AIDS-051257 AIDS051257 Ethyl 4-(4-{(3R)-2-[(2S)-2-(acetylamino)-3-carbamoylpropanoylamino]-4-[2-(N-{(2S)-1-[N-(1-carbamoyl-2-methylpropyl)carbamoyl]-2-methylbutyl}carbamoyl)pyrrolidinyl]-3-hydroxybutyl}phenoxy)butanoate