An unusual reaction of flavan-3-ols with acetone of relevance to the formation of the tetracyclic ring system in peltogynoids
作者:Jan H. Van Der westhuizen、Jacobus A. Steenkamp、Daneel Ferreira
DOI:10.1016/s0040-4020(01)90082-1
日期:1990.1
Flavan-3-ols are in moist acetone subject to acid-catalyzed incorporation of an 1-methylethylidene fragment between 3-OH and C-2 (B-ring) to give a tetracyclic ring system reminiscent of the peltogynoid series of flavonoids.
Tyrosinase catalysed biphenyl construction from flavan-3-ol substrates
作者:Werner Janse van Rensburg、Daneel Ferreira、Elfranco Malan、Jacobus A. Steenkamp
DOI:10.1016/s0031-9422(99)00476-8
日期:2000.1
Mushroom tyrosinase catalysed oxidation of three flavan-3-ols, viz. catechin, fisetinidol and mesquitol, was conducted to construct biphenyl bonds. Exposure of the flavan-3-ols to tyrosinase and subsequent trapping of the o-quinone intermediates resulted in the formation of novel flavan-3-ol derivatives, the structures of which were elucidated by mono- and two-dimensional 1H-NMR experiments. Application of the methodology resulted in the improved synthesis of the natural flavan-3-ol dimer, mesquitol-[5-->8]-catechin, previously isolated from Prosopis glandulosa.
Unusual amount of (−)-mesquitol from the heartwood of <i>Prosopis juliflora</i>
A large amount of flavonoid has been extracted and isolated from the heartwood of Prosopis juliflora, an exogenous wood species of Kenya. Structural and physicochemical elucidation based on FTIR, 1H and 13C NMR, GC-MS and HPLC analysis clearly demonstrated the presence of (-)-mesquitol as the sole compound without any noticeable impurities. The product was able to slow down oxidation of methyl linoleate induced by AIBN. The important amount and high purity of (-)-mesquitol present in the acetonic extract of P. juliflora could therefore be of valuable interest as a potential source of antioxidants from a renewable origin.
Brandt, E. Vincent; Young, Desmond A.; Young, Esme, Journal of the Chemical Society. Perkin transactions II, 1987, p. 1365 - 1368
作者:Brandt, E. Vincent、Young, Desmond A.、Young, Esme、Ferreira, Daneel
DOI:——
日期:——
Young, Desmond A.; Young, Esme; Roux, David G., Journal of the Chemical Society. Perkin transactions I, 1987, p. 2345 - 2352
作者:Young, Desmond A.、Young, Esme、Roux, David G.、Brandt, E. Vincent、Ferreira, Daneel