Synthesis of 1,3,4‐Oxadiazole Acyclo C‐Nucleosides Bearing 5‐Methylthio{7‐substituted‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}moieties

Abstract

AbstractOxidative cyclization of the sugar hydrazones (3a‐f) derived from {7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐ylsulfanyl}acetic acid hydrazide (1) and aldopentoses 2a‐c or aldohexoses 2d‐f with bromine in acetic acid in the presence of anhydrous sodium acetate, followed by acetylation with acetic anhydride gave the corresponding 2‐(per‐O‐acetyl‐alditol‐l‐yl)‐5‐methylthio{7H‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles (5a‐f). Condensative cyclization of the sugar hydrazones (3a‐f) by heating with acetic anhydride gave the corresponding 3‐acetyl‐2‐(per‐O‐acetyl‐alditol‐1‐yl)‐2,3‐dihydro‐5‐methylthio{7‐acetyl‐1,2,4‐triazolo[1,5‐d]tetrazol‐6‐yl}‐1,3,4‐oxadiazoles (11a‐f). De‐O‐acetylation of the acyclo C‐nucleoside peracetates (5 and 11) with methanolic ammonia afforded the hydrazono lactones (7) and the acyclo C‐nucleosides (12), respectively. The structures of new oxadiazole derivatives were confirmed by analytical and spectral data.