1-(beta-Carboxyethyl)-3,3-dimethyl-6'-nitrospiro(indoline-2,2'-2H-benzopyran) 55779-26-5 Benzospiropyran Spiro(2H-1-benzopyran-2,2'-(2H)indole)-1'(3'H)-propanoic acid, 3',3'-dimethyl-6-nitro-