CuBr2-Catalyzed Mild Oxidation of34-Dihydro-β-Carbolines and Application in Total Synthesisof 6-Hydroxymetatacarboline D

摘要

A green chemical method for the conversion of 3,4-dihydro-β-carbolines to β-carbolines has been developed using air as the oxidant. With 15 mol % CuBr2 as the catalyst, 3,4-dihydro-β-carbolines could be efficiently oxidized to β-carbolines in dimethyl sulfoxide at room temperature in the presence of 1,8-diazabicyclo[5,4,0]undec-7-ene (or Et3N). By applying this method, the first total synthesis of 6-hydroxymetatacarboline D was performed through 12 steps in 22% overall yield starting from l-5-hydroxy-tryptophan.