Yasomanee Jagodige P, Parameswar Archana R, Pornsuriyasak Papapida, Rath Nigam P, Demchenko Alexei V
Department of Chemistry and Biochemistry, University of Missouri - St. Louis, One University Boulevard, St. Louis, Missouri 63121, USA.
Org Biomol Chem. 2016 Mar 21;14(11):3159-69. doi: 10.1039/c6ob00107f. Epub 2016 Feb 25.
2-O-Picolinyl protected glycosyl donors lead to the formation of 1,2-trans glycosides with complete stereoselectivity. This is due to the participatory effect of the picolinyl nitrogen that is able to block the bottom face of the ring via a six-membered cyclic intermediate. Herein we demonstrate that if the nitrogen atom of the O-picolinyl moiety is temporarily blocked by coordination to the metal center (Pd), it becomes unavailable to participate in glycosylation and hence the stereoselectivity of 2-O-picolinyl-assisted glycosylations can be "switched".
2-吡啶甲基保护的糖基供体能够以完全的立体选择性形成1,2-反式糖苷。这是由于吡啶甲基氮的参与效应，它能够通过六元环状中间体阻断环的底面。在此我们证明，如果O-吡啶甲基部分的氮原子通过与金属中心（钯）配位而暂时被阻断，它就无法参与糖基化反应，因此2-O-吡啶甲基辅助糖基化反应的立体选择性可以被“切换”。
