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Enantioselective BINOL-Phosphoric Acid Catalyzed Pictet−Spengler Reactions of N -Benzyltryptamine

2008; American Chemical Society; Volume: 73; Issue: 16 Linguagem: Inglês

10.1021/jo8010478

1520-6904

Nishant V. Sewgobind, Martin J. Wanner, Steen Ingemann, R. De Gelder, Jan H. van Maarseveen, Henk Hiemstra,

Axial and Atropisomeric Chirality Synthesis

Optically active tetrahydro-β-carbolines were synthesized via an (R)-BINOL-phosphoric acid-catalyzed asymmetric Pictet−Spengler reaction of N-benzyltryptamine with a series of aromatic and aliphatic aldehydes. The tetrahydro-β-carbolines were obtained in yields ranging from 77% to 97% and with ee values up to 87%. The triphenylsilyl-substituted BINOL-phosphoric acid proved to be the catalyst of choice for the reaction with aromatic aldehydes. For the aliphatic aldehydes, 3,5-bistrifluoromethylphenyl-substituted BINOL-phosphoric acid was identified as the best catalyst.