Aspects of stereochemistry. Part XXIV. The acid-catalysed rearrangement of 2,4-O-benzylidene-D-erythrose and 2,3-O-benzylidene-erythritol

Abstract

On treatment with toluene-p-sulphonic acid in dimethylformamide, 2,4-O-benzylidene-D-erythrose rearranges to 2,3-O-benzylidene-D-erythrofuranose with the phenyl group endo. The structure assigned to the rearranged product is proved, and a mechanism is presented which accounts for the stereospecificity. Under similar acid conditions, “cis”-2,3-O-benzylidene-erythritol rearranges into 1,3-O-benzylidene-DL-erythritol.