(2R)-N-{3-[(2S)-3-Methyl-2-(2-quinolylcarbonylamino)butanoylamino](3S,2R)-2-hydroxy-4-phenylbutyl}-2-(tert-butyl)-N'-(ethylpropyl)butane-1,4-diamide (OHEt)amide isostere AIDS-050404 AIDS050404