Process for producing optically active dihydropyridinephosphonic ester

摘要

There is provided a process for efficiently producing an optically active substance of efonidipine that is useful as an antihypertensive agent or a therapeutic agent for angina pectoris. A process for producing an optically active substance of compound of formula (1) characterized by comprising: dissolving a racemate of the compound of formula (1) in a solvent to prepare a supersaturated solution; and adding crystal of either one optically active substance of the compound of formula (1) as a seed crystal in the supersaturated solution to allow crystal of the one optically active substance added as the seed crystal to separate out; or dissolving a mixture of the compound of formula (1) in which either one optically active substance thereof is present in excess in a solvent to prepare a supersaturated solution; and adding crystal of the one optically active substance present in excess as a seed crystal in the supersaturated solution to allow crystal of the one optically active substance present in excess to separate out.