The additions of 2-(trimethylsiloxy)furan (5) and 2-(tert-butyldimethylsiloxy) -3-methylfuran (6) to the cyclic N-acyliminium ion generated upon treatment of 1-benzyloxycarbonyl-2-ethoxypyrrolidine (7) with diethyl ether-boron trifluoride complex afforded mixtures of adducts threo-8/erythro-8 and threo-9/erythro-9, respectively, in which the threo diastereoisomers dominated by ratios of 8.5-6:1.
将2-(三甲基
硅氧基)
呋喃(5)和2-(叔丁基二甲基
硅氧基)-
3-甲基呋喃(6)加入到通过将1-苄氧基羧酰基-2-乙氧基
吡咯烷(7)与二
乙醚-
三氟化硼复合物反应生成的循环N-
酰亚胺阳离子中,分别获得了高达8.5-6:1比例的threo-8/erythro-8和threo-9/erythro-9的加成物混合物,其中threo对映异构体占主导地位。