Crystal structure of trans[1,5-Benzothiazepine-4(5H)-one-1-oxide-2,3-dihydro-3-hydroxy-2(4-methoxypheyl)](+). P.Kumaradhas and K.A.Nirmala, Department of Physics, Bangalore University, Bangalore-560 056, INDIA

The title compound is a drug intermediates of diltiazem. Diltazem belongs to the family of drugs commonly named as calcium channel blockers or calcium antagonist and is useful for the treatment of cardiac and coronary diseases. The structure of title compound, is takenup to understand the effect of the molecular geometry, conformation of the seven membered ring and the crystal packing. The colourless crystals were grown from ethonal at room temperature, and x-ray diffraction data was collected at All India Institute of Medical Sciences, New Delhi. Crystal Data: C₁₆H₁₅NO₄S, Space group P-1, Triclinic, a=7.721(4), b=8.695(2), c=11.347(9)Å, [[alpha]]=83.38(2)^deg. ß=79.79(6)^deg., [[gamma]]=81.38(2)^deg., V=737.7(8)ų, Z=2, [[lambda]]=1.5418Å, D_c=1.429 mg/³

The structure has been solved by direct method SHELXS-86 and refined by full matrix least-squares method to the final value of R=0.058 and wR=0.140. The seven membered ring is distorted showing twist boat conformation. The methoxy and hydroxy groups has torsion angle 61.5(4)Å that is gauche orientation. The carbonyl oxygen is pseudo-equatorial and methoxyphenyl group is axial to the seven membered ring. There are two intermolecular hydrogen bonding forming the dimers in the crystal. On the whole the crystal packing is stabilized by hydrogen bonding.