Face-selective conjugate addition of lithiated Schöllkopf's bislactim ether derived from cyclo[Ala-d-Val] 4 to prochiral vinylphosphonates 5a-c allows a direct and stereocontrolled access to optically pure MAP4 analogues, the 2-amino-2-methyl-4-phosphonobutanoic acid derivatives 12-15. The relative stereochemistry was assigned from NMR studies of the cyclic derivatives 16 and 17. Eight-membered transition states are invoked to rationalize the stereochemical outcome of the additions.
                                    将环[Ala-d-Val] 4 衍生的石化 Schöllkopf 双内酰胺醚与亲手性
乙烯基膦酸盐 5a-c 进行面选择性共轭加成,可以直接立体控制地获得光学纯度为 
MAP4 的类似物,即 2-
氨基-2-甲基-4-
膦酸丁酸衍
生物 12-15。环状衍
生物 16 和 17 的核磁共振研究确定了其相对立体
化学性质。八元过渡态被用来合理解释加成的立体
化学结果。