Synthesis of tryptophans by alkylation of chiral glycine enolate equivalents with quaternary gramines

Abstract Quaternary gramines were found to be a suitable source of the 3-methylindole fragment for diastereoselective alkylation. The best yields and stereoselectivity were obtained for the alkylation of a chiral William’s morpholinone enolate. Based on this transformation, a general method for the synthesis of enantiopure, indole ring substituted tryptophan derivatives was developed with good overall yields.