Conformational Analysis of a New Cytochalasin Using Molecular Mechanics and Nuclear Magnetic Resonance Spectroscopic Data
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Date
1994-06
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Addis Ababa Universty
Abstract
This projeot uses moleoular mechanics teohniques with the
aid of NMR data to determine low-energy oonformations (threedimensional
structures) of a novel cytochalasin isolated from
fungus XYlaria Obovota[lj. Although the two-dimensional
struoture for this substituted hydrogenated isoindole unit
fused to an II-membered ring has been postulated, no study of
the three-dimensional struoture has been made.
Molecular mecanics teohniques, the force field equations,
and conformational searching algorithms: the stoohastic search
(random search method) on cartesian and internal coordinates
have been applied. A total of 22 conformations were generated
within 10 kcal/mol to the global minimum. The calculated proton
coupling constants, averaged over the first six lowest-energy
conformations, were compared with the experimental values. The
geometry parameters, the calculated coupling constants, the
structure of the isoindole unit, the macrocycle and overall
structure of the cytochalasin were also compared with similar
cytochalasins whose struotures were determined from x-ray and
related experimental techniques. Comparison of the calculated
coupling constants and the various torsion angles for this
novel fungal cytochalasin revealed similarity in the
conformations of the structures generated from the analysis and
those determined experimentally.
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Keywords
moleoular mechanics teohniques