2-(5,6-Dihydro[1,3]dithiolo[4,5-b][1,4]dithiin-2-ylidene)-4a,6,7,8a-tetrahydro[1,3]dithiolo[4',5':5,6][1,4]dithiino[2,3-b][1,4]dioxine AIDS-150985 AIDS150985 NSC689739