2,2',3,3',5,5',6,6'-Octafluoro-4'-mercapto[1,1'-biphenyl]-4-yl hydrosulfide 2,2',3,3',5,5',6,6'-Octafluoro[1,1'-biphenyl]-4,4'-dithiol 21386-21-0 AIDS-126044 AIDS126044 NSC97023