2,4-Dihydro-2,2'-dioxospiro(benz(c,d)indole-5(1H),3'-indoline)-3-carboxylic acid 73972-38-0 BRN 0899772 NSC 203299 Spiro(benz(c,d)indole-5(1H),3'-indoline)-3-carboxylic acid, 2,4-dihydro-2,2'-dioxo- Spiro(benz(cd)indole-5(1H),3'-(3H)indole)-3-carboxylic acid, 1',2,2',4-tetrahydro-2,2'-dioxo- (9CI)