1,2,3,4-Tetrahydro-beta-carboline-3-carboxylic acid 1H-Pyrido(3,4-b)indole-3-carboxylic acid, 2,3,4,9-tetrahydro- 6052-68-2 CCRIS 6486 NSC 96912 Tetrahydro-beta-carboline-3-carboxylic acid