More than a Leaving Group: N ‐Phenyltrifluoroacetimidate as a Remote Directing Group for Highly α‐Selective 1,2‐ cis Glycosylation

Autor: Xianglai Liu, Yingying Song, Ao Liu, Yueer Zhou, Qian Zhu, Yetong Lin, Huiyong Sun, Kaidi Zhu, Wei Liu, Ning Ding, Weijia Xie, Haopeng Sun, Biao Yu, Peng Xu, Wei Li
Rok vydání: 2022
Předmět:
Zdroj: Angewandte Chemie International Edition. 61
ISSN: 1521-3773
1433-7851
Popis: The anomeric configuration can greatly affect the biological functions and activities of carbohydrates. Herein, we report that N-phenyltrifluoroacetimidoyl (PTFAI), a well-known leaving group for catalytic glycosylation, can act as a stereodirecting group for the challenging 1,2-cis α-glycosylation. Utilizing rapidly accessible 1,6-di-OPTFAI glycosyl donors, TMSOTf-catalyzed glycosylation occurred with excellent α-selectivity and broad substrate scope, and the remaining 6-OPTFAI group can be cleaved chemoselectively. The remote participation of 6-OPTFAI is supported by the first characterization of the crucial 1,6-bridged bicyclic oxazepinium ion intermediates by low-temperature NMR spectroscopy. These cations were found to be relatively stable and mainly responsible for the present stereoselectivities. Further application is highlighted in glycosylation reactions toward trisaccharide heparins as well as the convergent synthesis of chacotriose derivatives using a bulky 2,4-di-O-glycosylated donor.
Databáze: OpenAIRE
Externí odkaz: