CuBr2-Catalyzed Mild Oxidation of 3,4-Dihydro-ß-Carbolines and Application in Total Synthesis of 6-Hydroxymetatacarboline D.

A green chemical method for the conversion of 3,4-dihydro-ß-carbolines to ß-carbolines has been developed using air as the oxidant. With 15 mol % CuBr2 as the catalyst, 3,4-dihydro-ß-carbolines could be efficiently oxidized to ß-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.

Cu-catalyzed mild and efficient oxidation of THßCs using air: application in practical total syntheses of perlolyrine and flazin.

A mild, efficient and environmentally benign method for synthesis of aromatic ß-carbolines via Cu(ii)-catalyzed oxidation of 1,2,3,4-tetrahydro-ß-carbolines (THßCs) was developed, in which air (O2) was used as the clean oxidant. This method has advantages such as environmentally friendliness, mildness, very good tolerance of functional groups, high yielding and easy experiment operation. In addition, this new methodology was successfully applied in the efficient and practical total syntheses of ß-carboline alkaloids perlolyrine and flazin.

Novel total syntheses of oxoaporphine alkaloids enabled by mild Cu-catalyzed tandem oxidation/aromatization of 1-Bn-DHIQs.

Novel total syntheses of oxoaporphine alkaloids such as liriodenine, dicentrinone, cassameridine, lysicamine, oxoglaucine and O-methylmoschatoline were developed. The key step of these total syntheses is Cu-catalyzed conversion of 1-benzyl-3,4-dihydro-isoquinolines (1-Bn-DHIQs) to 1-benzoyl-isoquinolines (1-Bz-IQs) via tandem oxidation/aromatization. This novel Cu-catalyzed conversion has been studied in detail, and was successfully used for constructing the 1-Bz-IQ core.