PURPOSE: To obtain easily and economically the titled compound, by developing and eluting a racemic modification of a benzothiazepine derivative adsorbed in a column packed with an adsorbent containing a chiral large-ring polyether uniformly mixed therein to carry out the column chromatographic fractionation.

CONSTITUTION: A racemic modification of a benzothiazepine derivative expressed by formula I [R1 is H or COCH3; R2 is H or CH2CH2N(CH3)2] is subjected to the column chromatographic fractionation with an organic solvent, e.g. chloroform, as a developing agent using a previously set column packed uniformly with an adsorbent containing a chiral (S- or R-form) of a large-ring polyether (a crown compound) mixed therein to give the aimed substance optically active benzothiazepine derivative expressed by formula II.

USE: Useful as a coronary vasodilator, antidepressant, tranquilizer, etc. and further as a synthetic intermediate therefor.