Cyclization of 1,2:3,4-di-O-isopropylidene-α-D-galacto-1,6-hexodialdo-1,5-pyranose acylhydrazone and semicarbazone

Abstract

Cyclization of 1,2:3,4-di-O-isopropylidene-α-D-galacto-1,6-hexodialdo-1,5-pyranose benzoylhydrazone using acetylating mixtures led us to the corresponding (2R)- and (2S)-5- phenyl-1,3,4-oxadiazoline derivatives. The same conditions applied to the semicarbazone produced the 5-methyl-1,3,4-oxadiazoline derivative as the main compound, which is formed with acetylating mixtures even at room temperature. X-Ray analysis and NMR techniques were used to determine the stereochemistry of the new asymmetric centers.