PROBLEM TO BE SOLVED: To provide a novel furanone derivatives having an inhibition effect on a serine threonine protein kinase Cdc 7.SOLUTION: Furanone derivatives of formula (I) and their pharmaceutically acceptable salts are provided. In the formula, A is -COOR1 or H； R1 is H or a substituted/unsubstituted hydrocarbon group or a heterocycle； R2 and R3 are identical or different and H, a substituted/unsubstituted hydrocarbon group, a phenyl group, a heterocycle, a condensed heterocyclic ring or an amino group； R2 and R3, together with a nitrogen atom to which they are bonded, may form a heterocycle or a condensed heterocyclic ring； and R4 is H or a halogen atom.【課題】セリンスレオニンプロテインキナーゼの一種Ｃｄｃ７阻害作用を有する新規なフラノン誘導体の提供。【解決手段】式（Ｉ）で表されるフラノン誘導体又はその薬学的に許容される塩。（Ａは－ＣＯＯＲ１若しくはＨ；Ｒ１はＨ、置換／未置換の炭化水素基、複素環；Ｒ２及びＲ３は同一又は異なって、Ｈ、置換／未置換の炭化水素基、フェニル基、複素環、複素環式縮合環又はアミノ基或いは、Ｒ２及びＲ３は、これらが結合している窒素原子と共に、複素環、縮合複素環を形成してもよい；Ｒ４はＨ又はハロゲン原子）【選択図】なし
