PROBLEM TO BE SOLVED : To provide substituted benzaldehyde and a derivative thereof acts as an allosteric regulator of hemoglobin, a pharmaceutical composition containing the regulator, and an application method thereof in treatments of disorders mediated by haemoglobin and disorders in which increase of tissue oxidation is effective. SOLUTION : There are provided a compound represented by the following formula, a tautomer or a pharmaceutically acceptable salt thereof, and a pharmaceutical composition containing the same. In the formula, Q represents aryl, heteroaryl, heterocyclyl, Y and X represent O, methylene or the like, R6 and R7 represent groups forming oxo or aldehyde group together, R2 to R5 represent hydrogen, halo or the like. SELECTED DRAWING : None COPYRIGHT : (C)2019, JPO&INPIT