Stereoselective synthesis of α-glucosides by neighbouring group participation via an intermediate thiophenium ion

The use of a 2-O-(thiophen-2-yl)methyl protecting group allows highly stereoselective alpha-glucosylation of a trichloroacetimidate donor: increased stereoselectivity, presumably arising from the intramolecular formation of a transient intermediate thiophenium ion, correlates with increased bulk of the glycosyl acceptor. (C) 2009 Elsevier Ltd. All rights reserved.