合成路线1

Reaction of L-arabinose (XIII) with cyanamide (XIV) in aqueous methanolic ammonia gives the oxazolidine derivative (XV), which is cyclized with methyl propynoate (XVI) in refluxing ethanol to yield the anhydro uridine (XVII). Acylation of both OH groups of (XVII) by means of benzoyl cyanide (XVIII) in DMF affords the dibenzoate (XIX), which is treated with anhydrous HCl in DMF to provide the chloro uridine derivative (XX) or with HI in DMF or LiI and BH3/Et2O in DMF to provide the iodo uridine (XXI). Dehalogenation of (XX) or (XXI) by means of tri-butyltin hydride in refluxing benzene furnishes 3',5'-di-O-benzoyl-2'-deoxy-b-L-uridine (XXII). The trans-glycosylation of (XXII) with bis(trimethylsilyl)-5-fluorouracil (XXIII) by means of TMS-OTf in acetonitrile gives the corresponding 5-fluoro-L-uridine derivative (XXIV) as a mixture of the a- and b-anomers that is separated by chromatography. Debenzoylation of (XXIV) with ammonia in methanol yields 2'-deoxy-b-L-uridine (XXV), which is treated with MsCl and pyridine to afford the dimesylate (XXVI). Reaction of compound (XXVI) with NaOH in methanol/water provides the unstable intermediate (XXVII) that rearranges to the cyclic ether (XXVIII). Treatment of (XXVIII) with 1,2,4-triazole (XXIX) and p-chlorophenyl dichlorophosphate in pyridine provides the adduct (XXX), which by cleavage of the triazole ring by means of NH4OH in dioxane gives the corresponding cytidine derivative (XXXI). Finally, this compound is treated with potassium tert-butoxide in DMSO.