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

We have assayed 4,5-cyclopropanocholestan-3-ols and 4,5-cyclopropanocholestan-3-ones and tested them as substrates and inhibitors of cholesterol oxidase. The 4,5-cyclopropanocholestan-3/3-ols (α and β) are substrates of cholesterol oxidase that are converted to their respective ketones 1000-fold more slowly than cholesterol. The induced ring-current effects of a cyclopropane ring are clearly illustrated in the ¹H NMR spectra of these sterols. These shielding effects are dramatic because of the rigidity of the steroid backbone. Assignments of the ¹H resonances of the A, B, and cyclopropyl rings of the sterols have been made using DQF-COSY and NOESY experiments. We have assigned the upfield multiplet at approximately 0.5 ppm to H_6α in both isomers. H_6α is shielded by the cyclopropyl σ bond. H_6β is deshielded by the cyclopropane ring and appears at approximately 2.0 ppm in both isomers.