The acetylation of 5'-deoxy-5-fluorocytidine (I) with acetic anhydride in dry pyridine gives 2',3'-di-O-acetyl-5'-deoxy-5-fluorocytidine (II), which is condensed with pentyl chloroformate (III) by means of pyridine in dichromethane yielding 2',3'-di-O-acetyl-5'-deoxy-5-fluoro-N4-(pentyloxycarbonyl)cytidine (IV). Finally, this compound is deacetylated with NaOH in dichloromethane/water. The diacetylated cytidine (II) can also be obtained by condensation of 5-fluorocytosine (V) with 1,2,3-tri-O-acetyl-5-deoxy-beta-D-ribofuranose (VI) by means of trimethylchlorosilane in acetonitrile or HMDS and SnCl4 in dichloromethane..