Carboxyl-mediated pictet-spengler reaction. Direct synthesis of 1,2,3,4-tetrahydro β-carbolines from tryptamine-2-carboxylic acids.

Abstract The Pictet-Spengler condensation of various tryptamine-2-carboxylic acids 1 with carbonyl compounds in benzene/dioxane/trifiuoroacetic acid (Table) with simultaneous loss of carbon dioxide, afforded directly the corresponding 1,2,3,4-tetrahydro β-carbolines 4 in good to excellent yields.