Stereochemistry of a Cyclic Epicatechin Trimer with C3 Symmetry Produced by Oxidative Coupling. Issue 5 (5th January 2021)

• Record Type: Journal Article
• Authors: Kawazoe, Rina; Matsuo, Yosuke; Saito, Yoshinori; Tanaka, Takashi
• Is Part Of: European journal of organic chemistry. Issue 5(2021)
• Page Start: 777
• Page End: 781
• Publication Date: 2021-01-05
• Subjects: Atropisomerism -- Density functional calculations -- Macrocycles -- Natural Products -- Oxidation; Chemistry, Organic -- Periodicals; Organic compounds -- Synthesis -- Periodicals; Bioorganic chemistry -- Periodicals; Chemistry, Physical organic -- Periodicals; 547
• DOI: 10.1002/ejoc.202001579
• Languages: English
• ISSNs: 1434-193X

Abstract

Abstract: A cyclic epicatechin trimer with C 3 symmetry, connected through C−C bonds between A‐ and B‐rings, was isolated as an oxidative coupling product of (−)‐epicatechin with polyphenol oxidase. It was previously isolated as an oxidation product of epicatechin with CuCl2 ; however, only the 2D structure was proposed. Its stereochemistry was assigned using various spectroscopic techniques, including 1D and 2D NMR, and theoretical calculations of the NMR and ECD data. It was suggested that the less strained cyclic trimer with the (a R, a R, a R ) configuration was formed atroposelectively in the cyclization process. Abstract : A cyclic epicatechin trimer with C 3 symmetry, connected through C−C bonds between A‐ and B‐rings, was isolated as an oxidative coupling product of (−)‐epicatechin in the presence of polyphenol oxidase. Its stereochemistry was assigned using 1D and 2D NMR, and theoretical calculations of the NMR and ECD data. We suggest that the less strained cyclic trimer with the (a R, a R, a R ) configuration was formed atroposelectively in the cyclization process.