On Orthogonal and Selective Activation of Glycosyl Thioimidates and Thioglycosides: Application to Oligosaccharide Assembly
作者:Sophon Kaeothip、Alexei V. Demchenko
DOI:10.1021/jo201117s
日期:2011.9.16
Discrimination among S-thiazolinyl (STaz), S-benzoxazolyl (SBox), and S-ethyl anomeric leaving groups was achieved by fine-tuning activation conditions. Preferential glycosidation of a certain leaving group is determined neither by the strength of the activating reagent nor by the stability of the leaving group itself; instead, the type of activation plays the key role. The activation conditions established herein were applied to a sequential five-step synthesis of a hexasaccharide using six monosaccharide building blocks equipped with six different leaving groups.
Coordination chemistry approach to the long-standing challenge of stereocontrolled chemical glycosylation
作者:Papapida Pornsuriyasak、Cornelia Vetter、Sophon Kaeothip、Michael Kovermann、Jochen Balbach、Dirk Steinborn、Alexei V. Demchenko
DOI:10.1039/b903942b
日期:——
This study clearly demonstrates that a multi-dentate metal coordination to the leaving group, along with O-5 and/or a protecting group at O-6, has a strong effect on the stereoselectivity of chemical glycosylation.
A Novel Strategy for Oligosaccharide Synthesis via Temporarily Deactivated <i>S</i>-Thiazolyl Glycosides as Glycosyl Acceptors
作者:Papapida Pornsuriyasak、Umesh B. Gangadharmath、Nigam P. Rath、Alexei V. Demchenko
DOI:10.1021/ol048043y
日期:2004.11.1
activation of the S-thiazolyl (STaz) moiety of a glycosyl donor over the temporarily deactivated glycosylacceptor, bearing the same anomeric group, has been developed. This deactivation is achieved by engaging of the STaz moiety of the glycosylacceptor into a stable palladium(II) complex. Therefore, obtained disaccharides are then released from the complex by simple ligand exchange. [reaction: see text]