Structure and nuclear magnetic resonance spectra of 6-bromo-3,3′,4′,5,7-penta-O-methylcatechin

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Abstract
The title compound has been synthesized by selective debromination of 6,8-dibromocatechin and indirect methylation of the resulting 6-bromocatechin via its pentaacetate. The structure of C20H23BrO6 has been determined by X-ray crystallography. The compound crystallizes in the space of group P1 with a = 9.589(3).ANG., b = 11.576(3).ANG., c = 11.326(3).ANG., .alpha. = 118.80(3).degree., .beta. = 93.23(3).degree., .gamma. = 111.44(3).degree., .rho.c = 1.481 g cm-3, and Z = 2. Intensities were measured for 2584 independent reflections (2.theta. < 45.degree.) of which 2213 were observed (I > 3.0.sigma.(I)) and used in subsequent refinement (final R values were R = 0.0268 and Rw = 0.0344). Crystallographic and pmr data confirm the position of the bromine atom at C-6, the tran-diaxial arrangement of H-2/H-3 and the quasi-equatorial orientation of the 3,4-dimethoxyphenyl group (ring B). The two heterocyclic ring conformations are consistent with the expected flexibility of the molecule.

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