C2‐Cyanomethyl (CNMe) Ether‐Protected Glycosyl Trichloroacetimidate Donors for Stereoselective β‐O‐Glycosylations

Abstract

Stereoselective construction of glycosidic linkages have emerged as one of the pivotal aspects for the synthesis of complex oligosaccharide assemblies. We herein report C2cyanomethyl (CNMe) ether as a strong stereodirecting group on trichloroacetimidate glycosyl donors for the synthesis of 1,2trans-β-O-glycosides. The developed donors bearing various arming and disarming protections along with C2-CNMe ether delivered the glycosides in short reaction time, moderate to good yields and high to excellent stereoselectivities. Gluco-and galacto-configured donors were found compatible with an array of alcohols having varied reactivities. The orthogonality of the CNMe ether protection with silyl ether group has been further explored for sequential glycosylations.