Enantioselective Copper(II)/Box‐Catalyzed Synthesis of Chiral β3‐Tryptophan Derivatives

Abstract

Abstractβ‐Amino acids and their derivatives are important building blocks for the preparation of various bioactive compounds and materials. We developed a highly efficient method for the synthesis of β3‐tryptophan derivatives based on enantioselective Friedel‐Crafts alkylation of indoles with phthaloyl‐protected aminomethylenemalonate in the presence of chiral complex as a catalyst. A wide range of indoles with electron‐donating and electron‐withdrawing substituents gave the desired products in high yields (up to 99 %) and excellent enantioselectivities (up to 99 % ee). In the case of pyrrole the Friedel‐Crafts product was obtained in up to 90 % yield and up to 82 % ee.