(2S)-N-{(1S,2S,4R)-2-Hydroxy-4-[5-(2-methylpropanoyl)imidazol-2-yl]-5-phenyl-1-benzylpentyl}-3-methyl-2-[(phenylmethoxy)carbonylamino]butanamide AIDS-028544 AIDS028544 SB 206343 SB-206343 Val-Phe-Phe-HOCH2CH2 isostere analog