Total Synthesis and Structural Revision of Rebaudioside S, a Steviol Glycoside
作者:Guo-En Wen、Hui Liu、Qi-Shuang Yin、Jin-Xi Liao、Yuan-Hong Tu、Qing-Ju Zhang、Jian-Song Sun
DOI:10.1021/acs.joc.0c00442
日期:2020.12.18
considerable challenges in stereoselectivitycontrol. Through systematic investigations, the effect of the internal glycosidic linkage configuration on the glycosylation stereoselectivity of 1,2-linked disaccharide donors was disclosed, and the intensified solvent effect by the 4,6-O-benzylidene protecting group was also observed with glucosyl donors. Through the orchestrated application of these favorable
TolSCl/AgOTf catalysis system and the remote participation effect or steric β-shielding of functionalizedgroups at the donor 6-O-position. Low substrate concentration was revealed to favor the α-stereochemical outcome of glycosylations between bulkier building blocks. The synthetic approach established here would be very useful for the preparation of more complex α-glucans containing different types
Convergent Synthesis of the Hexasaccharide Repeating Unit of the<i>O</i>-Antigenic OPS of<i>Escherichia coli</i>O133
作者:Ankita Mitra、Balaram Mukhopadhyay
DOI:10.1002/ejoc.201900815
日期:2019.8.15
Synthesis of the hexasaccharide repeatingunit of the O-antigen from E. coli O133 has been accomplished with rational protecting group manipulations on commercially available monosaccharides and stereoselective glycosylations through a convergent protocol. A late stage TEMPO mediated oxidation is used to install the required uronic acid moiety. Chloroacetate group is used extensively as a temporary
来自大肠杆菌 O133 的 O-抗原的六糖重复单元的合成是通过对市售单糖和立体选择性糖基化的合理保护基操作通过收敛协议完成的。后期 TEMPO 介导的氧化用于安装所需的糖醛酸部分。氯乙酸酯基团被广泛用作临时保护基团。
Exploring the Dual Functions of Distal Acyl Group Direction in Various Nucleophilic Environments