Asymmetric Steering of the Pictet-Spengler Reaction by Means of Amino Acid Esters as Chiral Auxiliary Groups

Article abstract of DOI:10.1016/S0040-4020(01)89301-7

N-β-(3-Indolyl)ethyl amino acid esters and differently substituted aromatic aldehydes in the presence of acetic acid form iminium intermediates which at 6 degC to 40 degC undergo Pictet-Spengler cyclizations to give tetrahydro-β-carbolines with diastereomer ratios up to 98.5:1.5.The chiral auxiliary group is removed from the heterocycles by employing a retro Strecker reaction as the key transformation.