Chemical studies on carbohydrates (III). The ring conversion of hydrazinoaldoses into pseudo‐N‐nucleosides by ring transformation

Abstract

AbstractOn reacting 3‐deoxy‐3‐hydrazino‐1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐allofuranose (2) or 3‐deoxy‐3‐hydrazino‐1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (8) with N‐methylpyrimidinium methyl sulfate (4) at room temperature, formation of 3‐deoxy‐3‐N‐pyrazolyl‐1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐allofuranose (3) and 3‐deoxy‐3‐N‐pyrazolyl‐1,2: 5,6‐di‐O‐isopropylidene‐α‐D‐glucofuranose (9), respectively, takes place. This ring transformation has been explained by an ANRORC mechanism. Similarly, 6‐deoxy‐6‐hydrazino‐1,2‐O‐isopropylidene‐α‐D‐glucofuranose (10) and methyl‐4,6‐O‐benzylidene‐2‐deoxy‐2‐hydrazino‐α‐D‐mannopyranoside (11) react with the pyrimidinium salt to give the corresponding pyrazolylaldoses.Starting from 3,6‐anhydro‐5‐deoxy‐5‐hydrazino‐1,2‐O‐isopropylidene‐β‐L‐idofuranose (16), in addition to the expected 3,6‐anhydro‐5‐deoxy‐5‐N‐pyrazolyl‐1,2‐O‐isopropylidene‐β‐L‐idofuranose (17a), 3,6‐anhydro‐5‐deoxy‐5‐(1,2,4‐triazol‐1‐yl)‐1,2‐O‐isopropylidene‐β‐L‐idofuranose (17b) is formed. The same conversion of substituted hydrazines into pyrazolyl and triazolyl derivatives is observed in the reaction of 1‐deoxy‐1‐hydrazino‐2,3‐O‐isopopylidene‐D‐ribofuranose (12) with the pyrimidinium salt. This pyrimidine‐to‐triazole ring transformation can also be explained by an ANRORC mechanism.Further investigation of the reactivity of hydrazinoaldoses towards other positively charged azines shows the general scope of this reaction.