Heterocyclic compounds

1. A heterocyclic compound represented by formula (I′)

wherein R 1 is an alkyl group optionally having substituent(s), a cycloalkyl group optionally having substituent(s), a cycloalkylalkyl group optionally having substituent(s), an aralkyl group optionally having substituent(s), an aryl group optionally having substituent(s), a heteroaryl group optionally having substituent(s), a heteroarylalkyl group optionally having substituent(s), a cycloalkyl group containing hetero atom(s) in its ring optionally having substituent(s) or a cycloalkylalkyl group containing hetero atom(s) in its ring,

R 2 and R 3 are the same or different and each is a hydrogen atom, a hydroxyl group, an alkyl group optionally having substituent(s) or an aralkyl group optionally having substituent(s), or may be linked to form a cycloalkyl group, a cycloalkyl group containing hetero atom(s) in its ring,

wherein R 5 and R 6 are the same or different and each is a hydrogen atom, an alkoxy group, an alkoxycarbonyl group, an alkyl group optionally having substituent(s), an aralkyl group optionally having substituent(s), an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s), or may be linked to form a cycloalkyl group or a cycloalkyl group containing hetero atom(s) in its ring,

wherein R 7 is an aryl group optionally having substituent(s), ═N—R 8 wherein R 8 is a hydroxyl group, an alkoxy group, an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s), ═N—NH—R 9 wherein R 9 is an aryl group optionally having substituent(s), a heteroaryl group optionally having substituent(s), an acyl group or a carbamoyl group, or ═O,

R 4 is a hydrogen atom, an alkyl group optionally having substituent(s) or an aralkyl group optionally having substituent(s),

X is a hydrogen atom, a halogen atom, a hydroxyl group, an alkyl group optionally having substituent(s), an aralkyl group optionally having substituent(s), an alkoxy group optionally having substituent(s), an aryl group optionally having substituent(s), a heteroaryl group optionally having substituent(s), an amino group optionally having substituent(s) selected from the group consisting of alkyl group, aralkyl group optionally having substituent(s), acyl group, cycloalkyl group, cycloalkylalkyl group, alkoxycarbonyl group, and aralkyloxycarbonyl group, 1-piperidyl group, 1-piperazyl group, morpholin-4-yl group, an alkylthio group optionally having substituent(s), an aralkylthio group optionally having substituent(s), an arylthio group optionally having substituent(s), a heteroarylthio group optionally having substituent(s), an alkylsulfonyl group optionally having substituent(s), an aralkylsulfonyl group optionally having substituent(s), an arylsulfonyl group optionally having substituent(s), a heteroarylsulfonyl group optionally having substituent(s), or an alkoxycarbonylthio group, and

Y is an oxygen atom or a sulfur atom,

provided that, when Y is an oxygen atom, R 1 is a phenyl group or a 2-carboxyethyl group or a methyl group, and X is an amino group, then all of R 2 , R 3 and R 4 are not hydrogen atoms at the same time;

when Y is an oxygen atom, R 1 is a phenyl group, X is an amino group and R 4 is a hydrogen atom, then both R 2 and R 3 are not methyl groups at the same time;

when Y is an oxygen atom, R 1 is a phenyl group, X is an amino group, R 4 is a hydrogen atom and one of R 5 and R 6 is a hydrogen atom, then the other of R 5 and R 6 is not a phenyl group or a 3-pyridyl group;

when Y is an oxygen atom, R 1 is a phenyl group, X is a phenyl group and R 4 is a hydrogen atom, then both R 2 and R 3 are not hydrogen atoms at the same time or are not linked to form ═N—NH—R 9 ′ (wherein R 9 ′ is a phenyl group);

when Y is an oxygen atom, R 1 is a phenyl group, X is a phenyl group, R 4 is a hydrogen atom and one of R 5 and R 6 is a hydrogen atom, then the other of R 5 and R 6 is not a phenyl group or a 4-chlorophenyl group; and

when Y is an oxygen atom, R 1 is a 2-carboxyethyl group, X is an amino group, R 4 is a hydrogen atom and one of R 5 and R 6 is a hydrogen atom, then the other of R 5 and R 6 is not a phenyl group,

or a pharmaceutically acceptable salt thereof.

2. The heterocyclic compound of claim 1 , wherein

R 1 is an alkyl group optionally having substituent(s), a cycloalkyl group optionally having substituent(s), a cycloalkylalkyl group optionally having substituent(s), an aralkyl group optionally having substituent(s), an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s)

or a pharmaceutically acceptable salt thereof.

3. The heterocyclic compound of claim 1 , wherein

R 4 is a hydrogen atom,

X is a halogen atom, an amino group optionally having substituent(s) selected from the group consisting of alkyl group, aralkyl group optionally having substituent(s), acyl group, cycloalkyl group, cycloalkylalkyl group, alkoxycarbonyl group, and aralkyloxycarbonyl group, 1-piperidyl group, 1-piperazyl group, morpholin-4-yl group, an alkylthio group optionally having substituent(s), an aralkylthio group optionally having substituent(s), an arylthio group optionally having substituent(s) or a heteroarylthio group optionally having substituent(s), and

Y is an oxygen atom,

or a pharmaceutically acceptable salt thereof.

