(E)-(S)-4-[(S)-2-(3-{[1-(5-Methylisoxazol-3-yl)-methanoyl]-amino}-2-oxo-2H-pyridin-1-yl)-pent-4-ynoylamino]-5-((S)-2-oxopyrrolidin-3-yl)-pent-2-enoic acid cyclobutyl ester AIDS-177595 AIDS177595