160893-91-4 5H-1,3,4-Thiadiazolo(2,3-b)quinazoline-5-thione, 6,7,8,9-tetrahydro-2-methyl- 6,7,8,9-Tetrahydro-2-methyl-5H-1,3,4-thiadiazolo(2,3-b)quinazoline-5-thione