Catalyst structure/enantioselectivity profiles for the asymmetric Strecker and Mannich reactions were obtained through systematic variation of each modular component of the catalyst. Although the thiourea derivative 1 afforded optimal results in both reactions (97-98% ee), the structural elements responsible for stereoinduction were found to be fundamentally different. Insights gleaned from these studies led to the development of a new generation catalyst for the Mannich reaction that promotes the asymmetric silyl ketene acetal addition to N-Boc benzaldimine in 94% ee. The new catalyst is a simple amino acid derivative possessesing less than half the molecular weight and two fewer stereocenters relative to 1.
通过系统地改变催化剂的每个模块成分,获得了不对称 Strecker 反应和 Mannich 反应的催化剂结构/对映体选择性曲线。虽然
硫脲衍
生物 1 在这两个反应中都能提供最佳结果(97-98% ee),但发现负责立体诱导的结构元素存在本质区别。从这些研究中获得的启示促成了新一代曼尼希反应催化剂的开发,该催化剂可促进 N-Boc
苯甲醛二胺的不对称
硅酮
缩醛加成反应,ee 值高达 94%。这种新型催化剂是一种简单的
氨基酸衍
生物,其分子量不到 1 的一半,立体中心也比 1 少两个。