The present invention relates to oxygen-containing heterocyclic compounds represented by the following formula (I):
1
wherein m represents an integer of 0 to 4; R
1
, R
2
, R
3
and R
4
independently represent a hydrogen atom, substituted or unsubstituted lower alkyl, etc.; R
5
represents substituted or unsubstituted lower alkoxy etc.; R
6
represents a hydrogen atom etc.; and Y represents the following formula (II):
2
wherein R
9
represents cyano etc., R
10
represents a hydrogen atom etc., R
1
represents carboxy etc., and R
2
represents a hydrogen atom etc.; and the like; or pharmaceutically acceptable salts thereof.