69082-83-3Relevant academic research and scientific papers
Oligomeric flavanoids. Part 26. Structure and synthesis of the first profisetinidins with epifisetinidol constituent units
Steynberg, Petrus J.,Steynberg, Jan P.,Brandt, E. Vincent,Ferreira, Daneel,Hemingway, Richard W.
, p. 1943 - 1950 (2007/10/03)
The natural occurrence of the first oligomeric profisetinidins with (2R,3R)-2,3-cis-epifisetinidol chain extender units is demonstrated in the bark of Pithecellobium dulce (Guamuchil). Semi-synthesis using the appropriate flavan-3-ol and flavan-3,4-diol precursors permits unequivocal structural and stereochemical assignment of the novel dimeric epifisetinidol-(4β,8)-catechin and epicatechins 16 and 18, the trimeric bis-epifisetinidol-(4β,6:4β,8)-catechin and epicatechins 33 and 35, the fisetinidol-(4α,8)-catechin-(6,4β)-epifisetinidol 37 and fisetinidol-(4α,8)-epicatechin-(6,4β)-epifisetinidol 39.
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 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 5. The First Angular -Triflavanoids and Their Natural Counterparts
Botha, Jacobus J.,Vivers, Phillip M.,Young, Desmond A.,Preez, I. Cornelius du,Ferreira, Daneel,et al.
, p. 527 - 533 (2007/10/02)
Angular triflavanoids comprising a group of four diastereoisomeric -bi--(+)-catechins with definable absolute configurations (2R,3S,4S-and 2R,3S,4R-2R,3S-2R,3S,4S; 2R,3S,4S- and 2R,3S,4R-2R,3S-2R,3S,4R) result from flavanyl-4-carbocation mediated condensation of (2R,3S,4R)-flavan-3,3',4,4',7-pentaol at C-6 of the (+)-catechin units of all-trans-(2R,3S,4S-2R,3S)--(-)-fisetinidol-(+)-catechin and its 3,4-cis-(2R,3S,4R-2R,3S) diastereomer respectively.The natural coexistence of some of the forementioned species of bi- and tri-flavanoids and their precursors indicate a comparable sequence of 4,8 preceding 4,6 condensation with (+)-catechin as common nucleophile.
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.
