125136-15-4Relevant academic research and scientific papers
Spectroscopic Properties of Free Phenolic 4-Arylflavan-3-ols as Models for Natural Condensed Tannins
Zyl, Pieter W. van,Steynberg, Jan P.,Brandt, Edward V.,Ferreira, Daneel
, p. 1057 - 1063 (2007/10/02)
A unique range of free phenolic 4-arylflavan-3-ols consisting of four sets (3',4',5,7-tertrahydroxyflavan-3-ol or its 5-deoxy analogue coupled to phloroglucinol or resorcinol), each composed of three diastereomers (2,3-trans-3,4-trans, 2,3-trans-3,4-cis and 2,3-cis-3,4-trans) were synthesized to assess their spectroscopic properties. 1H and 13C NMR and circular dichroism data are related to selected structural and stereochemical features with a view to modelling natural phenolic oligoflavanoids. - Key words: 4-Arylflavan-3-ols 1H NMR 13C NMR Circular dichroism Condensed tannins
OLIGOMERIC FLAVANOIDS.PART 6.EVIDENCE SUPPORTING THE INVERSION OF ABSOLUTE CONFIGURATION AT 3-C ASSOCIATED WITH BASE CATALYSED A-/B-RING INTERCHANGE OF PRECURSORS HAVING 2,3-TRANS-3,4-CIS-FLAVAN-3-OL CONSTITUENT UNITS
Steynberg, Jan P.,Burger, Johann F. W.,Young, Desmond A.,Brandt, Edward V.,Ferreira, Daneel
, p. 923 - 935 (2007/10/02)
Whereas the enantiomeric 2,3-trans-3,4-trans-arylflavan-3-ols (10) and (12) as biflavanoid models are subject to stereospecific C-ring isomerisation under base catalysis, those with 3,4-cis configuration (11) and (13) are transformed stereoselectively via
Synthesis of Condensed Tannins. Part 2. Synthesis by Photolytic Rearrangement, Stereochemistry, and Circular Dichroism of the First 2,3-cis,3,4-cis-4-Arylflavan-3-ols
Westhuizen, Jan H. van der,Ferreira, Daneel,Roux, David G.
, p. 1220 - 1226 (2007/10/02)
Photolytic rearrangements of those 2,3-trans-3,4-trans- and 2,3-trans-3,4-cis-4-arylflavan-3-ols in which the nucleophilicity of D-ring (4-aryl group) functionality exceeds that of the A-ring, provide the first access to 2,3-cis-3,4-cis-diastereoisomers.The circular dichroism of these new isomers is at variance with the proposed general rule for assessing the absolute configuration at C-4.In terms of the aromatic quadrant rule such discrepancies correlate with deviations from the preferred C-ring conformations.
