Novel chemoselective tosylation of the alcoholic hydroxyl group of syn-(alpha),(beta)-disubstituted (beta)-hydroxy carboxylic acids

(beta)-Hydroxy acids were readily converted into (beta)-tosyloxy acids (hydroxyl group activation) in moderate to excellent yields via the O,O-dianions generated by treatment with methyllithium and thus make it possible to prepare anti(alpha),(beta)-disubstituted (beta)lactones directly from the syn aldols.