. "2-{(2S,4S)-4-[1-(1-Carboxy-ethylcarbamoyl)-ethylamino]-2-methyl-pyrrolidin-1-yl}-9-(2,4-difluoro-phenyl)-3-fluoro-6-oxo-6H-pyrido[1,2-a]pyrimidine-7-carboxylic acid" . "12f-N-Ala-Ala" . . . . . . .