Dihydroindolizinone derivative

A compound represented by formula (I):

• wherein each substituent is defined as follows:
• R1 represents a hydrogen atom, a halogen atom, or a C1-C6 alkyl group;
• R2 represents a hydrogen atom or a C1-C6 alkyl group;
• R3 represents an aryl group optionally substituted with one to four substituents independently selected from a substituent group α, a C5-C10 cycloalkenyl group optionally substituted with one to four substituents independently selected from a substituent group α, or a heterocyclyl group optionally substituted with one to four substituents independently selected from a substituent group α;
• the substituents of substituent group α are selected from the group consisting of a halogen atom, a cyano group, a carboxy group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a halogeno-C1-C6 alkyl group, a halogeno-C1-C6 alkoxy group, a hydroxy C1-C6 alkyl group, a C1-C6 alkoxy C1-C6 alkoxy group, a (C1-C6 alkyl)carbonyl group, a (C1-C6 alkoxy)carbonyl group, a (C1-C6 alkoxy)carbonyloxy group, a phenyl C1-C6 alkoxy group, a non-aromatic heterocyclyl group, a carbamoyl group optionally substituted with one or two C1-C6 alkyl groups, a C1-C6 alkoxy group substituted by a carbamoyl group optionally substituted with one or two C1-C6 alkyl groups, a sulfamoyl group substituted with one or two C1-C6 alkyl groups, a phenoxy group optionally substituted with one to four substituents independently selected from a substituent group β, a phenyl group optionally substituted with one to four substituents independently selected from the substituent group β, and a benzoyl group optionally substituted with one to four substituents independently selected from the substituent group β;
• the substituents of substituent group β are selected from the group consisting of a halogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, a halogeno-C1-C6 alkyl group, a halogeno-C1-C6 alkoxy group, and a (C1-C6 alkoxy)carbonyl group;
• n represents 0 or 1;
• and
• A represents a group represented by any one of formulas (i) to (iv) below:
• wherein each substituent is defined as follows:
• ⋅ and * each represent a bond, where ⋅ is bonded to the nitrogen atom of the amido group of formula (I), and * is bonded to R3;
• R4 represents a hydrogen atom, a C1-C6 alkyl group, a halogeno-C1-C6 alkyl group, or a (C1-C6 alkoxy)carbonyl group;
• R5 represents a hydrogen atom, a halogen atom, or a C1-C6 alkyl group;
• and
• Y represents N or CH;
• or a stereoisomer or a salt thereof.