Studies on the chemistry of sodium nitronates and nitronic esters derived from 5-glyco-4-nitro-1-cyclohexenes

Reactions of sodium nitronates derived from 5-glyco-4-nitro-1-cyclohexenes with d-galacto or d-manno sugar side-chains have been investigated. With acetic anhydride/pyridine, these salts suffered an intramolecular cyclization affording high yields of tetraacetylated isoxazoline N-oxides. Treatment of the latter compounds with sodium methoxide yielded, either the corresponding deacetylated derivative or a bicyclic oxime, depending on the configuration of the sugar side-chain. Furthermore, unstable nitronic acid has been isolated by recrystallization of nitronate in dimethylsulfoxide, as well as by reaction of this substance with cold aqueous sulfuric acid. By refluxing with trimethyl phosphite, the N-oxides and led to isoxazolines which, like their precursors, could be considered as acyclic C-nucleosides.