N-Alkylthiocarbonyltryptophan (2a-i) and tryptamine (2j-m) derivatives can be converted into the corresponding 3, 4-dihydro-β-carbolines (3) under mild conditions by the use of alkylating or acylating agents. The NaBH4 reduction of 1, 3-disubstituted 3, 4-dihydro-β-carbolines (3a-i) gave cis- (5) or trans-1, 2, 3, 4-tetrahydro-β-carbolines (6) with satisfactory stereoselectivity. The synthesis of optically active 3a, b and 5a, b is also described.
