Regio and Stereoselective One-Pot Synthesis of 2-Deoxy-3-thio Pyranoses and Their O-Glycosides from Glycals

A reaction of glycals with two different types of nucleophiles in the presence of SnCl4 enabled one-pot rapid access to 2-deoxy-3-thio pyranoses and their O-glycosides. The process involves thioaryl substitution at C-3 with stereoretention and alpha- selective O-glycosylation at C-1 from D-glycals, thus combining two reactions with three interventions. The present methodology features an attractive three-component coupling (1:1.2:1.5 ratio) with operational simplicity at 0 degrees C in 10-20 min. This stereoselective one-pot 1,3-difunctionalization approach of glycals is compatible with wide range of primary and secondary alcohols affording products in good to excellent yields. This methodology was successfully extended toward disaccharide synthesis. Several control experiments suggested a plausible reaction mechanism and rationale behind regio and stereoselectivity. The reaction strategy possesses an intrinsic ability for the synthesis of various natural products and drug molecules.