Tritylsulfenyl- and 2-nitrophenylsulfenyl-substituted glyoxyl imines were used in chiral phosphoric acid catalyzed Friedel-Crafts (FC) reactions with indole. High yields and ee values ranging from 86% for Nps-protected (S)-indolylglycine to 88% for Trs-protected (R)-indolylglycine were obtained. On a preparative scale, a FC product with 99.5% ee and 71% yield was readily obtained by crystallization
Tritylsulfenyl-和2-nitrophenylsulfenyl-取代的
乙醛亚胺用于手性
磷酸催化的与
吲哚的Friedel-Crafts (FC)反应。获得了高产率和 ee 值,范围从 Nps 保护的 (S)-
吲哚甘
氨酸的 86% 到 Trs 保护的 (R)-
吲哚甘
氨酸的 88%。在制备规模上,通过反应混合物的结晶很容易获得具有 99.5% ee 和 71% 产率的 FC 产品。在温和的酸性条件下去除 Nps 保护基不会影响 α-碳原子的立体
化学完整性,并且以 >= 98% ee 提供 (S)-
吲哚甘
氨酸。