The novel heterocyclic derivative of the present invention is a novel
heterocyclic derivative having the formula (I')
##STR1##
wherein R.sup.1 is a hydrogen atom or C.sub.1-6 alkyl, R.sup.2 is
--CO--C(R.sup.4).dbd.C(R.sup.4)--R.sup.5 wherein R.sup.4 is a hydrogen
atom or C.sub.1-4 alkyl, and R.sup.5 is C.sub.4-8 alkyl, C.sub.2-8
alkenyl, aryl or aromatic heterocycle, --CO--C.ident.C--R.sup.6 wherein
R.sup.6 is C.sub.1-8 alkyl and the like, R.sup.3 is a hydrogen atom or
C.sub.1-4 alkyl, X is an oxygen atom or a sulfur atom, R.sup.20 is
optionally substituted phenyl, and n is an integer of 1 to 4, or a
pharmaceutically acceptable salt thereof. The compound (I') of the present
invention is useful as a hypoglycemic agent, a hypolipidemic agent, an
insulin resistance improver, a therapeutic agent of diabetes, a
therapeutic agent of diabetic complications, a glucose tolerance improver,
an anti-arteriosclerosis agent, an anti-obesity agent, an antiinflammatory
agent, an agent for the prophylaxis or treatment of PPAR-mediated diseases
and an agent for the prophylaxis or treatment of syndrome X.
