5.3. Experimental
5.3.6. Computational methods
The three dimensional structure of compound 5.5 was constructed using MOE 2013.0801. A conformational search by rotating the bond 8-8´ and the C7-OMe group with energy optimization was carried out with the Merck molecular force field (MMFF) (Halgren, 1996). Subsequently, all quantum mechanical calculations were performed with TURBOMOLE 6.5 using the graphical interface TmoleX. The force field minimum-energy structures were optimized with DFT-B3LYP (TZVPP) (Stephens et al., 1994). The CD spectra were calculated with the same method and basis set using Time-dependent density functional theory (TD-DFT) in TURBOMOLE. Visualization and comparison of the calculated spectra with the experimental one was performed with SpecDis Version 1.61 (Bruhn et al., 2013).
Appendix. Supporting Information (this is available online)
A supplemental data associated with this chapter can be found in the online and published part at http://www.sciencedirect.com/science/article/pii/S003194221400199X.
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Chapter 6
Prenylated phenyl polyketides and acylphloroglucinols from Hypericum peplidifolium
Graphical abstract*
Ten acetophenone derivatives including new pyranones and furans, along with known acylphloroglucinol type-compounds were isolated from the chemically unexplored Hypericum peplidifolium.
O O
OH
O
O O
unusual prenylated furan antifungal pyranone
OH O O
prenylated phenyl polyketide
Highlights
• First report on constituents and biological activity of Hypericum peplidifolium
• Detection of an unusual prenylated furan ring from the genus Hypericum
• Isolation, characterization, and bioactivity evaluation of phenyl polyketides and acylphloroglucinols
• Complete structural elucidation by HR-MS, 1D- and 2D-NMR
• Occurrence of rare methylated acylphloroglucinols
*This chapter (with slight modifications) was published: Fobofou, S.A.T., Harmon, C.R., Lonfouo, A.H., Franke, K., Wright, S.T., Wessjohann, A.L., 2016. Phytochemistry 124, 108-113. Reprinted (adapted) with permission from the Copyright Clearance Center (confirmation number: 11552515).
123 Abstract
In search for new or chemo-taxonomically relevant bioactive compounds from chemically unexplored Hypericum species, four previously undescribed natural products, named peplidiforones A-D were isolated and characterized from Hypericum peplidifolium A. Rich., together with six known compounds. The structures of all compounds were elucidated by extensive 1D- and 2D-NMR experiments, high resolution mass spectrometric analyses (HR-MS), and by comparison with data reported in the literature. Seven of these compounds are phenyl polyketides while three are acylphloroglucinol type compounds. Peplidiforone C, which possesses an unusual carbon skeleton consisting of a furan ring substituted by a 2,2-dimethylbut-3-enoyl moiety, is the first example of a prenylated furan derivative isolated from the genus Hypericum. The cytotoxicity, antifungal, and anti-herpes simplex virus type 1 (HSV-1) activities of extracts and compounds are described.
Keywords: Hypericum peplidifolium; Hypericaceae; polyketide derivatives; furans; pyranones;
prenylated natural products.
124