Patent ID: 8552037

Claim:
A compound represented by the formula: wherein R 1 is a hydrocarbon group optionally having substituent(s), amino optionally having substituent(s), hydroxy optionally having a substituent or a heterocyclic group optionally having substituent(s); R 2 is a hydrogen atom, a halogen atom, a hydrocarbon group optionally having substituent(s) or a heterocyclic group optionally having substituent(s); R 3 is a hydrogen atom, a hydrocarbon group optionally having substituent(s), amino optionally having substituent(s), hydroxy optionally having a substituent, mercapto optionally having a substituent or a heterocyclic group optionally having substituent(s); R 4a and R 4b are the same or different and each is a hydrogen atom, a halogen atom, a hydrocarbon group optionally having substituent(s), amino optionally having substituent(s), hydroxy optionally having a substituent or mercapto optionally having a substituent; R 5 is a hydrogen atom, a halogen atom, a hydrocarbon group optionally having substituent(s), amino optionally having substituent(s), hydroxy optionally having a substituent or mercapto optionally having a substituent; R 6 is a hydrogen atom or a hydrocarbon group optionally having substituent(s); X is an oxygen atom or a sulfur atom; and shows a single bond or a double bond, or a pharmaceutically acceptable salt or prodrug thereof.