Open AccessConformational analysis of 9β,19-cyclopropyl sterols: Detection of the pseudoplanar conformer by nuclear Overhauser effects and its functional implications
Author(s) -
W. David Nes,
Mabry Benson,
Robert E. Lundin,
Phu H. Le
Publication year - 1988
Publication title -
proceedings of the national academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.85.16.5759
Subject(s) - conformational isomerism , chemistry , nuclear overhauser effect , lanosterol , stereochemistry , cyclohexane conformation , nuclear magnetic resonance spectroscopy , crystallography , bent molecular geometry , two dimensional nuclear magnetic resonance spectroscopy , molecular conformation , sterol , molecule , cholesterol , organic chemistry , biochemistry , hydrogen bond
Nuclear Overhauser difference spectroscopy and variable temperature studies of the 9β,19-cyclopropyl sterols 24,25-dehydropollinastanol (4,4-desmethyl-5α-cycloart-24-en-3β-ol) and cyclolaudenol [(24S )-24-methyl-5α-cycloart-25(27)-en-3β-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 9β,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.
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