Synthesis of guanosine and its derivatives from AICA‐riboside

Abstract A novel and convenient method for the synthesis of guanosine is described. The reaction of AICA‐riboside with sodium methylxanthate gave 2‐mercaptoinosine in almost quantitative yield. The latter was oxidized with hydrogen peroxide to afford inosine‐2‐sulfonic acids, which was readily animated to give guanosine in excellent yield. Similarly, the preparation of N 2 ‐methylguanosine and N 2 , N 2 ‐dimethylguanosine, minor constituents of transfer RNA, was also accomplished. Furthermore, this procedure was extended to the synthesis of 2′,3′‐ O ‐isopropylideneguanosine and the isopropylidene derivatives of various N 2 ‐substituted guanosines from 2′,3′‐ O ‐isopropylidene‐AICA‐riboside. Guanosine via 2′,3′‐ O ‐isopropylideneguanosine was successfully phosphorylated to give 5′‐guanylic acid.