Patent ID: 7632940

Claim:
A process for the preparation of 4′-azido-cytidine (I) or of a pharmaceutically accepted salt thereof, comprising the steps of: a) contacting a 4′-azido-nucleoside of the formula II wherein: R 1 and R 2 are independently selected from COR 4 and C(═O)OR 4 or R 1 and R 2 together form a —CH 2 —, —C(CH 3 ) 2 —, —CH-phenyl- or —CH(OMe)- a bridge; R 3 is selected from COR 4 and C(═O)OR 4 and R 4 is independently C 1-12 -alkyl, phenyl optionally substituted with 1 to 3 substituents selected from the group consisting of C 1-6 -alkyl, C 1-6 -alkoxy, halogen, nitro or cyano; with imidazole, phosphorous oxychloride and triethylamine, optionally in the presence of a first organic solvent, to form an imidazole compound of formula IIIa wherein R 1 , R 2 and R 3 are as above; b) contacting the compound of formula IIIa with aqueous ammonia and a second organic solvent to form an amine of formula IIIb; wherein R 1 , R 2 and R 3 are as above; and, c) deprotecting the amine of formula IIIb to afford 4′-azido-cytidine (I).