Synthesis of novel 2,'3'-unsaturated nucleoside

5'-tert-Butyldimethylsilyl-5-iodo-6-methyluridine 1 is converted to the bisxanthate 2 by reaction with carbon disulphide, followed by alkylation. The bisxanthate 2 on reduction with tri-n-butyltin hydride and desilylationaffords the unsaturated nucleoside, 2',3'-didehydro-2',3'-dideoxy-5-iodo-6-methyluridine 4.