PROCESS FOR PRODUCING OPTICALLY ACTIVE DIHYDROPYRIDINEPHOSPHONIC ESTER

摘要

[PROBLEMS] To provide a process for efficiently producing an optically active isomer of efonidipine, the isomer being useful as an antihypertensive agent or a therapeutic agent for angina pectoris. [MEANS FOR SOLVING PROBLEMS] The process, which is for producing an optically active isomer of the compound represented by the formula (1), [Chemical formula 1] (1) is characterized in that a racemate of the compound represented by the formula (1) is dissolved in a solvent to prepare a supersaturated solution and crystals of one of the optically active isomers of the compound represented by the formula (1) are added as seed crystals to the supersaturated solution to precipitate crystals of the optically active isomer whose seed crystals were added, or that a mixture of optically active isomers of the compound represented by the formula (1) in which either of the isomers is present in excess is dissolved in a solvent to prepare a supersaturated solution and crystals of the optically active isomer which is present in excess are added as seed crystals to the supersaturated solution to precipitate crystals of the optically active isomer present in excess.