Purin-6-one derivative

Represented by certain of formula (I), the expression, for example R2, R3, compounds R4 and R5 have the meanings given below are novel effective PDE2 inhibitors. R2 is Le, quinoxalinyl, cinnolinyl, quinolyl, isoquinolyl, naphthyridinyl, phthalazinyl, indolyl, isoindolyl, indazolyl, purinyl, pteridinyl, benzofuranyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl, imidazolyl, pyrrolyl, pyrazolyl, furanyl or thiophenyl, unsubstituted or identical or different halogen, respectively, hydroxyl, nitro, trifluoromethyl, R5 is halogen, hydroxyl, nitro, trifluoromethyl, Jill carbonyl amino, phenylsulfonyl amino, phenyl sulfonylamino substituted by R10 and / or R11 in the phenyl, benzyl sulfonylamino substituted with benzylsulfonyl amino or phenyl part by R12 and / or R13.