Enantiopure tetrahydroisoquinolines via N-sulfinyl Pictet–Spengler reactions

Asymmetric Pictet–Spengler reactions with (R)-N-p-tolylsulfinyl-3,4-dimethoxyphenylethyl amine proceeded with high diastereoselectivity. Starting from the commercially available (R)- and (S)-Andersen reagents a highly efficient route to (+)- and (−)-salsolidine and related tetrahydroisoquinolines was developed.