PROCESS FOR PRODUCING SOLIFENACIN OR ITS SALT

A novel process for producing solifenacin or its salt that is useful as a medicine, especially a therapeutic agent and/or preventive agent for urinary diseases, such as frequent urination and involuntary urination. In particula r, there are provided (1) a process for producing solifenacin from 2- (imidazolylcarbonyl)-1-phenyltetrahydroisoquinoline as a production starting material; (2) a process for producing solifenacin succinate from quinuclidin yl (1RS)-phenyltetrahydroisoquinolinecarboxylate as a production starting material; (3) a process for producing solifenacin from a lower- alkylquinuclidinyl carbonate as a production starting material; and (4) a process for producing solifenacin, comprising causing an alkali metal lower alkoxide to act on a secondary lower alkyl or tertiary lower alkyl phenyltetrahydroisoquinolinecarboxylate as a production starting material.