The present invention relates to new compounds of formula (I) which are selective inhibitors of phosphodiesterase, their pharmaceutically acceptable salts or stereoisomers. The present invention also provides methods for preparing the compounds of formula (I) and new intermediates involved in the synthetic route of the compounds of formula (I). The compounds of formula (I) of the present invention are not only very effective for treatment of impotence diseases, such as male erectile dysfunction, but also have such features as long-lasting medical effectiveness and lower toxicity.
