Enantioselective synthesis of 1-substituted tetrahydro-β-carboline derivatives via the asymmetric transfer hydrogenation

Several 1-substituted-3,4-dihydro-β-carboline derivatives were subjected to asymmetric transfer hydrogenation catalysed by chiral ruthenium complexes to give both enantiomers of 1,2,3,4-tetrahydro-β-carbolines of high optical purity and in good yields. The absolute stereochemistry of 4c was established on the basis of X-ray analysis of its Mosher's amide.