The cinchona alkaloid squaramide catalyzed asymmetric Pictet-Spengler reaction and related theoretical studies

The asymmetric Pictet-Spengler reaction between tryptamine derivatives and aldehydes has been developed with a cinchona alkaloid squaramide as the catalyst, affording the corresponding tetrahedron-beta-carbolines in good to excellent yields and ee values. A rational mechanistic pathway has also been proposed based on DFT calculations.