4. The heterocyclic compound of claim 3 , wherein

R 1 is an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s),

R 2 and R 3 may, in combination, form

wherein R 5 and R 6 are the same or different and each is a hydrogen atom, an alkoxy group, an alkoxycarbonyl group, an alkyl group optionally having substituent(s), a cycloalkyl group optionally having substituent(s), an aralkyl group optionally having substituent(s), an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s), or may be linked to form a cycloalkyl group or a cycloalkyl group containing hetero atom(s) in its ring, and

X is a halogen atom or an amino group optionally having substituent(s) selected from the group consisting of alkyl group, aralkyl group optionally having substituent(s), acyl group, cycloalkyl group, cycloalkylalkyl group, alkoxycarbonyl group, and aralkyloxycarbonyl group, 1-piperidyl group, 1-piperazyl group, morpholin-4-yl group,

or a pharmaceutically acceptable salt thereof.

5. The heterocyclic compound of claim 4 , wherein R 1 is a phenyl group optionally having substituent(s), and X is an amino group,

or a pharmaceutically acceptable salt thereof.

6. The heterocyclic compound of claim 1 , wherein

R 2 and R 3 are hydrogen atoms,

R 4 is a hydrogen atom,

X is a halogen atom or an amino group optionally having substituent(s) selected from the group consisting of alkyl group, aralkyl group optionally having substituent(s), acyl group, cycloalkyl group, cycloalkylalkyl group, alkoxycarbonyl group, and aralkyloxycarbonyl group, 1-piperidyl group, 1-piperazyl group, morpholin-4-yl group, and

Y is an oxygen atom,

or a pharmaceutically acceptable salt thereof.

7. The heterocyclic compound of claim 6 , wherein X is an amino group,

or a pharmaceutically acceptable salt thereof.

8. The heterocyclic compound of claim 1 , wherein

R 1 is an alkyl group optionally having substituent(s), a cycloalkyl group optionally having substituent(s), a cycloalkylalkyl group, an aralkyl group optionally having substituent(s), an aryl group optionally having substituent(s), a heteroaryl group, a heteroarylalkyl group or a cycloalkyl group containing hetero atom(s) in its ring optionally having substituent(s),

R 2 and R 3 are the same or different and each is a hydrogen atom, a hydroxyl group, an alkyl group optionally having substituent(s) or an aralkyl group optionally having substituent(s), or may, in combination, form a cycloalkyl group,

wherein R 5 a and R 6 a are the same or different and each is a hydrogen atom, an alkoxycarbonyl group, an alkyl group optionally having substituent(s), a cycloalkyl group, an aryl group optionally having substituent(s) or a heteroaryl group optionally having substituent(s), or may be linked to form a cycloalkyl group or a cycloalkyl group containing hetero atom(s) in its ring,

wherein R 7 is an aryl group optionally having substituent(s), ═N—R 8 a wherein R 8 a is a hydroxyl group, an alkoxy group or an aryl group optionally having substituent(s)), ═N—NH—R 9 a wherein R 9 a is an aryl group optionally having substituent(s), an acyl group or a carbamoyl group, or ═O,

R 4 is a hydrogen atom, an alkyl group or an aralkyl group, and

X is a hydrogen atom, a halogen atom, a hydroxyl group, an aryl group optionally having substituent(s), a heteroaryl group optionally having substituent(s), an amino group optionally having substituent(s) selected from the group consisting of alkyl group, aralkyl group optionally having substituent(s), acyl group, cycloalkyl group, cycloalkylalkyl group, alkoxycarbonyl group, and aralkyloxycarbonyl group, 1-piperidyl group, 1-piperazyl group, morpholin-4-yl group, an alkylthio group optionally having substituent(s), aralkylthio group, an arylthio group optionally having substituent(s), an alkylsulfonyl group, an arylsulfonyl group optionally having substituent(s), or an alkoxycarbonylthio group,

or a pharmaceutically acceptable salt thereof.

9. A heterocyclic compound selected from the group consisting of

and pharmaceutically acceptable salts thereof.

10. A pharmaceutical composition, which comprises a heterocyclic compound according to claim 1 or a pharmaceutically acceptable salt thereof, and

a pharmaceutically acceptable carrier.

11. The pharmaceutical composition of claim 10 , wherein said pharmaceutically acceptable carrier is at least one member selected from the group consisting of an excipient, a diluent, an extender, a disintegrant, a stabilizer, a preservative, a buffer, an emulsifier, a flavoring agent, a coloring agent, a sweetening agent, a thickener, a corrigent, a solubilizer, and mixtures thereof.

12. The pharmaceutical composition of claim 10 , which is in a form selected from the group consisting of a tablet, a pill, a powder, a granule, a suppository, a liquid, a capsule, a troche, and an aerosol.

13. A pharmaceutical composition, which comprises a heterocyclic compound according to claim 9 or a pharmaceutically acceptable salt thereof, and

a pharmaceutically acceptable carrier.

14. The pharmaceutical composition of claim 13 , wherein said pharmaceutically acceptable carrier is at least one member selected from the group consisting of an excipient, a diluent, an extender, a disintegrant, a stabilizer, a preservative, a buffer, an emulsifier, a flavoring agent, a coloring agent, a sweetening agent, a thickener, a corrigent, a solubilizer, and mixtures thereof.

15. The pharmaceutical composition of claim 13 , which is in a form selected from the group consisting of a tablet, a pill, a powder, a granule, a suppository, a liquid, a capsule, a troche, and an aerosol.