(EN) A process for preparing a compound represented by formula (Y1) or (Y2) [wherein R x is an optionally substituted carbocyclyl lower alkyl, or the like] or a salt thereof, using a novel process for preparing a pyridone derivative represented by formula (X4) [wherein R 1d is hydrogen, halogen, or the like; R 2d is hydrogen, a lower alkyl optionally substituted with substituent E, or the like; R 4d is a lower alkyl optionally substituted with substituent E, or the like; and R 6d is a lower alkyl group optionally substituted with substituent group E, or the like].
(ZH) 式(Y1)或式(Y2)(式中,RX为可被取代的碳环低级烷基等)所示的化合物或其盐的制造方法,其使用了式(X4)(式中,R1d为氢、卤素等,R2d为氢、可被取代基组E取代的低级烷基等,R4d为可被取代基组E取代的低级烷基等,以及R6d为可被取代基组E取代的低级烷基等)所示的吡啶酮衍生物的新的制造方法。