Synthesis of novel unsaturated purine nucleoside

5'-Silylated derivative of N 6 -n-propyladenosine 1 has been converted to bisxanthate 2 by reaction with CS 2 followed by alkylation.The bisxanthate affords 2', 3'-didehydro-2', 3'-dideoxy-N 6 -n-propyladenosine 4 on reduction with tri-n-butyltin hydride and desilylation.