Heteroarylcarboxylic acid ester derivative

1. A method for treating hyperglycemia or diabetes, comprising administering an effective amount of a compound represented by formula (I):

wherein:

R 1 and R 2 are the same or different and each is independently a C 1-4 alkyl group or a C 2-4 alkenyl group, or R 1 and R 2 together with the carbon atom to which they are bonded form a C 3-8 cycloalkane ring;

X is —OR 3 , —NR 4 R 5 or a group represented by formula (II):

wherein:

R 3 is a hydrogen atom or a C 1-4 alkyl group;

R 4 , R 5 and R 6 are the same or different and each is independently a hydrogen atom, a C 1-8 alkyl group, a carboxyl C 1-8 alkyl group or a C 3-8 alkenyl group, or R 4 and R 5 together with the nitrogen atom to which they are bonded form a C 3-9 heterocycle, wherein said C 1-8 alkyl group, said C 3-8 alkenyl group and said C 3-9 heterocycle may be substituted with one or more substituents;

Ra and Rb are the same or different and each is independently a hydrogen atom, a C 1-8 alkyl group, a carboxyl C 1-8 alkyl group, a carboxyl group, an aryl group, a C 3-6 heterocyclic group containing 1 to 4 heteroatoms selected from the group consisting of O, N and S, or a C 3-8 cycloalkyl group, or Ra and Rb together with the atom(s) to which they are bonded form a C 3-8 cycloalkane ring or a C 3-9 heterocycle containing 1-4 heteroatoms selected from the group consisting of O, N and S, wherein said C 1-8 alkyl group, said aryl group, said C 3-8 cycloalkyl group, said C 3-8 cycloalkane ring and said C 3-9 heterocycle may be substituted with one or more substituents;

Ring A is an arene, a C 3-6 heterocycle containing 1-4 heteroatoms selected from the group consisting of O, N and S, or a C 3-8 cycloalkane ring;

Ya is a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a carbonyl group, a carboxyl C 1-3 alkyl group or a sulfo group;

Yb is a hydrogen atom, a halogen atom, a carboxyl group, a hydroxyl group, a carbonyl group, a carboxyl C 1-3 alkyl group, a nitro group, a cyano group or a C 1-3 alkoxyl group;

p is 0, 1, 2, 3 or 4;

q is 0 or 1; and

R 7 is a hydrogen atom, a halogen atom or a nitro group;

with the proviso that when R 1 and R 2 are both methyl groups, then neither of R 4 nor R 5 is an ethyl group substituted with two carboxyl groups, and when R 1 and R 2 are both methyl groups, then the group represented by formula (II) is not a group represented by formula:

or a pharmaceutically acceptable salt thereof,

to a subject in need thereof.

2. The method according to claim 1 , wherein X is —NR 4 R 5 or a group represented by formula (II), wherein R 4 , R 5 and R 6 are each independently a hydrogen atom or a C 1-8 alkyl group.

3. The method according to claim 1 , wherein X is —NR 4 R 5 , wherein R 4 and R 5 together with the nitrogen atom to which they are bonded form a C 3-9 heterocycle substituted by a hydrogen atom, a halogen atom, a carboxyl group, a carboxyl C 1-3 alkyl group or a hydroxyl group.

4. The method according to claim 1 , wherein X is a group represented by formula (II), wherein p=1 or 2, and q=0.

5. The method according to claim 1 , wherein X is a group represented by formula (II), wherein p=0 and q=1.

6. The method according to claim 1 , wherein X is a group represented by formula (II), wherein p=1, q=1, and Ra and Rb are the same or different and each is independently a hydrogen atom or a C 1-8 alkyl group, or Ra and Rb together with the atom(s) to which they are bonded form a C 3-8 cycloalkane ring, wherein said C 1-8 alkyl group and said C 3-8 cycloalkane ring may substituted with a group selected from the group consisting of a hydrogen atom, a carboxyl group, a carbamoyl group, a hydroxyl group, a phenyl group and a C 3-8 cycloalkyl group.

7. The method according to claim 1 , wherein R 1 and R 2 are the same or different and each is independently a methyl group, an ethyl group or a propyl group, or R 1 and R 2 together with the carbon atom to which they are bonded form a cyclobutane ring or a cyclopentane ring.

8. The method according to claim 1 , wherein X is a group represented by formula (II), wherein q=1, and Ring A is a benzene ring, a pyridine ring, or a C 1-6 heterocycle containing 1-4 oxygen atoms.

9. The method according to claim 1 , wherein X is a group represented by formula (II), wherein q=1, Ya is a halogen atom, a carboxyl group, a carboxyl C 1-3 alkyl group, a hydroxyl group, a sulfo group or a carbonyl group, and Yb is a hydrogen atom, a halogen atom, a carboxyl group or a hydroxyl group.

10. The method according to claim 1 , wherein X is —NR 4 R 5 , wherein when R 4 or R 5 has substituent(s), said substituent is selected from the group consisting of a halogen atom, a carboxyl group, a hydroxyl group, a carboxyl C 1-3 alkyl group, a C 3-8 alkenyl group, a carbamoyl group, a phenyl group, an amino group, a sulfo group, a cyano group, a C 3-8 cycloalkyl group, and a C 1-8 heterocyclic group containing 1 to 4 heteroatoms selected from the group consisting of O, N and S.

11. The method according to claim 1 , wherein X is a group represented by formula (II), wherein, when Ra or Rb has substituent(s), said substituent is selected from the group consisting of a carboxyl group, a hydroxyl group, a phenyl group, an amino group, a methylthio group, a thiol group, a carbamoyl group, a guanidino group, a C 3-8 cycloalkyl group, and a C 1-8 heterocyclic group containing 1-4 heteroatoms selected from the group consisting of O, N and S.

12. The method according to claim 1 , wherein, said compound represented by formula (I) is a compound represented by any of the following formulae:

13. The method according to claim 1 , wherein said compound represented by formula (I) is a compound represented by any of the following formulae: