Selective activation of “armed’ and ‘'disarmed” glycaldonors enabling the stereo-controlled glycosylations by employing Cu(II)-catalyst as the promoter has been realized. The distinctive stereochemical outcome in the process is mainly influenced by the presence of diverse protecting groups on the donor and the solvent system employed. The protocol is compatible with a variety of aglycones including
(Aka) to quantify the nucleophilicity of hydroxyl groups in glycosylation influenced by the steric, electronic and structural effects, providing a connection between experiments and computer algorithms. The subtle reactivity differences among the hydroxyl groups on various carbohydrate molecules can be defined by Aka, which is easily accessible by a simple and convenient automation system to assure
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 new organocatalyticglycosylation method based on electron‐deficient pyridiniumsalts is reported. At ambient temperature and catalyst loadings as low as 1 mol %, 2‐deoxyglycosides were formed from benzyl‐ and silyl‐protected glycals and primary or secondary glycosyl acceptors, with excellent yields and anomeric selectivity. Mechanistic investigations point to alcohol–pyridinium conjugates (1,2‐addition
Stereoselective Electro‐2‐deoxyglycosylation from Glycals
作者:Miao Liu、Kai‐Meng Liu、De‐Cai Xiong、Hanyu Zhang、Tian Li、Bohan Li、Xianjin Qin、Jinhe Bai、Xin‐Shan Ye
DOI:10.1002/anie.202006115
日期:2020.8.24
report a novel and highly stereoselective electro‐2‐deoxyglycosylation from glycals. This method features excellent stereoselectivity, scope, and functional‐group tolerance. This process can also be applied to the modification of a wide range of natural products and drugs. Furthermore, a scalable synthesis of glycosylated podophyllotoxin and a one‐pot trisaccharide synthesis through iterative electroglycosylations