Aquiledine and cheliensisine are flavoalkaloids isolated from Aquilegia ecalcarata and Goniothalamus cheliensis, respectively. Different structures have been proposed for these
flavoalkaloids; however, their 1H and 13C NMR
spectroscopic data were virtually identical. In this study, the structures
of aquiledine and cheliensisine were revised on the basis of the DFT
calculation of NMR data including DP4+ and J-DP4
analysis, as well as specific rotations. Similarly, the structure
of isoaquiledine, a regioisomer of aquiledine, was also revised. A
biosynthetic pathway of these flavoalkaloids is proposed.
A cyclic epicatechin trimer with C3 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 (aR,aR,aR) configuration was formed atroposelectively in the cyclization process.
The Cover Feature shows the structure of a cyclic epicatechin trimer produced by oxidative coupling. The trimer has a C3 symmetric structure shaped like three cats sleeping. Its stereostructure was assigned on the basis of various spectroscopic data, including theoretical calculations of the NMR and ECD data. Epicatechin is a type of plant polyphenol and is present in various foods such as green tea, apples, grapes, and cocoa. During black tea production, various dimers and trimers of tea catechins, probably including the cyclic epicatechin trimer as well, are generated via enzymatic oxidation. More information can be found in the Communication by Y. Matsuo, T. Tanaka et al.
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