Bioinspired Total Synthesis of (−)‐Vescalin: A Nonahydroxytriphenoylated <i>C</i>‐Glucosidic Ellagitannin

Hexahydroxydiphenoyl (HHDP) and dehydrohexahydroxydiphenoyl (DHHDP) groups are the major acyl components of ellagitannins, which are polyphenols whose biosynthesis have attracted considerable attention; however, the mechanisms of the production of HHDP and DHHDP in the ellagitannin biosynthesis have not been clarified. With the aim of elucidating such a mechanism, this study investigates the CuCl2‐mediated oxidation of simple galloyl derivatives in an aqueous medium. It is shown that the oxidation of methyl gallate affords a DHHDP‐type dimer, whose reduction with Na2S2O4 yields an HHDP‐type dimer. However, the oxidation of the HHDP‐type product over CuCl2 does not afford the parent DHHDP ester. The oxidation of 1,4‐butanediol digallate under the same conditions produces a DHHDP‐type product via the intramolecular coupling of galloyl groups. These results strongly suggest that the DHHDP group is the initial product of the oxidative coupling of two galloyl groups in the ellagitannin biosynthesis, and subsequent reductive metabolism affords HHDP esters.

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Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

Yamashita

Matsuo

Saito

et al. 2021

Chemistry An Asian Journal

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A CommonC₂‐Symmetric 2,2’‐Biphenol Building Block and its Application in the Synthesis of (+)‐di‐epi‐Gonytolide A

Greb

Drennhaus

Klischan

et al. 2023

Chemistry A European J

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A variety of biaryl polyketides exhibit remarkable bioactivities. However, their synthetic accessibility is often challenging. Herein, the enantioselective preparation and synthetic application of an axially chiral 2,2'-biphenol building block is outlined that represents a common motif of these intriguing natural products. Based on the highly regioselective and scalable bromination of a phenol precursor, a coupling process by Lipshutz cuprate oxidation was developed. A copper-mediated deracemization strategy proved to be superior to derivatization or kinetic resolution approaches. Key steps in the overall building block synthesis were rationalized through DFT studies. Utilizing the 2,2'-biphenol, a highly diastereoselective five step synthesis of formerly unknown (+)-di-epi-gonytolide A was developed, thus showcasing the building block's general potential for the synthesis of natural products and their derivatives. En route, the first enantioselective construction of a chromone dimer intermediate was established.

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Bioinspired Total Synthesis of (−)‐Vescalin: A Nonahydroxytriphenoylated C‐Glucosidic Ellagitannin

Cited by 2 publications

References 59 publications

Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

A CommonC₂‐Symmetric 2,2’‐Biphenol Building Block and its Application in the Synthesis of (+)‐di‐epi‐Gonytolide A

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Bioinspired Total Synthesis of (−)‐Vescalin: A Nonahydroxytriphenoylated C‐Glucosidic Ellagitannin

Cited by 2 publications

References 59 publications

Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

Formation of Dehydrohexahydroxydiphenoyl Esters by Oxidative Coupling of Galloyl Esters in an Aqueous Medium Involved in Ellagitannin Biosynthesis

A CommonC2‐Symmetric 2,2’‐Biphenol Building Block and its Application in the Synthesis of (+)‐di‐epi‐Gonytolide A

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A CommonC₂‐Symmetric 2,2’‐Biphenol Building Block and its Application in the Synthesis of (+)‐di‐epi‐Gonytolide A