Synthesis of C-2 Methylene Glycosides by AuCl₃ Catalysis

Significance

Prior to this study several methods for the preparation of C-2 methylene glycosides had been reported. These include Ferrier reaction using BF₃×Et₂O or InCl₃ as well as similar strategies using Nafion-H, Montmorillonite K-10, and Pd(PPh₃)₄. The present paper utilizes the propargyloxy group as a leaving group in the presence of catalytic AuCl₃ to effect S_N2′ addition of various functionalized aglycones to propargyloxy­methyl glycals. C-2 Methylene glycosides are obtained in moderate yields with stereoselective formation of the α-glycoside.