Abstract: A production process with good efficiency, and applicable to production of a synthetic intermediate of a new quinolone anti-fungus agent CP-99219, is provided.A production process of an intermediate of a new quinolone compound expressed by the formula (IV) ##STR1## wherein R.sup.3 represents a benzyl group, a diphenylmethyl group, etc. and R.sup.4 represents a linear or branched alkyl group of 1 to 8C, a cycloalkyl group, etc.which process employs as a starting substance, a cyclopropanetricarboxylic acid triester expressed by the formula (I) ##STR2## wherein R.sup.1 and R.sup.2 represent a linear or branched alkyl group, a cycloalkyl group, an aryl group or an aralkyl group,and passes through seven steps.