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Crystal structure, conformational analysis, and molecular dynamics of tetra‐ O ‐methyl‐(+) ‐catechin
Author(s) -
Fronczek Frank R.,
Hemingway Richard W.,
Mcgraw G. Wayne,
Steynberg Jan P.,
Helfer Carin A.,
Mattice Wayne L.
Publication year - 1993
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.360330209
Subject(s) - chemistry , triclinic crystal system , crystal structure , ring (chemistry) , stereochemistry , crystallography , substituent , molecule , cyclohexane conformation , hydrogen bond , organic chemistry
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) Å, b = 12.9148(8) Å, c = 13.8862(11) Å, α = 86.962(6) °, β = 89.120(5)°, γ = 88.044(5)°, Z = 2, D c = 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 dimers 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. © 1993 John Wiley & Sons, Inc.