Sels d'alkyloxyphosphonium—XVI: Activation de l'hydroxyle anomere des 2,3,4,6 tetra-o-acyl-d-mannopyranoses

The joint action of tris(dimethylamino)phosphine-carbon tetrachloride on a tetra-O-acyl-2,3,4,6-d-mannopyranose leads to one α anomeric oxyphosphonium chloride (ATDP salt). This salt is not isolable, but decomposes to yield an anomeric mixture of 1-chloro derivatives. The reaction with alcohols give rise to the formation of orthoesters while thiophenol reacts to yield only the β-thiomannoside. These results are discussed and interpreted.