V. Thioanalogues of sparteine lactams. (C)-2-Thiono-17-oxosparteine and (C)-2,17-dithionosparteine

The X-ray and spectroscopic results clearly indicate that the (C)-2-thiono-17-oxosparteine (1) and (C)-2,17-ditihionosparteine (2) are conformationally rigid. In order to analyze deviations of lactam/thiolactam groups from planarity induced by ring constraints, the Dunitz– Winkler approach has been used. The lactam and thiolactam groups are close to planarity, only the lactam group in one of the two independent molecules of 1 is markedly non-planar. The bond angles in the thiolactam and lactam groups are highly diverse. Rings A and C adopt a distorted sofa conformation in both compounds. The distortions in the molecules of 2 as compared with those in the related monothiolactams correspond to the unusual chemical shifts of H5(eq), H5(ax) and H11, as well as to the extremely low J5ax-6 and extremely large J5eq-6 coupling constants. Also chemical shifts show a similar regularity being extremely high and low for C2 and C17, respectively. q 2004 Elsevier B.V. All rights reserved