Starting from acetates 1 and propionates 6, TiCl4-mediated addition of their silyketene acetals 2 and 7 to aldehydes gave aldols 4 and 9, respectively, with high π-face and ‘anti’ differentiation (Schemes, and Tables 1 and 2). Alternation of the (E/Z)-enolate geometry led to reversed α- and β-inductions (7 9b, 8 10b). Non-destructive removal of the auxiliary yielded enantiomerically pure β -hydroxycarboxylic
从
乙酸盐1和
丙酸酯6开始,TiCl 4介导的将它们的
硅酮烯醇
缩醛2和7加到醛中,分别得到具有高π面和'抗'区分性的醇醛4和9(方案,以及表1和表2)。(E / Z)烯醇几何形状的交替导致相反的α和β诱导(7 9b,8 10b)。非破坏性去除辅助生成的对映体纯的β-羟基
羧酸13 。