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    Author(s): Frank R. Fronczek; Richard W. Hemingway; G. Wayne McGraw; Jan P. Steynberg; Carin A. Helfer; Wayne L. Mattice
    Date: 1993
    Source: Biopolymers 33(275-282
    Publication Series: Miscellaneous Publication
    PDF: View PDF  (1.8 MB)

    Description

    The structure of tetra-O-methyl-(+)-catechin has been determined in the crystalline state. Two independent molecules, denoted structure A and structure B, exist in the unit cell. Crystals are triclinic, space group P1, a=4.8125(2) Ǻ, b=12.9148(8) Ǻ, c=13.8862(11) Ǻ, α=86.962(6)°, β=89.120(5)°, γ=88.044(5)°, Ζ=2, De=1.336 g cm-3, R=0.033 for 6830 observations. The heterocyclic rings of the crystal structures are compared to previous results for 8-bromotetra-O-methyl-(+)-catechin, penta-O-acetyl-(+)-catechin, and (-)-epicatechin. One of the two molecules has a heterocyclic ring conformation similar to that observed previously for (-)-epicatechin, and the other has a heterocyclic ring conformation similar to one predicted earlier in a theoretical analysis of dimera of (+)-catechin and (-)-epicatechin. Both structure A and structure B in the crystal have heterocyclic ring conformations that place the dimethoxyphenyl substituent at C(2) in the equatorial position. However. this heterocyclic ring conformation does not explain the proton nmr coupling constant measured in solution. Molecular dynamics simulations show an equatorial- axial interconversion of the heterocyclic ring, which can explain the nmr results.

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    Citation

    Fronczek, Frank R.; Hemingway, Richard W.; McGraw, G. Wayne; Steynberg, Jan P.; Helfer, Carin A.; Mattice, Wayne L. 1993. Crystal structure, conformational analysis, and molecular dynamics of tetra-0-methyl-(+)-catechin. Biopolymers 33(275-282

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