Barend C. B. Bezuidenhoudt
University of Cambridge
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Featured researches published by Barend C. B. Bezuidenhoudt.
Phytochemistry | 1987
Barend C. B. Bezuidenhoudt; E. Vincent Brandt; Daneel Ferreira
Abstract Two novel pterocarpans, 8-hydroxy-3,9-dimethoxy- and 3,8-dihydroxy-9-methoxypterocarpan and a new santal analogue were isolated from the heartwood of P. soyauxii. These are accompanied by several known pterocarpans, isoflavans, isoflavones and trans-pterostilbene. From the heartwood of P. marsupium were obtained 8-C-β- d -glucopyranosyl-3,7,4′-trihydroxy- and -3,7,3′,4′-tetrahydroxyflavone, representative of the first 5-deoxy C-C-coupled flavonol glucosides, and the rare 3′-C-β- d -glucopyranosyl-α-hydroxydihydrochalcone, their structures being determined by means of high resolution NMR techniques.
Tetrahedron Letters | 1987
Barend C. B. Bezuidenhoudt; Annelie Swanepoel; Jan A.N. Augustyn; Daneel Ferreira
Epoxidation of 4-methoxy-2′,4′-dimethoxymethyl-(E)-chalcone with H2O2 in the presence of poly-α-aminoacid catalysts afforded chiral aromatic oxygenated chalcone epoxides. These were transformed into the corresponding α-hydroxydihydrochalcones and their absolute configurations determined by c.d. spectroscopy. One of these was proved to be identical to a novel αR-analogue from Pericopsis elata.
Tetrahedron Letters | 1992
Pieter S. van Heerden; Barend C. B. Bezuidenhoudt; Jacobus A. Steenkamp; Daneel Ferreira
Abstract Several benzylic copper reagents, BnCu(CN)MgCl, Bn 2 CuMgCl, BnCu-TMSCl-HMPA, and BnCu-TMSCl-TMEDA, facilitate the conjugate addition of the benzyl ligand to α,β-enones, but only BnCu-TMSCl-TMEDA gave high yields with α,β-unsaturated esters.
Tetrahedron Letters | 1990
Petrus J. Steynberg; Johann F. W. Burger; Barend C. B. Bezuidenhoudt; Jan P. Steynberg; Martha S. Van Dyk; Daneel Ferreira
Abstract The functionalized 2,3- trans -8,9- trans -9,10- cis -3,4,9,10-tetrahydro-2 H ,8 H -pyrano[2,3- h ]chromenes 4 and 6 represent the first naturally occurring condensed tannins with (2 S ,3 R )-2,3- trans -(−)-catechin ‘terminal’ moieties; the structure of 4 is unequivocally confirmed by synthesis.
Phytochemistry | 1988
S.Catherine Bezuidenhout; Barend C. B. Bezuidenhoudt; Daneel Ferreira
Abstract In addition to some previously described 7,8-dioxy-isoflavonoids and 2-benzylbenzo[ b ]furan-3 (2H)-ones the heartwood of Xanthocercis zambesiaca has been shown to contain 7,8,3′-trihydroxy-4′-methoxyisoflavone. These are accompanied by the novel α,3,4,4′-tetrahydroxy-2′-methoxydihydrochalcone and its 3-deoxy analogue, the latter of which presumably served as biogenetic precursor for the unique 1-hydroxy-3-(4-hydroxyphenyl)-1-(4-hydroxy-2-methoxyphenyl) propan-2-one and its 1-deoxy analogue. Such possible biosynthetic relationship was demonstrated by the facile in vitro transformations of the appropriate α-hydroxydihydrochalcone into the different 1,3-diarylpropan-2-ones.
Tetrahedron Letters | 1994
Barend C. B. Bezuidenhoudt; Grant H. Castle; Joanna V. Geden; Steven V. Ley
Abstract Highly selective, asymmetric, Lewis acid catalysed Diels-Alder reactions are reported with a bifunctional, C 2 -symmetrical diacrylate derivative obtained from a chiral auxiliary based on dihydroxylated dispiroketals.
Tetrahedron | 1990
C. Hendrik; L. Mouton; Jacobus A. Steenkamp; Desmond A. Young; Barend C. B. Bezuidenhoudt; Daneel Ferreira
Abstract The phenolic methyl ethers of flavan-3-ols, 4-arylflavan-3-ols, and (-)-fisetinidol-(4,8)-( + )-catechin biflavanoids are susceptible to regio- and stere- oselective hydroxylation at C-4 in moderate to high yields with potassium persul- phate/cupric sulphate in aqueous acetonitrile. The resultant 4-functionalized analogues are of both synthetic and degradative significance in condensed tannin chemistry.
Tetrahedron Letters | 1994
Barend C. B. Bezuidenhoudt; Grant H. Castle; Steven V. Ley
Abstract A range of rigid, architecturally complex diols derived from dispiroketals have been synthesised. A bifunctional, C2-symmetrical chiral auxiliary derived from these diols can be used in asymmetric synthesis.
ChemInform | 1992
Daneel Ferreira; Jan P. Steynberg; Johann F. W. Burger; Barend C. B. Bezuidenhoudt
The chemistry of condensed tannins at alkaline pH is regulated by the formation of A- and/or B-ring quinone-methides as highly reactive intermediates. The former group of electrophilic species is of special significance in analogues with 5,7-dihydroxy A-ring functionality and may be successfully trapped by external nucleophiles such as phenolic nuclei and thiols. B-ring quinone-methides may similarly be trapped but are preferentially susceptible to intramolecular trapping to give analogues with rearranged pyran heterocycles. A mechanistic rationale to explain the base-catalyzed rearrangement reactions and the oxidative conversion of B- to A-type proanthocyanidins is proposed. These reactions are of relevance to the industrial application of condensed tannins.
Journal of The Chemical Society-perkin Transactions 1 | 1988
Barend C. B. Bezuidenhoudt; E. Vincent Brandt; Jacobus A. Steenkamp; David G. Roux; Daneel Ferreira
The structure and stereochemistry of a novel [2,3′]-isoflavone-isoflavan oligomer, 2′,7-dihydroxy-2-[(3S)-6′,7-dihydroxy-4′-methoxyisoflavan-3′-yl]-4′-methoxyisoflavone (1; R = H), from Dalbergia nitidula are established by synthesis. The strategy of condensation of a C16 to C14 moiety, i.e. C-5′ formylated isoflavan (21) to a 2-hydroxydeoxybenzoin (23) in a modified Baker-Venkataraman approach, should provide general access to this novel class of C-2 coupled oligomeric Isoflavonoids.