TRANSFORMATION OF D-ALLOSE AND L-GULOSE WITH POTASSIUM CYANATE INTO CYCLIC CARBAMATES

Treatment of D-allose and L-gulose with potassium cyanate in aqueous s olutions, buffered with sodium dihydrogen phosphate, gave cyclic carba mates (N,O-carbonyl derivatives) of the derived glycosylamines. D-Allo se gave the furanoid 1,2-cis-carbamate as a single product, but L-gulo se yielded a complex mixture of the furanoid 1,2-cis-carbamate, the py ranoid 1,2- and 1,3-cis-carbamates, and the furanoid 1,2-cis-carbamate of beta-L-ido configuration as a product of epimerization at C-2. The structures were derived from the NMR spectra of the free compounds an d those of their acetates. The structure of the main product in the re action of L-gulose, that of the pyranoid 1,2-cis-carbamate, was proved independently by X-ray structure determination of the tetra-acetate. The pyranoid ring was found to exist in the T-o(2)(L) conformation.