1,3,4-Thiadiazolo(3',2':1,2)pyrimido(5,4-b)indol-5(6H)-one, 2-ethyl- 116989-21-0 2-Ethyl-1,3,4-thiadiazolo(3',2':1,2)pyrimido(5,4-b)indol-5(6H)-one