136471-32-4 2,9-Dimethyl-3a,4,9,9a-tetrahydrofuro(2,3-b)-quinoxaline-3-carboxylic acid Encyclan Furo(2,3-b)quinoxaline-3-carboxylic acid, 4,9-dihydro-2,9-dimethyl-, 1,7,7-trimethylbicyclo(2.2.1)hept-2-yl ester NSC 661582