Direct, stereoselective thioglycosylation enabled by an organophotoredox radical strategy
作者:Peng Ji、Yueteng Zhang、Feng Gao、Fangchao Bi、Wei Wang
DOI:10.1039/d0sc04136j
日期:——
transfer pathway have dictated glycosylation development, the direct glycosylation of readily accessible glycosyl donors as radical precursors is particularly appealing because of high radical anomeric selectivity and atom- and step-economy. However, the development of the radical process has been challenging owing to notorious competing reduction, elimination and/or SN side reactions of commonly used
虽然涉及 2e -转移途径的策略决定了糖基化的发展,但由于自由基异头选择性高以及原子和步骤经济性,易于获得的糖基供体作为自由基前体的直接糖基化特别有吸引力。然而,由于常用的不稳定糖基供体的竞争性还原、消除和/或 S N副反应,自由基过程的发展一直充满挑战。在这里,我们介绍了一种有机光催化策略,通过光氧化还原介导的 HAT 催化,糖基溴可以有效地转化为相应的异头自由基,无需过渡金属或导向基团,并实现高度异头选择性。温和的反应条件能够合成具有挑战性的α-1,2-顺式硫代糖苷、各种官能团的耐受性以及常见戊糖和己糖的广泛底物范围,证明了该平台的强大功能。此外,这种通用方法与 sp 2和 sp 3硫亲电子试剂以及总共探测的 50 种底物的后期糖基多样化兼容。
Streamlined Iterative Assembly of Thio‐Oligosaccharides by Aqueous
<i>S</i>
‐Glycosylation of Diverse Deoxythio Sugars
作者:Peng Wen、Peijing Jia、Qiuhua Fan、Bethany J. McCarty、Weiping Tang
DOI:10.1002/cssc.202102483
日期:2022.2.8
Step by step: A streamlined practical iterative synthesis of S-oligosaccharides is developed in aqueous solution without the need of protecting any of the hydroxy groups. Various deoxythio sugar building blocks can be prepared efficiently. The Ca(OH)2-promoted aqueous S-glycosylation can be realized with high chemo- and stereoselectivity.
Hydrogensulfide reacted with D-glucose in hydrogen fluoride solution to yield preponderantly alpha,alpha-1-thiotrehalose, beta,beta-1-thiotrehalose, and the alpha,beta anomer. Conditions were found under which the thiotrehaloses were obtained in the respective proportions of 8:5:5.