Epoxidation of C-branched glycals: unexpected stereochemical results and their theoretical rationale
摘要:
This paper describes the synthesis of C-3 methyl-branched glycosides by epoxidation of partially unblocked L-configured glycals. The stereochemical result depends on the orientation of the allylic hydroxyl group. A theoretical explanation is presented, based on the conformational preferences of the respective glycal half-chair conformations that were estimated by applying the BP density functional and a valence triple-zeta basis set. (C) 2002 Elsevier Science Ltd. All rights reserved.
Noteworthy observations accompanying synthesis of the apoptolidin disaccharide
作者:Madduri Srinivasarao、Taesik Park、Yuzhong Chen、Philip L. Fuchs
DOI:10.1039/c1cc11448d
日期:——
A stereoselective synthesis of the apoptolidin disaccharide is reported. The key chemistry features a new transformation utilizing a highly selective tetramethylalkoxyalanate[v]-directed syn-methylation of a vinylogous ester, isolation of a hydrate of a 2-keto sugar, an eco-friendly radical cleavage of a bromomethyl group, and an efficient preparation of a fluorodisaccharide via the use of XtalFluor-E