Abstract
In a study of the antifungal activity of selected compounds as potentials agrochemicals, we have prepared and characterized by elemental analyses, infrared and NMR spectroscopies three new bis-gamma-lactones analogous to avenaciolide, where the octyl group of this natural product was replaced by heptyl, hexyl and pentyl groups. The effects on the mycelia development and conidia germination of Colletotrichum gloesporioides of these compounds and their synthetic precursors were evaluated in vitro. The title compounds were active in the tested conditions, while all the synthetic precursors were inactive. The preparation and characterization of 15 new synthetic intermediates are also described.
Highlights
Avenaciolide (Figure 1) is a natural product isolated from Aspergillus avenaceus, which possesses several interesting biological activities such as antifungal, antibacterial activities and inhibition of the glutamate transport in mitochondria.[1,2,3,4,5,6,7]
Isoavenaciolide, a related natural bis-γ-lactone which differs from avenaciolide by the orientation of the side chain (Figure 1), is about five times less effective than avenaciolide as an inhibitor of the glutamate transport while the analogue ethisolide is inactive.[2,8]
A review on the synthesis of avenaciolide and related metabolites has been published by Martin et al.[9]
Summary
Avenaciolide (Figure 1) is a natural product isolated from Aspergillus avenaceus, which possesses several interesting biological activities such as antifungal, antibacterial activities and inhibition of the glutamate transport in mitochondria.[1,2,3,4,5,6,7] Isoavenaciolide, a related natural bis-γ-lactone which differs from avenaciolide by the orientation of the side chain (Figure 1), is about five times less effective than avenaciolide as an inhibitor of the glutamate transport while the analogue ethisolide is inactive.[2,8] These findings suggest the crucial role played by the configuration of the C-6 stereogenic center and the length of the hydrophobic alkyl side chain on the biological activities.A review on the synthesis of avenaciolide and related metabolites has been published by Martin et al.[9]. The coupling constant of 10.9 Hz observed in the 1H NMR spectra of these compounds for the olefinic hydrogens 1” and 2” confirmed the formation of the expected Z isomers. The hydrogenation of 3 (a, b, c) yielded the compounds 4 (a, b, c) which 13C NMR spectra showed the two methylene signals at ca.
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