Elvitegravir 2,3-difluro Impurity

: (S) Ethyl 6-(2,3-difluorobenzyl)-1-(1-hydroxy-3-methylbutan-2-yl)-7-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylate;Ethyl (S)-6-(2,3-difluorobenzyl)-1-(1-hydroxy-3-methylbutan-2-yl)-7-methoxy-4-oxo-1,4-dihydroquinoline-3-carboxylate ;