The a , a -dimethyl-β-lactam derivatives of 1,5-benzothiazepines were synthesized by the reaction of simple lithium ester enolates with 1,5-benzothiazepines. Their structure were characterized by elemental analysis, IR,~1H NMR and MS spectra. The crystal structure was determined by single-crystal X-ray diffraction analysis. The crystal of la belongs to triclinic system, space group PI, unit cell dimensions: a = 0.9299(3) nm, 6 = 1.0134(3) nm, c = 1.2455(4) ran, a= 98.457(5)°, β = 106.143(5)°,γ= 103.843(5)°, V= 1.0657(6) nm~3, Z = 2, D_c = 1.295Mg/m~3, F(000)=440,μ= 0.175 mn~(-1), R_1= 0.0406, Wr_2 = 0.1064.

Key words: benzothiazepine;ethyl isobutyrate;isopropyl isobutyrat, menthyl isobutyrate;ELEMENTAL ANALYSIS;IR;1HNMR;CRYSTAL STRUCTURE;XRD