Patent ID: 6872732

Claim:
A novel heterocyclic derivative of the formula (I′) wherein R 1 is a hydrogen atom or C 1-6 alkyl, R 2 is —CO—C(R 4 )═C(R 4 )—R 5 wherein R 4 is a hydrogen atom or C 1-4 alkyl, and R 5 is C 4-8 alkyl, C 2-8 alkenyl, aryl or aromatic heterocycle, —CO—C≡C—R 6 wherein R 6 is C 1-8 alkyl, —CO—CO—R 7 wherein R 7 is C 1-8 alkyl or C 1-8 alkoxy, —N(R 8 )—CO—R 9 wherein R 8 is a hydrogen atom or C 1-4 alkyl, and R 9 is C 1-8 alkyl, C 1-8 alkoxy, aryl or aryl C 1-3 alkoxy, or aryl, R 3 is a hydrogen atom or C 1-4 alkyl, X is an oxygen atom or a sulfur atom, R 20 is optionally substituted phenyl, and n is an integer of 1 to 4, or a pharmaceutically acceptable salt thereof.