| abstract |
The present invention provides a compound which has the effect of PDE inhibition, and which is useful as a medicament for preventing or treating schizophrenia or so on. n A compound of formula (I 0 ): n n n n n n n n n n n n wherein n R 1 represents n a substituent, n R 2 represents n a hydrogen atom, or a substituent, n R 3 represents n a hydrogen atom, or a substituent, n Ring A represents n an aromatic ring which can be substituted, and n Ring B represents n a 5-membered heteroaromatic ring which can be substituted, n or a salt thereof. |