4-{3-[1-(2-Cyclopropylethyl)-6-fluoro-4-hydroxy-2-oxo-1,2-dihydroquinolin-3-yl]-1,1-dioxo-1,4-dihydrobenzo[1,2,4]thiadiazin-7-yl}-2,4-dioxobutyric acid, methyl ester AIDS-221852 AIDS221852