Ellagitannin Chemistry. Preparative and Mechanistic Studies of the Biomimetic Oxidative Coupling of Galloyl Esters

Feldman, Ken S.; Ensel, Susan M.

doi:10.1021/ja00087a022

Cited by 73 publications

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“…For the exhaustive synthesis of ellagitannins, one of the most fundamental tasks is the formation of the chiral HHDP group, a C-C digallate, which has been achieved through several procedures [15][16][17][18] . The second and most impactful task would be the establishment of a methodology for synthesizing C-O digallates because their structure is the primary cause of structural diversity in this family.…”

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confidence: 99%

“…However, total synthesis via fully O-methylated ellagitannins might be unproductive because complete cleavage of methyl ethers without degradation of the other part of the molecule has been difficult. Feldman et al 15 stated that per-O-methyl ethers are not likely to be ultimately useful in natural product synthesis. Actually, no route has resulted in unprotected ellagitannins through the methyl (Me)-protection of phenols [25][26][27][28] .…”

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A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

et al. 2014

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Ellagitannins are a family of polyphenols containing more than 1,000 natural products. Nearly 40% of these compounds contain a highly oxygenated diaryl ether that is one of the most critical elements to their structural diversity. Here, we report a unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins. The strategy involves oxa-Michael addition of phenols to an orthoquinone building block, with subsequent elimination and reductive aromatization. The design of the building block-a halogenated orthoquinone monoketal of gallal-reduces the usual instability of orthoquinone and controls addition/elimination. Reductive aromatization is achieved with perfect chemoselectivity in the presence of other reducible functional groups. This strategy enables the synthesis of different diaryl ethers. The first total synthesis of a natural ellagitannin bearing a diaryl ethers is performed to demonstrate that the strategy increases the number of synthetically available ellagitannins.

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A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

et al. 2014

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“…Direct oxidative coupling of two unfunctionallized arenes to form biaryls and a phenanthrene ring would be much more attractive when taking the simplicity of manual work, availability of starting materials, and atom efficiency into consideration. Several direct oxidative coupling reagents have been developed, which include thalliumA C H T U N G T R E N N U N G (III) trifluoroacetate (TTFA), [5] 4 ], [6] vanadium oxytrifluoride (VOF 3 ) or vanadium oxytrichloride (VOCl 3 ), [7] hypervalent iodine, [8] and 2,3-dichloro-5,6-dicyanobenzoquinoneA C H T U N G T R E N N U N G (DDQ). [9] However, large excess amounts of oxidative reagents (at least stoichiometric equivalent), high toxicity, severe conditions, and/or low yields, also largely limit their applications.…”

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A Novel Sodium Nitrite‐Catalyzed Oxidative Coupling for Constructing Polymethoxyphenanthrene Rings

et al. 2012

Adv Synth Catal

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“…Feldman and co-workers used lead tetraacetate to generate the biaryl products 110a,b in a preparative study of the coupling reaction of methyl gallates 109a,b, respectively, for the synthesis of members of the ellagitannin family (Scheme 27) [78]. The outcome of this reaction is strongly influenced by the substitution pattern on the ring.…”

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Oxidative Aryl‐Coupling Reactions in Synthesis

Lessène

Feldman

2002

Modern Arene Chemistry

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The oxidant-mediated coupling of electron-rich arene rings has served over several decades as a valuable procedure to access biaryl units. The complex mixtures of isomers that often plagued the earliest studies have gradually given way to synthetically useful product distributions upon application of more selective coupling protocols. Continual advances in the nature of the oxidant (and its attendant ligands) and more precisely defined reaction conditions have led to increasing levels of control upon CaC bond formation. Chemoselective (CaC vs. CaO bond formation with phenols; suppression of product oxidation), regioselective (o-o 0 , vs. o-p 0 vs. p-p 0 CaC bond formation), and, more recently, stereoselective (atropisomer-selective) biaryl bond formation can now be achieved in many well-defined systems. A survey of the more recent advances in these areas is presented.14.1

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Ellagitannin Chemistry. Preparative and Mechanistic Studies of the Biomimetic Oxidative Coupling of Galloyl Esters

Cited by 73 publications

References 0 publications

A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

A unified strategy for the synthesis of highly oxygenated diaryl ethers featured in ellagitannins

A Novel Sodium Nitrite‐Catalyzed Oxidative Coupling for Constructing Polymethoxyphenanthrene Rings

Oxidative Aryl‐Coupling Reactions in Synthesis

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