- Oligomeric flavanoids. Part 19. Reductive cleavage of the interflavanyl bond in proanthocyanidins
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The interflavanyl bond in profisetinidins 1, 4 and 6, and methyl ethers 3, 5, 28 and 29 procyanidins 24 and 26, and their methyl ethers 25 and 27 is readily subject to cleavage with sodium cyanoboranuide in trifluoroacetic acid at 0 deg C.This method will contribute significantly to the structure elucidation of the 5-deoxy (A-ring) proanthocyanidins from important commercial sources.Boltzmann-averaged heterocyclic ring coupling constants as determined by a conformational global search routine (GMMX) and NOE difference spectroscopy were used to assign unequivocally the diastereotopic methylene protons in the 1H NMR spectra of flavan-3-ols, a prerequisite for corroboration of the cleavage mechanism.
- Steynberg, Petrus J.,Steynberg, Jan P.,Bezuidenhoudt, Barend C. B.,Ferreira, Daneel
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p. 3005 - 3012
(2007/10/03)
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- Cleavage of the Interflavanyl Bond in 5-Deoxy (A Ring) Proanthocyanidins
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The fisetinidol-(4,8) and (4,6)-catechin profisetinidin biflavonoids 1, 4 and 5 respectively, are subject to facile cleavage of the interflavanyl linkage with sodium cyanoborohydride in trifluoroacetic acid at 0 deg C.
- Steynberg, Petrus J.,Steynberg, Jan P.,Bezuidenhoudt, Barend C. B.,Ferreira, Daneel
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