Synthesis of high molecular mass condensed tannin by cationic polymerization of flavan 3,4-carbonate

Yoneda, Satoshi; Kawamoto, Hiroyuki; Nakatsubo, Fumiaki

doi:10.1039/a606783b

Cited by 26 publications

(9 citation statements)

References 12 publications

(9 reference statements)

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“…Another main procedure for procyanidins synthesis is Lewis acid activation, which includes trimethylsilyl trifluoromethanesulfonate (TMSOTf), AgBF 4 and TiCl 4 for (-)-epicatechin and (+)-catechin dimmer, SnCl 4 and BF 3 ·Et 2 O for (+)-catechin oligomer, etc [ 45 , 46 , 47 ]. Usually, as a result of Lewis acid activation, a hydroxyl group at the C4 position is first formed in the derivatives of flavan-3-ols, which could be used as the electrophiles.…”

Section: Chemical Synthesis Of Proanthocyanidinsmentioning

confidence: 99%

“…Besides the synthesis of procyanidin oligomers, the condensed tannins with high molecular mass were obtained by the cationic polymerization of 3’,4’,5,7-tetrabenzyloxyflavan 3,4-carbonate and subsequent debenzylation, as shown in Scheme 8 . Using this strategy, a series of PAs with high molecular mass (the highest average molecular mass: 10,200) and high degree of polymerization (the highest degree of polymerization was 35) were synthesized, which could be used as model compounds for natural condensed tannins [ 47 ].…”

Section: Chemical Synthesis Of Proanthocyanidinsmentioning

confidence: 99%

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Chemical Synthesis of Proanthocyanidins in Vitro and Their Reactions in Aging Wines

Pan

Shi

et al. 2008

Molecules

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Proanthocyanidins are present in many fruits and plant products like grapes and wine, and contribute to their taste and health benefits. In the past decades of years, substantial progresses has been achieved in the identification of composition and structure of proanthocyanidins, but the debate concerning the existence of an enzymatic or nonenzymatic mechanism for proanthocyanidin condensation still goes on. Substantial attention has been paid to elucidating the potential mechanism of formation by means of biomimetic and chemical synthesis in vitro. The present paper aims at summarizing the research status on chemical synthesis of proanthocyanidins, including non-enzymatic synthesis of proanthocyanidin precursors, chemical synthesis of proanthocyanidins with direct condensation of flavanols and stereoselective synthesis of proanthocyanidins. Proanthocyanidin-involved reactions in aging wines are also reviewed such as direct and indirect reactions among proanthocyanidins, flavanols and anthocyanins. Topics for future research in this field are also put forward in this paper.

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Section: Chemical Synthesis Of Proanthocyanidinsmentioning

confidence: 99%

Section: Chemical Synthesis Of Proanthocyanidinsmentioning

confidence: 99%

Chemical Synthesis of Proanthocyanidins in Vitro and Their Reactions in Aging Wines

Pan

Shi

et al. 2008

Molecules

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“…Polyphenols are ingredients of agricultural products such as wine, tea, fruit, vegetables, and herbal medicines and play an important role due to their various biological functions 1. The specific interactions of polyphenolic compounds with proteins have stimulated the search for new drugs derived from them 2.…”

Section: Introductionmentioning

confidence: 99%

Stereoselective Synthesis of Benzylated Prodelphinidins and Their Diastereomers with Use of the Mitsunobu Reaction in the Preparation of Their Gallocatechin Precursors

Krohn¹,

Ahmed²,

John³

et al. 2010

Eur J Org Chem

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The tetrabenzylated catechin 9 was prepared by benzylation of the commercially available pure (+)‐catechin (3) and coupled with the commercially unavailable pentabenzylated(–)‐gallocatechin 10, prepared in a one‐step Mitsunobu‐type cyclization of the triol 8. The highly stereoselective synthesis of benzylated prodelphinidins – catechin‐(4α→8)‐gallocatechin (13), gallocatechin‐(4α→8)‐gallocatechin (14), and gallocatechin‐(4α→8)‐catechin (15) – is reported for the first time. The ESI(+)‐CID mass spectra of the coupling products were found to feature regioselective retro‐Diels–Alder (RDA) reactions and unusual sequential losses of pairs of C7H7· radicals (182 u) from the Na+ adduct ions.

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“…Thus TiCl 4 , AgBF 4 , SnCl 4 , TMSOTf have all been used to synthesize dimeric and oligomeric procyanidins of (+)-catechin and (-)-epicatechin units [29,[30][31][32][33][34][35][36]. In these reactions, the role of Lewis acids is to promote the formation of the benzylic carbocation at C4 of a flavanol subunit starting from a C4 hetero substituted flavanol, which thereafter undergoes a Friedel-Craft-like addition on a second flavanol subunit.…”

Section: Lewis Acid Induced Flavanol Couplingsmentioning

confidence: 99%

Flavonoids: Hemisynthesis, Reactivity, Characterization and Free Radical Scavenging Activity

2007

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Phenolic compounds form one of the main classes of secondary metabolites. They display a large range of structures and they are responsible for the major organoleptic characteristics of plant-derived-foods and beverages, particularly color and taste properties and they also contribute to the nutritional qualities of fruits and vegetables. Phenolic compounds are also highly unstable compounds which undergo numerous enzymatic and chemical reactions during postharvest food storage and processing thus adding to the complexity of plant polyphenol composition. Among these compounds flavonoids constitute one of the most ubiquitous groups of all plant phenolics. Owing to their importance in food organoleptic properties and in human health, a better understanding of their structures, their reactivity and chemical properties in addition to the mechanisms generating them appears essential to predict and control food quality. The purpose of this work is an overview of our findings concerning the hemisynthesis, the reactivity and the enzymatic oxidation of some flavonoids and shed light on the mechanisms involved in some of these processes and the structures of the resulting products. The free radical scavenging activity of some of the synthesized compounds is also presented and a structure-activity relationship is discussed. The first part of this review concerns the synthesis and structural characterization of modified monomeric flavanols. The use of these compounds as precursor for the preparation of natural and modified dimeric Molecules 2007, 12 2229 procyanidin derivatives was then explored through different coupling reactions. The full characterization of the synthesized compounds was achieved by concerted use of NMR and ESI-MS techniques. The free radical scavenging activity of some of the synthesized compounds was investigated. The second part of this review concerns the enzymatic oxidation of several flavonols by Trametes versicolor laccase. Most of the major oxidation products have been isolated as pure compounds and their structures unambiguously established through spectroscopic methods. Correlation between the structure of the oxidation product and the substitution pattern of the starting materials allows mechanistic features of this transformation to be elucidated.

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Synthesis of high molecular mass condensed tannin by cationic polymerization of flavan 3,4-carbonate

Cited by 26 publications

References 12 publications

Chemical Synthesis of Proanthocyanidins in Vitro and Their Reactions in Aging Wines

Chemical Synthesis of Proanthocyanidins in Vitro and Their Reactions in Aging Wines

Stereoselective Synthesis of Benzylated Prodelphinidins and Their Diastereomers with Use of the Mitsunobu Reaction in the Preparation of Their Gallocatechin Precursors

Flavonoids: Hemisynthesis, Reactivity, Characterization and Free Radical Scavenging Activity

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