69127-07-7Relevant articles and documents
Oligomeric Flavonoids. Part 16. Novel Prorobinetinidins and the First A-Type Proanthocyanidin with a 5-Deoxy A- and 3,4-cis-C-Ring from the Maiden Investigation of Commercial Wattle Bark Extract
Cronje, Annemarie,Steynberg, Jan P.,Brandt, E. Vincent,Young, Desmond A.,Ferreira, Daneel
, p. 2467 - 2478 (2007/10/02)
Structural examination of the phenolic metabolites of commercially used wattle bark extract reveals the presence of a range of novel flavonoids comprising (-)-epirobinetinidol 1, the first C-methyl proanthocyanidin, (-)-fisetinidol-(4α,8)-6-methyl-(+)-catechin 3, the first prorobinetinidins with 3,4-cis-C-ring configurations 7 and 9, and the unique A-type prorobinetinidin 11 representing the first entry amongst this class of oligoflavonoids exhibiting a 5-deoxy A- and a 3,4-cis-C-ring.They are accompanied by a range of functionalized prorobinetinidin-type tetrahydropyranochromenes 20, 23, 25 and 28 and the trimeric 'isomerization-intermediate' 32, all exhibiting the characteristic structural features that are essential for the use of 'Mimosa' exctract in cold-setting adhesives and leather-tanning applications.In addition, evidence demonstrating that the dynamic A-E conformational equilibrium of flavan-3-ol moieties in condenced tannins may be influenced by external factors is presented.
Synthesis of Condensed Tannins. Part 17. Oligomeric (2R,3S)-3,3',4',7,8-Pentahydroxyflavans: Atropisomerism and Conformation of Biphenyl and m-Terphenyl Analogues from Prosopis glandulosa ('Mesquite')
Young, Esme,Brandt, Edward V.,Young, Desmond A.,Ferreira, Daneel,Roux, David G.
, p. 1737 - 1750 (2007/10/02)
(2R,3S)-2,3-trans-3',4',7,8-Tetrahydroxyflavan-3-ol , the predominant metabolite in the heartwood of Prosopis glandulosa, represents a putative precursor of a variety of oligomers, including conventional - and -biflavan-3-ols, a -1,3-diarylpropylflavan-3-ol, - and atropisomeric -biphenyl-type biflavan-3-ols, and -m-terphenyl-type triflavan-3-ols.Other participants in these condensations are mainly (+)-catechin, and also the flavan-3,4-diol analogue of (+)-mesquitol.Oligomeric structures were confirmed by biomimetic oxidative and acid-induced couplings, and by nuclear Overhauser effect difference spectroscopy.These applications enabled correction of previous structural assignments for atropisomeric -(+)-mesquitol-(+)-catechins and -bis--(+)-catechins, and determination of their conformations.
Synthesis of Condensed Tannins. Part 14. Biflavanoid Profisetinidins as Synthons. The Acid-Induced 'Phlobaphene'Reaction
Young, Desmond A.,Cronje, Annemarie,Botes, Adrienne L.,Ferreira, Daneel,Roux, David G.
, p. 2521 - 2528 (2007/10/02)
Free phenolic - and -2,3-trans-(-)-fisetinidol-(+)-catechin diastereoisomers of both 3,4-trans and 3,4-cis configuration, which serve as synthons for higher oligomers, are available in improved yields from direct condensation, and also via novel 6-iodo-(+)-catechin as an intermediate substrate.Acid-induced transformations of the predominant -all-trans isomer, illustrative of the well-known 'phlobaphene reaction' of condensed tannins, is shown to include ring-isomerization and fission of the inter-flavanoid bond, followed in the latter instance by the alternatives of anthocyanidin formation, positional rearrangement and self-condensation.
Synthesis of Condensed Tannins. Part 11. Intramolecular Enantiomerism of the Constituent Units of Tannins from the Anacardiaceae: Stoicheiometric Control in Direct Synthesis: Derivation of 1H Nuclear Magnetic Resonance Parameters Applicable to
Viviers, Phillip M.,Kolodziej, Herbert,Young, Desmond A.,Ferreira, Daneel,Roux, David G.
, p. 2555 - 2562 (2007/10/02)
Tannins from the heartwoods of Schinopsis spp. (quebracho) and Rhus spp.(karee) represent mutual condensation products of their associated precursors (2S,3R,4S)(-)-leucofisetinidin, (2R,3S)-(+)-catechin and, to a minor extent, (2R,3R)-(-)-epicatechin.The
Synthesis of Condensed Tannins. Part 4. A Direct Biomimetic Approach to - and -Biflavanoids
Botha, Jacobus, J.,Ferreira, Daneel,Roux, David G.
, p. 1235 - 1245 (2007/10/02)
The generation of flavanyl-4-carbo-cations from flavan-3,4-diols and their condensation with nucleophilic flavan-3-ols to form - and -biflavanoids at ambient temperatures and mildly acidic aqueous conditions apparently simulates the initial step in condensed tannin formation in a number of natural sources.The stereospecificity (or stereoselectivity) of the reaction is conditioned mainly by the 2,3-cis or 2,3-trans stereochemistry of the parent flavan-3,4-diol, but also by the nuclephilicity of the flavan-3-ol, and its regiospecific (or regioselective) course by steric factors arising from variation in substitution of the receptive A-ring of the flavan-3-ol.
