359. Gallotannins. Part II. Some esters and depsides of gallic acid

Haslam, Edwin; Haworth, Robert D.; Mills, S. D.; Rogers, H. J.; Armitage, R.; Searle, T.

doi:10.1039/jr9610001836

Cited by 40 publications

(26 citation statements)

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“…75 observed that galloyl~gallate side-chains in polygalloylquinic acid tannins were very susceptible to methanolysis in the range pH 4~6. Ethanol had less effect, butanol had none.…”

Section: Alcoholysismentioning

confidence: 98%

Chlorogenic Acids

Clifford¹

1985

Coffee

119

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“…75 observed that galloyl~gallate side-chains in polygalloylquinic acid tannins were very susceptible to methanolysis in the range pH 4~6. Ethanol had less effect, butanol had none.…”

Section: Alcoholysismentioning

confidence: 98%

Chlorogenic Acids

Clifford¹

1985

Coffee

119

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“…These gallotannins contain a ß-penta-O-galloylglucose nucleus, to which some three or four additional galloyl groups are attached by depsidic linkages (e.d. Haslam et al 1961). The remaining constituents are mixtures of gallic acid (21%), m-digallic acid (7%), pentagalloylglucose (3%) and an undefined fraction suggested to be a trigallic acid (1%) (Jurd 1962).…”

Section: Moisture Contentmentioning

confidence: 99%

Acidity of Heartwood and Sapwood in Some Eucalypt Species

Krilov¹,

Lasander²

1988

Holzforschung

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“…[12]. By filtration, removal of the solvent and washing with acetone (to remove diphenylmethane), 3a-H 4 is …”

Section: Resultsmentioning

confidence: 99%

Linear oxygen-donor ligands derived from gallic acid methyl ester: ligand synthesis and preliminary coordination studies

Albrecht¹,

Schneider

1999

J. prakt. Chem.

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657Helicates as well as meso-helicates are intensive studied metallo-supramolecular targets. On the one hand it is of interest to investigate into the structure and the self-assembly of the oligonuclear supramolecular coordination compounds [1 -3]. On the other hand the use of helicates for the preparation of materials with special physical properties [4] or of topologically interesting molecules [5] has to be investigated. For the latter linear organic donor molecules have to be designed and synthesized which bear reactive functional groups to enable further derivatization of the ligands or of the selfassembled metal complexes.Many investigations towards the formation and properties of helicate-type structures were performed with oligo-nitrogen-donor ligands [2]. Corresponding oxygen-donors were investigated to a minor extend [3]. Hereby mainly oligo-catechol units that were connected by different types of spacers were used as the metal coordination sites [6 -10].Abstract. The new ligands 3a-c-H 4 with two catechol-type oxygen-donor binding sites and ether-linked spacers are synthesized in three step procedures starting from gallic acid methyl ester 4. After protection of two OH-functions as benzophenone ketale, a Williamson ether synthesis introduces the spacer, and finally the ketale is removed again. Prelimiand aryl bridges are connected directly to the coordinating units [10]. In this paper we present a simple approach to a novel type of dicatechol ligands 3a-c-H 4 which possess ether bridges in the spacer and ester groups as substituents at the aromatic units. Additionally, we describe preliminary coordination studies with titanium(IV) ions in the presence of alkali metal cations or ammonium cations. Results and DiscussionThe synthesis of the ligands 3a-c-H 4 is achieved in a three step procedure starting from gallic acid methyl ester 4. Initially two out of the three hydroxy groups of the ester 4 are protected by formation of the benzophenone ketal 5. As described by Jurd [11], heating of gallic acid methyl ester 4 in the presence of an equimolar amount of dichlorodiphenylmethane for 5 min to 175 °C affords compound 5 as a white solid in 91% yield (Scheme 1).Reaction of the ketal 5 (2 eq.) with 1,3-diiodopropane, 1,4-diiodobutane, or 1,6-diiodohexane (1 eq.) in acetone in the presence of potassium carbonate at reflux leads overnight in a Williamson ether synthesis to the ligand precursors 6a (61% yield), 6b (80% yield) and 6c (71% yield). In the final step the ketal moieties are cleaved by heating of 6a -c in acetic acid. The acetic acid is evaporated in vacuo, and the benzophenone is removed by extraction with ether and n-hexane. The ligands 3a/b-H 4 are both obtained in 86% yield and 3c-H 4 in 97% yield as white solids.As an alternative, the ketal 6a also can be transformed into the ligand 3a-H 4 by stirring a mixture of 6a and of palladium on charcoal in dichloromethane for 15 h under an atmosphere of 55 bar of hydrogen (autoclave!) [12]. By filtration, removal of the solvent and washing with acetone (...

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359. Gallotannins. Part II. Some esters and depsides of gallic acid

Cited by 40 publications

References 0 publications

Chlorogenic Acids

Chlorogenic Acids

Acidity of Heartwood and Sapwood in Some Eucalypt Species

Linear oxygen-donor ligands derived from gallic acid methyl ester: ligand synthesis and preliminary coordination studies

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