title: Hydrogen-bond-mediated aglycone delivery (HAD): a highly stereoselective synthesis of 1,2-cis α-D-glucosides from common glycosyl donors in the presence of bromine.
abstract: Described herein is the expansion of the picoloyl protecting-group assisted H-bond mediated aglycone delivery (HAD) method recently introduced by our laboratory. At first it was noticed that high α-stereoselectivity is only obtained with S-ethyl glycosyl donors and only in the presence of dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST), in high dilution, and low temperature. Combining the mechanistic studies of the HAD reaction and bromine-promoted glycosylations allowed a very effective method to be devised that allows for highly stereoselective α-glycosidation of practically all common leaving groups (S-phenyl, S-tolyl, S/O-imidates) at regular concentrations and ambient temperature.
authors.affiliation: Department of Chemistry and Biochemistry, University of Missouri-St. Louis, One University Boulevard, St. Louis, MO 63121 (USA).
authors.forename: Jagodige P
authors.initials: JP
authors.lastname: Yasomanee
authors.forename: Alexei V
authors.initials: AV
authors.lastname: Demchenko
keywords: aglycone delivery; carbohydrates; glycosylation; leaving group; stereocontrol