An Efficient Method for Catalytic and Stereoselective Synthesis of 2-Deoxy-α-D-glucopyranosides from 3,4,6,-Tri-O-benzyl-2-deoxy-D-glucopyranose and Several Alcoholic Nucleophiles
Sterically Hindered 2,4,6-Tri-<i>tert</i>-butylpyridinium Salts as Single Hydrogen Bond Donors for Highly Stereoselective Glycosylation Reactions of Glycals
作者:Titli Ghosh、Ananya Mukherji、Pavan K. Kancharla
DOI:10.1021/acs.orglett.9b00626
日期:2019.5.17
We demonstrate here that the strained and bulky protonated 2,4,6-tri-tert-butylpyridine salts serve as efficient catalysts for highlystereoselectiveglycosylations of various glycals. Moreover, the mechanism of action involves an interesting single hydrogen bond mediated protonation of glycals and not via the generally conceived Brønsted acid pathway. The counteranions also play a role in the outcome
Direct elaboration of pent-4-enyl glycosides into disaccharides
作者:Bert Fraser-Reid、Peter Konradsson、David R. Mootoo、Uko Udodong
DOI:10.1039/c39880000823
日期:——
Pent-4-enylglycosides, on treatment with halonium ions, become chemospecifically activated so that coupling with partially protected monosaccharides can be effected, leading to the in situ formation of disaccharides.
Halogen-bond-assisted radical activation of glycosyl donors enables mild and stereoconvergent 1,2-cis-glycosylation
作者:Chen Zhang、Hao Zuo、Ga Young Lee、Yike Zou、Qiu-Di Dang、K. N. Houk、Dawen Niu
DOI:10.1038/s41557-022-00918-z
日期:2022.6
2-cis-glycosylation without using metals, strong (Lewis) acids, elaborate catalysts or labile substrates. Our method operates by a unique mechanism: it activates glycosyl donors through a radical cascade rather than the conventional acid-promoted, ionic process. As elucidated by computational and experimental studies, the allyl glycosyl sulfones (as donors) form halogen bond complexes with perfluoroalkyl iodides, which—merely