Abstract: A 2,6,7,8-substituted quinazoline represented by the following formula ##STR1## wherein R.sub.1 and R.sub.3 each represent a lower alkyl group, R.sub.2 represents a lower alkoxy-carbonyl group, and A represents a lower alkyl group, or a phenyl or benzyl group which is unsubstituted or substituted by a substituent selected from the class consisting of halogen atoms, a trifluoromethyl group and lower alkyl groups, or its acid addition salt. The said compound can be prepared by reacting a compound represented by the following formula ##STR2## wherein R.sub.1, R.sub.2, R.sub.3 and A are as defined, with ammonia. A pharmaceutical composition comprising the said compound as an active ingredient is useful for the treatment of disorders of the circulatory system.

Abstract: Novel 1-phthalazone derivatives of the following formula ##STR1## wherein R.sub.1, R.sub.2 and R.sub.3 are as defined in claim 1, and pharmaceutically acceptable acid addition salts thereof; a process for production thereof; a pharmaceutical composition containing said compound; and a method for treating a thrombotic disease using said compound.

Abstract: Novel 3-aromatic moiety substituted-4(3H)-quinazolinone derivatives useful as a vasodilators, hypotensive and antiatherosclerotic agents having the formula of ##STR1## wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4 and Q are as defined in the accompanying specification or its acid addition salt; and a process for producing the same.