Reaction between 2′,3′,5′-tri-O-acetyladenosine and aryl chloroformates. 2′,3′,5′-Tri-O-acetyl-N(6)-phenoxycarbonyladenosine as an intermediate in the synthesis of 6-ureidopurine ribosides

Abstract

Reaction between 2′,3′,5′-tri-O-acetyladenosine (6) and p-nitrophenyl chloroformate in pyridine solution at 20 °C or between (6) and phenyl chloroformate in pyridine solution at 70 °C gives the protected symmetrical urea derivative (7b) in moderate or high yield. Deacetylation of (7b) gives the corresponding unprotected urea (7a). Treatment of (6) with an excess of phenyl chloroformate in pyridine solution at 20 °C gives the bisphenoxycarbonyl derivative (10) which, on reaction with morpholine in dioxan solution, is rapidly converted into 2′,3′,5′-tri-O-acetyl-N(6)-phenoxycarbonyladenosine (3c). Compound (3c) readily reacts with cyclohexylamine, ammonia, and glycine methyl ester at 20 °C to give, after deacetylation, the corresponding 6-ureidopurine riboside derivatives (9b, c, and d; R¹= H) in high yields.