Disclosed is a compound useful as an active ingredient for medicines having PDE4B inhibiting activity, in particular, therapeutic or preventive medicinal compositions for schizophrenia, Alzheimers disease, dementia, depression and the like. Specifically, the present inventors examined compounds having PDE4B inhibiting activity and found that a tricyclic or tetracyclic imidazo[1,2-a]pyridine derivative or salts thereof had superior PDE4B inhibiting activity. This imidazo[1,2-a]pyridine derivative can be used in therapeutic and preventative agents for schizophrenia, Alzheimers disease, dementia, depression, and the like.本發明提供一種可使用作為具有PDE4B抑制活性之醫藥,尤其是精神分裂症、阿茲海默症、失智症、憂鬱症等之治療或預防用醫藥組成物之有效成分之化合物。本發明人等針對具有PDE4B抑制活性之化合物進行檢討,確認3環性或4環性之咪唑[1,2-a]吡啶衍生物或其鹽具有優異之PDE4B抑制活性,因而完成本發明。本發明之咪唑[1,2-a]吡啶衍生物能夠使用作為精神分裂症、阿茲海默症、失智症、憂鬱症等之治療或預防劑。
