SYNTHETIC STUDIES ON (+)-HYDANTOCIDIN (3) - A NEW SYNTHETIC METHOD FOR CONSTRUCTION OF THE SPIRO-HYDANTOIN RING AT THE ANOMERIC POSITION OF D-RIBOFURANOSE

A facile synthetic route for the large-scale preparation of a herbicidal natural product, (+)-hydantocidin, is described. The protected D-psicose 6, prepared in five steps from D-fructose, was stereospecifically converted to azido-amide 14 by N-glycosidation (TMSN3/TMSOTf), oxidation and amination. Hydantoin ring-construction on 14 was achieved by aza-Wittig reaction (PBu3/CO2/CH3CN) to give 16 without epimerization at the anomeric center. After acetylation, stepwise deprotection of 24 afforded (+)-hydantocidin 1 in 16% overall yield from D-fructose.