Carbon tetrachloride-free allylic halogenation-mediated glycosylations of allyl glycosides

Abstract

The allylic bromination of allyl glycosides is conducted using NBS/AIBN reagents in (EtO)₂CO and PhCF₃ solutions, without using CCl₄ as a solvent. The activated mixed halo-allyl glycosides led to glycosylations, mediated by a triflate, in a latent-active manner, with the allyl glycosides acting as donors and acceptors. Systematic glycosylation studies are performed with different triflate promoters, non-glycosyl acceptors and various allyl glycosyl donors. One-pot allylic halogenations and subsequent glycosylations are developed in PhCF₃ solutions. This newer glycosylation method is utilized to obtain xylo-pyranoside di- and trisaccharides.