A new synthesis of 5'-deoxy-8,5'-cyclo-adenosine and -inosine: conformationally-fixed purine nucleosides (nucleosides and nucleotides. XVI).

A versatile method for the synthesis of 5'-deoxy-8,5'-cycloadenosine, a conformationally-fixed "anti" type of adenosine, was presented. Irradiation of 2', 3'-O-isopropylidene-5'-deoxy-5'-phenylthioadenosine with 60W Hg vapor lamp afforded 2',3'-O-isopropylidene-5'-deoxy-8,5'-cycloadenosine in high yield. The use of other 5'-alkylthio derivatives also gave the cycloadenosine, though the yields were rather poor. Deacetonation of the cyclocompound with 0.1N HCl gave 5'-deoxy-8,5'-cycloadenosine. The cycloinosine derivative was similarly prepared. The nmr, mass and CD spectra of 5'-deoxy-8,5'-cycloadenosine were given and discussed with the previously reported results.