from dimethylformamide, tetrahydrofuran, acetonitrile and the like or mixtures thereof. 30 4. A process as claimed in claim 1 and 2, wherein said base in step (a) is selected from DBU, triethylamine and diisopropylethylamine. 5. A process as claimed in claim 1 and 2, wherein said protecting group is selected from group comprising of trimethylsilyl group, a triethylsilyl group, an isopropyldimethylsilyl group, a tert-butyldimethylsilyl group, a (triphenylmethyl)dimethylsilyl group, a tert-butyldiphenylsilyl group, a diphenylmethylsilyl group, diphenylvinylsilyl group, a methyldiisopropylsilyl group, a tribenzylsilyl group, a tri(p-xylyl)silyl group, a triphenylsilyl group, a diphenylsilyl group and a dimethyloctadecylsilyl group. 6. A process as claimed in claim 1 and 2, wherein said polar solvent in step (b) is selected from group comprising of methanol, ethanol, isopropanol, n- propanol, n-butanol, iso butyl alcohol, tert-butyl alcohol, methoxyethanol, ethoxyethanol, pentanol, neo-pentyl alcohol, tert-pentyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, benzyl alcohol, phenol, glycerol, dimethylformamide (DMF), dimethylacetamide (DMAC), 1,3- dimethyl-3,4,5,6-tetrahydro-2(lH)-pyrimidinone (DMPU), l,3-dimethyl-2- imidazolidinone (DMI), N-methylpyrrolidinone (NMP), formamide, N- methylacetamide, N-methylformamide, acetonitrile, dimethylsulfoxide, propionitrile, ethyl formate, methyl acetate, hexachloroacetone, HMPA, HMPT, acetone, ethyl methyl ketone, ethyl acetate, isopropyl acetate, t-butyl acetate, sulfolane, N,N-dimethylpropionamide, nitromethane, nitrobenzene, tetrahydrofuran (THF), dioxane, water, polyethers or mixtures thereof. 7. A process as claimed in claim 6, wherein said polar solvent is selected from dimethylformamide and acetonitrile. 8. A process as claimed in claim 1 and 2, wherein said step (b) is optionally carried out in the presence of base selected from DBU, triethylamine and diisopropylethylamine 9. A process as claimed in claim 1 and 2, wherein said acid in step (c) is selected from organic or inorganic acid. 31 10. A process as claimed in claim 9, wherein said acid is selected from group comprising of hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid, perchloric acid or hydrofluoric acid. 11. A process as claimed in claim 1 and 2, wherein step (c) is carried out in a solvent selected from group comprising of water, polar organic solvents or mixtures thereof. 12. A process as claimed in claim 11, wherein said solvent is selected from group comprising of water, alcohol or mixtures thereof. 13. A process as claimed in claim 12, wherein said solvent is selected from group comprising of water, methanol, ethanol, isopropanol, n-propanol, tert-butanol, n-butanol or mixtures thereof. 14. A process as claimed in claim 1, wherein said oxidation in step (d) is carried out using Corey- Kim oxidation method, Dess- Martin reagent, Pfitzner Moffat method or modifications thereof or with dimethyl sulfoxide in presence of oxalyl chloride or phosphorous pentoxide or p-Toluene sulfonyl chloride or acetic anhydride or N-chlorosuccinimide or by manganese or chromium or selenium reagents, tert-amine oxides or any said oxidant in presence or absence of phase transfer catalyst. 15. A process as claimed in claim 1, wherein said alcohol in step (e) is selected from group comprising of methanol, ethanol, n-propanol, iso propanol, tert-butanol, n-butanol or mixtures thereof. 16. A process as claimed in claim 1, wherein step (e) is optionally carried out in the presence of mineral acid selected from hydrochloric acid, sulphuric acid or mixtures thereof. 17. A process as claimed in claim 2, wherein said alcohol in step (f) is selected from group comprising of methanol, ethanol, n-propanol, iso propanol, tert-butanol, n-butanol or mixtures thereof. 18. A process as claimed in claim 2, wherein step (f) is optionally carried out in the presence of mineral acid selected from hydrochloric acid, sulphuric acid or mixtures thereof. 32 wherein R is 19. A process as claimed in claim 2, wherein said oxidation in step (g) is carried out using Corey- Kim oxidation method, Des- Martins reagent, Pfitzner moffat method or modifications thereof or with dimethyl sulfoxide in presence of oxalyl chloride or phosphorous pentoxide or p-Toluene sulfonyl chloride or acetic anhydride or N-chlorosuccinimide. 20. The novel compounds of formula (XI), (XII) and (XIII) and R1 and R2 are same or different protecting groups selected from group comprising of substituted silyl group of formula -SiR3R4R5 (wherein R3, R4 and R5 are the same or different, and each is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, a phenyl substituted alkyl group in which the alkyl moiety has 1 to 3 carbon atoms, a phenyl group, a cycloalkyl group having 5 to 7 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, with the proviso that at least one of R3, R4 and R5 is other than hydrogen atom) 21. A process for the preparation of novel compounds of formula (XI), (XII) and (XIII) 33 wherein R is comprises steps of, (a) reacting compound of formula (IX) with carbonyldiimidazole in the presence of polar solvent and base to obtain compound of formula (X) wherein R1 and R2 are same or different protecting groups selected from group comprising of substituted silyl group of formula -SiR3R4R5 (wherein R3, R4 andR5 are the same or different, and each is a hydrogen atom, an alkyl group having 1 to 15 carbon atoms, a phenyl substituted alkyl group in which the alkyl moiety has 1 to 3 carbon atoms, a phenyl group, a cycloalkyl group 34 having 5 to 7 carbon atoms or an alkenyl group having 2 to 5 carbon atoms, with the proviso that at least one of R3, R4 and R5 is other than hydrogen atom) (b) condensing compound of formula (X) with R-NH2 in a suitable polar solvent to obtain compound of formula (XI) wherein R, R1 and R2 are same as defined hereinabove (c) treating compound formula (XI) with an acid to obtain compound of formula (XII) (d) oxidizing compound of formula (XII) in the presence of an oxidizing agent to form compound of formula (XIII). Dated this 12th day of July 2006. Abstract The present invention relates to the process for the preparation of compounds of formula (I) or its pharmaceutically acceptable salts wherein, R is 36