Regarding targeted disruption of epigenetic regulators, histone methyltransferase and deacetylase in a plant endophytic fungus Pestalotiopsis fici have been uncovered as an unexplored chemical repertoire. Manipulation of epigenetic regulators led to the isolation of 15 new polyketides, including pestaloficiols T-W (1-3 and 5), as well as 11 macrodiolide ficiolides A-K (6-16). Ficiolide K (16) was found to contain a very rare 1,6-anhydro-pyranose moiety. Finally, the biosynthetic origin of macrodiolide was characterized by isotope-labeling experiments.
Six unusual xanthone-chromanone dimers, versixanthones A-F (1-6), featuring different formal linkages of tetrahydroxanthone and 2,2-disubstituted chroman-4-one monomers, were isolated from a culture of the mangrove-derived fungus Aspergillus versicolor HDN1009. The absolute configurations of 1-6, representing the central and axial chirality elements or preferred helicities, were established by a combination of X-ray diffraction analysis, chemical conversions, and TDDFT-ECD calculations. The interconversion of different biaryl linkages between 1 and 4 and between 2 and 3 in DMSO by a retro-oxa-Michael mechanism provided insight into the formation of the xanthone-chromanone dimers and supported the assignments of their absolute configurations. Compounds 1-6 exhibited cytotoxicities against the seven tested cancer cell lines, with the best IC50 value of 0.7 μM. Compound 5 showed further inhibitory activity against topoisomerase I.
Five new fungal hybrid polyketides, cladosins A-D (1-4), that contain a novel linear 6(3)-enamino-8,10-dihydroxy-tetraketide (1 and 2) or 6-enamino-7(8)-en-10-ol (3 and 4) moiety, as well as the biogenetically related cladosin E (5), were isolated from the deep-sea-derived fungus Cladosporium sphaerospermum 2005-01-E3. Their structures (1-5) were elucidated through a combination of spectroscopic data, chemical conversion, and both Mosher's and Marfey's methods for stereochemical assignment. A plausible biogenetic pathway to 1-5 is proposed. Cladosin C (3) possesses mild anti-influenza A H1N1 virus activity.
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