Glycosyl fluorides have been found to be important intermediates in glycosylations using trichloroacetimidate donors and BF3∙OEt2 activation (0.2-1 equiv.). Low temperature NMR revealed that the a-trichloroacetimidate was transformed into the glycosyl fluoride with inversion of stereochemistry, whereas the b-anomer was not. A concerted mechanism has been suggested for the stereospecific formation of
已发现糖基
氟是使用三
氯乙
酰亚胺供体和
BF3∙OEt2 活化(0.2-1 当量)进行糖基化的重要中间体。低温 NMR 显示 a-三
氯乙
酰亚胺酯通过立体
化学反转转化为糖基
氟,而 b-端基异构体则不然。已经提出了糖基
氟的立体有择形成的协调机制,这在经典机制中没有得到解释。