The required 2-amino-5-methylthiophenol (III) was obtained by basic hydrolysis of the aminobenzothiazole (II), which was prepared from p-toluidine (I) and in situ generated thiocyanogen. Reaction of thiophenol (III) with the arylglycidic ester (IV) produced the racemic threo-amino ester (V). After basic hydrolysis of the ester group of (V), the resultant amino acid was resolved by means of D-(4-hydroxyphenyl)glycine methyl ester. The required amino acid enantiomer (VI) was then cyclized to lactam (VII) by heating in xylene with azeotropic removal of water. N-alkylation of benzothiazepinone (VII) with 2-(dimethylamino)ethyl chloride (VIII) provided (IX). The secondary alcohol of (IX) was esterified with acetic anhydride, and the resultant compound was finally isolated as the corresponding maleate salt.