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Abstract

Preparation of 2',3'-O-carbonyl derivatives of 5'-deoxy-6-azauridine and 6-azauridine using 1,1'-carbonyldiimidazole has been elaborated. 5'-Chloro and 5'-bromo derivatives were prepared by treatment of the 5'-O-mesyl derivative with quaternary ammonium halides, 5'-chloro derivatives also by direct halogenation with thionyl chloride in hexamethylphosphortriamide or with tetrachloromethane, triphenyl phosphine, and dimethylformamide. Derivatives of 5'-bromo-6-azauridine were reduced with tributyltin hydride to 5'-deoxy-6-azauridine compounds. 6-Azauridine 2',3'-carbonate (IVa) and its 5'-derivatives IVc and IVe on treatment with imidazole in dimethylformamide afforded 2,2'-anhydronucleosides IIIa-IIIc. The 2,2'-anhydro-5'-deoxy compound IIIc underwent alkaline hydrolysis to 5'-deoxy-1-β-D-arabino-pentofuranosyl-6-azauracil (VIa). Treatment of 2,2'-anhydro-5'-deoxy-5'-chloro derivative IIIb with hydrogen chloride led to 2',5'-dichloro derivative If.