2-{(2S,4S)-4-[(S)-2-((S)-2-Amino-propanoylamino)-propanoylamino]-2-methyl-pyrrolidin-1-yl}-9-(2,4-difluoro-phenyl)-3-fluoro-6-oxo-6H-pyrido[1,2-a]pyrimidine-7-carboxylic acid AIDS-094508 AIDS094508