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Issue 9, 2019
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The absolute configurations of hyperilongenols A–C: rare 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinols with enolizable β,β′-tricarbonyl systems from Hypericum longistylum Oliv.

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Abstract

Three novel 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinol (PPAP) derivatives, named hyperilongenols A–C (1–3), were isolated from the stems and leaves of Hypericum longistylum Oliv. Their planar structures were established by a combination of 1D and 2D NMR, HRESIMS data, and chemical derivatization. Their absolute configurations were defined using electronic circular dichroism (ECD) spectroscopy and X-ray crystallography. Compounds 1–3 represent the first examples of naturally occurring 12,13-seco-spirocyclic PPAPs with an enolizable β,β′-tricarbonyl system. The O-methylation of compounds 1–3, coupled with comprehensive analyses of their X-ray diffraction data and variable-temperature 1H NMR spectra collected in different solvents, allowed us to propose a general mechanism underlying the formation of inseparable C-24 epimers of hyperilongenol A (1), decipher the solvent effects on the enolizable β,β′-tricarbonyl enol protons, and explore the possibilities of keto–enol interconversions of compounds 1–3. Moreover, a reasonable proposal for the structural determination of PPAPs with enolizable β-dicarbonyl and β,β′-tricarbonyl systems was developed. In addition, an in vitro bioassay showed that 2 exhibited potent antibacterial activity against Staphylococcus aureus.

Graphical abstract: The absolute configurations of hyperilongenols A–C: rare 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinols with enolizable β,β′-tricarbonyl systems from Hypericum longistylum Oliv.

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Publication details

The article was received on 15 Feb 2019, accepted on 18 Mar 2019 and first published on 20 Mar 2019


Article type: Research Article
DOI: 10.1039/C9QO00245F
Citation: Org. Chem. Front., 2019,6, 1491-1502

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    The absolute configurations of hyperilongenols A–C: rare 12,13-seco-spirocyclic polycyclic polyprenylated acylphloroglucinols with enolizable β,β′-tricarbonyl systems from Hypericum longistylum Oliv.

    N. Zhang, Z. Shi, Y. Guo, S. Xie, Y. Qiao, X. Li, Y. Xue, Z. Luo, H. Zhu, C. Chen, L. Hu and Y. Zhang, Org. Chem. Front., 2019, 6, 1491
    DOI: 10.1039/C9QO00245F

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