5'-O-Acetyl-8-bromo-2', 3'-O-isopropylideneadenosine was obtained either by bromination of 5'-O-acetyl-2', 3'-O-isopropylideneadenosine with N-bromoacetamide or by bromination of 2', 3'-O-isoropylideneadenosine followed by acetylation. 5'-O-Acetyl-8-bromoadenosine, obtained by the formic acid hydrolysis of the isopropylidene group, was tosylated to afford 2'-tosyl-, 3'-tosyl- and 2', 3'-di-O-tosyl-5'-O-acetyl-8-bromoadenosine. Reaction of these tosylates with thiourea followed by deacetylation gave 8, 2'-anhydro-8-mercapto-9-β-D-arabinofuranosyladenine, 8, 3'-anhydro-8-mercapto-9-β-D-xylofuranosyladenine and 8, 2'-anhydro-8-mercapto-3'-O-tosyl-9-β-D-arabinosyladenine, respectively. Desulfurization of 8, 2'-and 8, 3'-anhydro derivatives gave 2'-deoxy- and 3'-deoxyadenosine (Cordycepin).