Abstract On hydrazinolysis in 1: 4 acetic acid-pyridine, and in pyridine, partial O-deacylation of fully acylated methyl glycosides and some other glycosyl compounds (23 compounds) was found to be induced, to give, in good yields, products bearing one free hydroxyl group; the results obtained indicated that, among the primary and secondary O-acyl groups, the 2-O- acyl groups were, in general, the most labile toward the nucleophile (hydrazine). ...