Fragmentation of carbohydrate anomeric alkoxyl radicals: synthesis of chiral 1-bromo-1-fluoro-1-iodo-alditols

The reaction of 2-bromo-2-deoxy-2-fluoro-hexopyranose and -pentopyranose compounds from the -gluco, -galacto, -rhamno, -fuco, and -arabino carbohydrate series with (diacetoxyiodo)benzene and iodine, under visible light irradiation conditions, generated the corresponding 1-bromo-1-deoxy-1-fluoro-1-iodo-alditols with one less carbon. In the case of the -galacto derivative, the diastereoisomeric mixture can be chromatographically separated and the absolute configuration determined by X-ray crystallographic analysis of the (1R)-isomer.