Molecular Modeling of Lignin β-O-4 Model Compounds. Comparative Study of the Computed and Experimental Conformational Properties for a Guaiacyl β-O-4 Dimer
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S. Besombes
Summary
The conformational preferences of the threo and erythro diastereomeric forms of a guaiacyl β-O-4 dimer have been investigated by molecular modeling using the CHARMM force field. Many low energy conformations have been identified for each diastereomer, showing that β-O-4 dimers can adopt a large variety of shapes. A consistent structural model has emerged that indicates different conformational behavior for the threo and erythro forms, corresponding to a preferential extended overall shape for the threo form. All the low energy conformers are stabilized by intramolecular H-bonds. In particular, the highly directional H-bond between the α or γ hydroxyl hydrogen and the aromatic methoxy oxygen governs the B aromatic ring orientation. However, it has appeared that the conformational preferences are predominantly governed by local steric interactions rather than by differences in the H-bonding pattern. From the satisfactory agreement between computed data (geometries and the Boltzmann distribution of the low energy conformers) and the experimental data reported in the literature (X-ray crystal structures and 3JHαHβ NMR coupling constant), the CHARMM force field has been validated for the study of β-O-4 structures. Clearly, the molecular modeling calculations have led to an improved rationalization of the conformational data collected by experimental techniques.
Copyright © 2003 by Walter de Gruyter GmbH & Co. KG
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Artikel in diesem Heft
- Editorial
- Post-Harvest Chemical Staining in Blackwood (Acacia melanoxylon R. Br.)
- Albino Strains of Ophiostoma Species for Biological Control of Sapstaining Fungi
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