Condensed tannins. 19. Configuration of diol groups in flavan-3,4-diols by paper chromatography and paper ionophoresis

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Abstract
The chromatographic behavior on paper impregnated with aqueous [image]-sodium borate, and the paper-ionophoretic mobility in the same solvent, of geometrical isomers of methylated flavan-3,4-diols of known relative configuration were examined. Isomers of 3,4-cis-diol configuration had lower RF values than those of the 3,4-trans-diol arrangement, and only the former group showed positive ionophoretic mobility. The degree of positive mobility might be of structural significance. These simple methods, although standarized against a limited range of compounds, appeared useful for establishing the purity of geometrical isomers, and for differentiating between 3,4-cis- and 3,4-trans-diol arrangements. Racemic 3'',4'', 5'',7-tetramethoxy -2,3-cis-flavan-3,4-cis-diol, 3'', 4'',7-trimethoxy-2,3-cis-flavan-3,4-cis-diol, 3'',4'',5'',7-tetramethoxy- 2,3-cis-flavan-3-ol and their acetates were synthesized, and their stereochemistry confirmed by nuclear-magnetic-resonance spectroscopy.