Regenerative Glycosylation under Nucleophilic Catalysis
摘要:
This article describes 3,3-difluoroxindole (HOFox)-mediated glycosylation. The uniqueness of this approach is that both the in situ synthesis of 3,3-difluoro-3H-indol-2-yl (OFox) glycosyl donors and activation thereof can be conducted in a regenerative fashion as is a typical reaction performed under nucleophilic catalysis. Only a catalytic amount of the OFox imidate donor and a Lewis acid activator are present in the reaction medium. The OFox imidate donor is constantly regenerated upon its consumption until glycosyl acceptor has reacted.
立体选择性β-甘露糖基化是寡糖合成中最具挑战性的问题之一。在此,报道了使用廉价的草酰氯、氧化膦和 LiI 进行一锅氯化、碘化、糖基化序列后,从糖基半缩醛中高度选择性地合成 β-甘露糖苷和 β-鼠李糖苷。本协议适用于广泛的糖基受体和武装糖基供体。该方法不需要构象限制的供体或导向基团;建议观察到的高β-选择性是通过碘化锂促进的 α-糖基碘化物的 S N 2 型反应实现的。