Related Experiment Video
Updated: Aug 9, 2026

Structure-Guided Design and Development of Novel Cyclophilin A Inhibitors and Ganoderiol-F Derivatives: An In-Silico Approach
Published on: June 23, 2026
Conformational analysis of 9beta,19-cyclopropyl sterols: Detection of the pseudoplanar conformer by nuclear
W D Nes1, M Benson, R E Lundin
1Plant and Fungal Lipid Group, Plant Physiology Research Unit, Russell Research Center, U.S. Department of Agriculture, Athens, GA 30605.
Abstract:
Nuclear Overhauser difference spectroscopy and variable temperature studies of the 9beta,19-cyclopropyl sterols 24,25-dehydropollinastanol (4,4-desmethyl-5alpha-cycloart-24-en-3beta-ol) and cyclolaudenol [(24S)-24-methyl-5alpha-cycloart-25(27)-en-3beta-ol] have shown the solution conformation of the B/C rings to be twist-chair/twist-boat rather than boat/chair as suggested in the literature. This is very similar to the known crystal structure conformation of 9beta,19-cyclopropyl sterols. The effect of these conformations on the molecular shape is highly significant: the first conformation orients into a pseudoplanar or flat shape analogous to lanosterol, whereas the latter conformation exhibits a bent shape. The results are interpreted to imply that, for conformational reasons, cyclopropyl sterols can be expected to maintain the pseudoplanar shape in membrane bilayers.
Related Concept Videos
Stereoisomerism of Cyclic Compounds
¹H NMR of Conformationally Flexible Molecules: Temporal Resolution
Stability of Substituted Cyclohexanes
The two chair conformations of cyclohexanes undergo rapid interconversion at room temperature. Both forms have identical energies and stabilities, each comprising equal amounts of the equilibrium mixture. Replacing a hydrogen atom with a functional group makes the two conformations energetically non-equivalent.
For example, in...
Conformations of Cycloalkanes
¹H NMR of Conformationally Flexible Molecules: Variable-Temperature NMR
Chair Conformation of Cyclohexane
The hydrogen atoms linked to carbons are arranged in two different axial and equatorial orientations to achieve this staggered...

