4,5,6,7-Tetrahydro-3-methyl-4-oxo-indole-2-carboxylic acid ethyl ester 5-22-06-00213 (Beilstein Handbook Reference) 7272-58-4 BRN 0477542 INDOLE-2-CARBOXYLIC ACID, 4,5,6,7-TETRAHYDRO-3-METHYL-4-OXO-, ETHYL ESTER