Abstract: The structures of two derivatives of the title compound [C₂₄H₂₂N₂OS, M_r= 386. 5 for (1); C₂₅H₂₂N₂O₃S, M_r= 430. 5 for (2)] were determined by using X-ray single-crystal strcuture analysis method. The final discrepancies are R=0. 071 and 0. 077, respectively, for the reflections measured on a four-circle diffractometer. The space group for compound (1) is Pbca with a=1. 6639(4), b=2.0286(3), c= 1.1742(1) nm, V=3. 964(1) nm³, F(000)=1632e, Z=8; and (2) belongs to P2₁/n space group, and the cell dimensions are a=1. 1115(4), b=0. 8932(7), c=2. 186(3) nm, β=97. 52 (1)°, V=2.151(4) nm³, F(000)=904 e, Z=4.The molecular backbones are very similar, each is a tricyclic system. The central seven-membered ring is in a twisted-boat conformation, and is cis-fused to 1,2,4-oxa-diazolino ring, while the latter moiety is in an envelope form. There are conjugated but non-coplanar effects in each structure. All bond lengths and angles in the molecules are normally acceptable. The crystal structure on the whole is completely stabilized by Van der Waals interactions.

Key words: Crystal structure, Molecular structure, Benzothiazepine