PHTHALAZONE DERIVATIVE, ITS PREPARATION AND USE

NEW MATERIAL:The phthalazone derivative of formula I (R is H or lower alkyl; A is group of formula II or formula III; n is 0-14). EXAMPLE:7-Ethoxycarbonyl-6,8-dimethyl-1( 2H )-phthalazinon-4-ylmethyl hydrogen succinate. USE:Useful as a biotransformation precursor of phthalazinol which is useful as a preventive and remedy for hypertensive, arteriosclerotic and thrombotic diseases. The compound is converted to phthalazinol in the body to exhibit the pharmacological activity, and is useful as a remedy for angiopathy. PROCESS:Phthalazinol of formula IV is esterified with a carboxylic acid or its functional derivative, and the 4-hydroxymethyl group is converted to CH2-A-OR group to obtain the compound of formula I . The carboxylic acid or its functional derivative is, e.g. oxalic acid, adipic acid monoethyl ester, etc.