Synthetic proanthocyanidin

Geissman, T. A.; Yoshimura, N.N.

doi:10.1016/s0040-4039(00)62004-x

Cited by 61 publications

(37 citation statements)

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“…When the very first proanthocyanidin oligomers were synthesized using native catechin units11 it quickly became apparent that protection of the phenolic functionalities was essential in order to achieve some regioselective control of the interflavan bond. Such protection is commonly achieved by using methyl,12 acetyl13 or benzyl14 groups.…”

Section: Resultsmentioning

confidence: 99%

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

Tarascou¹,

Barathieu²,

André³

et al. 2006

Eur J Org Chem

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A direct and general synthesis of procyanidin dimers B1, B2, B3 and B4 (10a-d) is presented. The approach is based on the stoichiometric coupling of two protected monomeric units (the nucleophilic 2a-b and electrophilic 4a-b partners) and deals with the regio-and stereocontrol of the C4-C8 interflavan bond as well as the control of the degree of oligomerization. The synthesis involves a five-step pathway starting from

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Section: Resultsmentioning

confidence: 99%

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

Tarascou¹,

Barathieu²,

André³

et al. 2006

Eur J Org Chem

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“…Ever since the isolation and structure elucidation of the first dimeric procyanidins by Weinges et al (1) and their first synthesis (2,3), unambiguous determination of the position of the interflavanoid linkage, i.e., the carbon atom of ring A of the terminal catechin or epicatechin unit (C-6 or C-8) that is bonded to C-4 of a second flavanoid, has remained problematic. This applies even to simple monoflavanoids such as monobromotetra-and penta-0-methylcatechin, for which Weinges (1,3) postulated the 8-bromo structure on the basis of the greater steric accessibility of C-8 relative to C-6 in electrophilic aromatic substitution.…”

Section: Introductionmentioning

confidence: 99%

Proton magnetic resonance spectra of catechin and bromocatechin derivatives: C₆- vs. C₈-substitution

Kiehlmann¹,

Tracey²

1986

Can. J. Chem.

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The 1Hmr spectra of 20 catechin derivatives substituted at C-6/C-8 by bromine and/or hydrogen and at oxygen by methyl, acetyl, and/or hydrogen have been analyzed in deuterated acetone, acetonitrile, and chloroform. Because of its dependence on the nature of the solvent and of the oxygen substituent, the difference between H-6 and H-8 chemical shifts has been found to be an unreliable criterion for the distinction between 8-bromo and 6-bromo isomers. In methylated catechins, double irradiation of H-8 and H-6 enhances one (MeO-7) and two (MeO-5 and MeO-7) methoxy signals, respectively, via the nuclear Overhauser effect. This permits unambiguous assignment of chemical shifts to all ring A protons. The H-6 and H-8 resonance frequencies of catechin have been determined by decoupling of the OH-5 and OH-7 protons.

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“…(−)‐Epicatechin and (+)‐catechin were purchased from Aldrich (Steinheim, Germany). Procyanidin dimers B3, B6, B4 and B8,32, 33 dimers B1, B2, B5 and B7, trimer C1 and esters (−)‐epicatechin‐3‐ O ‐gallate and B2‐3″‐ O ‐gallate33 were extracted from grape ( Vitis vinifera ) seeds and purified as described elsewhere.…”

Section: Methodsmentioning

confidence: 99%

A colorimetric study of oenin copigmented by procyanidins

Berké

Freitas

2006

J Sci Food Agric

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A colorimetric method was used to analyse the influence of procyanidin structure on colour changes of malvidin 3-O-glucoside (oenin) solution resulting from copigmentation. The study was performed in hydroalcoholic citrate/phosphate buffer solution (120 g L −1 ) at pH 3.6 and ionic strength 0.2 mol L −1 . Chromatic L * , a * and b * coordinates (CIELAB, D65/10 • illuminant/observer condition) obtained from spectral curves recorded between 360 and 830 nm allowed the calculation of lightness L * , chroma C * and hue angle h ab . In general, addition of copigment induced colour enhancement (loss of lightness and increased chroma). The prevailing parameters affecting colour changes were lightness and chroma for monomers and lightness and hue for procyanidins B5 and B8 (C4-C6 dimers). A small blueing effect was observed only for catechin monomer-copigmented solutions. For procyanidin copigments, as the structural complexity of the copigment increased, the hue angle moved to yellower values. The ester gallate of dimer B2 produced the strongest modification of colour attributes of oenin solution. INTRODUCTIONChanges in anthocyanin and tannin composition are involved in the evolution of red wine colour. Purple tints of young red wines decline to a tilelike orange colour in mature wines. These colour changes result from the formation of more stable pigments during aging. Over the last few years, several groups of anthocyanin-derived pigments with different colours have been identified in red wines, namely vinyl-phenol derivatives of anthocyanins 1,2 and anthocyanin-pyruvic acid adducts, 3 -5 which have a brick-red colour, as well as compounds resulting from acetaldehyde-mediated condensation between anthocyanins and flavanols, e.g. ethyl bridge adducts with a purple colour, 6 -10 orange pyranoanthocyanin-flavanol pigments 11 and vinylpyranoanthocyanin-flavanols (portisins) with a blue colour. 12 -17 Colour expression of anthocyanin pigments also relies on copigmentation. Effectively non-covalent interactions of anthocyanins and wine constituents make an important contribution to red wine colour. 18 -21 Copigmentation of anthocyanins is responsible for variations in absorbance (hyperchromic shift) and increases the maximum absorption wavelength in the visible region (bathochromic shift). However, differences in the absorption spectrum are observed not only at λ max of the flavylium ion but also over the full range of visible wavelengths. The accurate description of colour should refer to lightness (L * ),

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Synthetic proanthocyanidin

Cited by 61 publications

References 1 publication

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

Proton magnetic resonance spectra of catechin and bromocatechin derivatives: C₆- vs. C₈-substitution

A colorimetric study of oenin copigmented by procyanidins

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Synthetic proanthocyanidin

Cited by 61 publications

References 1 publication

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

An Improved Synthesis of Procyanidin Dimers: Regio‐ and Stereocontrol of the Interflavan Bond

Proton magnetic resonance spectra of catechin and bromocatechin derivatives: C6- vs. C8-substitution

A colorimetric study of oenin copigmented by procyanidins

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Proton magnetic resonance spectra of catechin and bromocatechin derivatives: C₆- vs. C₈-substitution