AIDS-028542 AIDS028542 N-[(1S)-1-(N-{Imino[(phenylmethoxy)carbonylamino]methyl}carbamoyl)-2-methylpropyl](4S,5S,2R)-5-[(tert-butoxy)carbonylamino]-4-hydroxy-6-phenyl-2-benzylhexanamide SB 205569 SB-205569 Val-Phe-Phe-HOCH2CH2 isostere analog