Synthesis of Glycosyl Chlorides and Bromides by Chelation Assisted Activation of Picolinic Esters under Mild Neutral Conditions
作者:Peng Wen、Christopher J. Simmons、Zhi-xiong Ma、Stephanie A. Blaszczyk、Paul G. Balzer、Wenjing Ye、Xiyan Duan、Hao-Yuan Wang、Dan Yin、Christopher M. Stevens、Weiping Tang
DOI:10.1021/acs.orglett.0c00078
日期:2020.2.21
formation of glycosyl chlorides and bromides from picolinic esters undermild and neutral conditions. Benchtop stable picolinic esters are activated by a copper(II) halide species to afford the corresponding products in high yields with a traceless leaving group. Rare β glycosyl chlorides are accessible via this route through neighboring group participation. Additionally, glycosyl chlorides with labile protecting
Stereocontrolled chemical glycosylation remains a major challenge despite vast efforts reported over many decades and so far still mainly relies on trial and error. Now it is shown that the relative reactivity value (RRV) of thioglycosides is an indicator for revealing stereoselectivities according to four types of acceptors. Mechanistic studies show that the reaction is dominated by two distinct intermediates:
A mild and general method for preparation of α-glycosyl chlorides
作者:Chih-Wei Chang、Shih-Sheng Chang、Chin-Sheng Chao、Kwok-Kong T. Mong
DOI:10.1016/j.tetlet.2009.05.077
日期:2009.8
A mild and efficient chlorination method for production of glycosyl chlorides is first described which employs inexpensive trichlorotriazine (TCT) and DMF as a chlorination reagent and is compatible with typical acid-labile hydroxyl protecting functions. The scope and limitations, reaction mechanism and its application in the sequential glycosylations are discussed. (C) 2009 Elsevier Ltd. All rights reserved.