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α-Pyrones with Diverse Hydroxy Substitutions from Three Marine-Derived Nocardiopsis Strains

Zhang, Haibo, Saurav, Kumar, Yu, Ziquan, Mándi, Attila, Kurtán, Tibor, Li, Jie, Tian, Xinpeng, Zhang, Qingbo, Zhang, Wenjun, Zhang, Changsheng
Journal of natural products 2016 v.79 no.6 pp. 1610-1618
Bacillus subtilis, Micrococcus luteus, Nocardiopsis, high performance liquid chromatography, isomers, spectral analysis
Eight new α-pyrones 1–8 and three known α-pyrones 9–11 were isolated from three marine-derived Nocardiopsis strains SCSIO 10419, SCSIO 04583, and SCSIO KS107. The structures of compounds 1–8 were elucidated by comprehensive spectral analyses. The absolute configurations of 4-deoxyphomapyrone C (1), 4-deoxy-11-hydroxyphomapyrone C (3), 4-deoxy-7R-hydroxyphomapyrone C (5), and phomapyrone C (11) were determined by TDDFT-ECD calculations for the solution conformers, which revealed that the conformation of the side chain was decisive for the sign of the characteristic high-wavelength ECD transition. (−)-4-Deoxy-8-hydroxyphomapyrone C (4) was isolated from SCSIO 10419 and was deduced as a diastereomeric mixture containing (8S)- and (8R)-4-deoxy-8-hydroxyphomapyrone C in a ratio of 2.6:1 (8R:8S), by chiral-phase HPLC analysis and Mosher’s ester analysis. Interestingly, 7-hydroxymucidone (9) was isolated from both SCSIO 04583 and SCSIO KS107, as an enantiomeric mixture containing (7S)-hydroxymucidone (major in 9 from SCSIO 04583) and (7R)-hydroxymucidone (major in 9 from SCSIO KS107). α-Pyrones 3–5 were identified as three isomers of phomapyrone C (11) with diverse hydroxy substitutions. α-Pyrones 10-hydroxymucidone (6), 4-hydroxymucidone (8), and 9, differed in the position of the hydroxy group. Several α-pyrones exhibited moderate growth inhibitory activity against Micrococcus luteus and Bacillus subtilis.