N-2-Glycosyl Thiosemicarbazides from N-3-Glycosyl Oxadiazolinethiones Obtained from 2-S-Glycosyl Oxadiazolines via Mild Thermal S→N Migration of the Glycosyl Moiety

A new class of N-2-glycosyl thiosemicarbazides has been synthesized from N-3-glycosyl oxadiazoline-thiones. Glycosylation of 5-(1H-indol-2-yl)-1,3,4-oxadiazolin-2(3H)-thione with acetylated α-glycosyl halides by grinding in the presence of basic alumina gave the S-glycosyl oxadiazoles while in the presence of Hg(II) chloride N-3 glycosyl analogues were obtained. In the presence of Et3N or K2CO3, mixtures of S- and N-glycosylated isomers were obtained as products. The S→N glycosyl migration under catalyst-free mild thermal conditions was described, and a new class of N-2-glycosyl thiosemicarbazides was synthesized from N-3-glycosyl oxadiazolinethiones by ring cleavage of the oxadiazolole ring by treatment with ammonia in methanol.