AIDS-006864 AIDS006864 Difluorostatone mimetic MDL 104,168 MDL 73,669 analog [9(S),12(S)]-.alpha.,.alpha.-Difluoro-9-(1-methylethyl)-.beta.,4,7,10-tetraoxo-N-(phenylmethyl)-2-oxa-5,8,11-tetrabicyclo-[12.2.2]octadeca-14,16,17-triene-12-propanamide