PURPOSE: To obtain an optically active benzothiazepine derivative easily and economically, by subjecting directly a racemic benzothiazepine derivative to optical resolution by column chromatography using chemically modified 3-aminopropyl silica.

CONSTITUTION: A racemic modification of a benzothiazepine derivative shown by the formula I [R1 is H, or COCH3; R2 is H, CH2CH2N(CH3)2, etc.] is subjected to optical resolution by column chromatography using chemically modified (condensed with an N-acyl derivative of L-amino acid) 3-aminopropyl silica, to give an optically active benzothiazepine derivative shown by the formula II.

USE: A coronary vasodilator, antidepressant, and tranquilizer.