N-Fluorenyltryptamines as a Useful Platform for Catalytic Enantio­selective Pictet–Spengler Reactions

Abstract In the presence of a thiourea–carboxylic acid catalyst, N -9-fluorenyltryptamines undergo highly enantioselective Pictet–Spengler reactions with a range of aldehydes. The reaction works particularly well with aromatic aldehydes, tolerating electronically diverse substituents in all ring positions. Electron-deficient tryptamines are viable substrates. Removal of the fluorenyl protecting group is readily accomplished without deterioration of product ee.