Ring a conformation in steroids. 3—Cyclosteroids and cyclopropanosteroids

Abstract

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, whie 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 protoeproton couplings and NOE measurements. The utility and limitations of extended Karplus-type equatioas, the effect of cyclopropyl groups on vicinal and geminal couplings and cyclopropane-induced chemical shifts are discUSSed.

4,5-Cyclopropanocholestan-3β-ol Substrates for Cholesterol Oxidase and Their 1H NMR Assignments

“…The calculated chemical shifts agree with those observed. Similar long range upfield and downfield shifts have been reported for other cyclopropyl steroids. − …”

NMR study of conformation and configuration in C‐20‐substituted 5β,14β‐pregnanes, 5β‐pregn‐14‐enes and 21‐nor‐5β,14β‐pregnanes

“…and (F). In[11][12][13][14][15][16] there is no possibility of hydrogen bonding between the C-20 substituent and the C-14 hydroxyl, making the conformers with H-20 over ring D preferred for steric reasons.17fl-Nitromethyl-l4-hydroxy-3fl-(a-~pyranorhamnosyl)oxy-5fl,l4fl-androstane (17) and 17fl-hydroxymethyl-l4-hydroxy-3fl-(a-~pyranorhamnosyl)oxy-5fl, 14fl-androstane (1 8) (21-norpregnanes) (Scheme 2)In 17, one of the C-20 protons has an anti coupling of 10.3 Hz to H-17, while the other H-20 proton has a gauche coupling of 5.3 Hz. The geminal coupling between the two C-20 protons is -12.5 Hz.…”