Ring a conformation in steroids. 3—Cyclosteroids and cyclopropanosteroids†

Proton and carbon NMR data are provided for 21 ring A and ring B cyclosteroids and cyclopropano (or methylene) steroids. Shift assignments were made using standard 2D NMR techniques, while ring A proton subspectra were extracted with a 1D TOCSY experiment. Coupling constants were obtained from iterative spin system simulation of these sub-spectra. Ring A conformations were determined from the two- and three-bond proton-proton couplings and NOE measurements. The utility and limitations of extended Karplus-type equations, the effect of cyclopropyl groups on vicinal and geminal couplings and cyclopropane-induced chemical shifts are discussed.