In our continued search for biologically active metabolites from cultures of rare Basidiomycota species, we found eight previously undescribed cyathane-xylosides from submerged cultures of Dentipellis fragilis, which were named dentifragilins A–H. In addition, the known cyathane derivatives striatal D and laxitextine A were isolated. All compounds were characterized by high-resolution electrospray ionization mass spectrometry (HR-ESIMS) as well as by 1D and 2D nuclear magnetic resonance (NMR) spectroscopy. Several of the compounds exhibited significant activities in standardized cell-based assays for the determination of antimicrobial and cytotoxic effects. The discovery of cyathanes in the genus Dentipellis has chemotaxonomic implications, as this class of diterpenoids has already been shown to be characteristic for mycelial cultures of the related genera Hericium and Laxitextum, which are classified as Dentipellis in the family Hericiaceae.

Ophiofuranones A and B, metabolites of the fungus Ophiosphaerella korrae, were synthesized in 16 steps and 12%/22% yield. The stereogenic centers were established by Sharpless dihydroxylations and epoxidation, the 1,3-dienes via Wittig or HWE olefinations. The rings were closed through Knoevenagel-type condensation and lactonization. The ophiofuranones proved nontoxic at relevant concentrations against tumor cells, fibroblasts, and various bacteria and fungi. Ophiofuranone A and the monocyclic precursors 4 were weakly active against microbial biofilms.

In our ongoing search for new bioactive fungal metabolites, four previously undescribed oxazole carboxylic acid derivatives (1–4) for which we proposed the trivial names macrooxazoles A–D together with two known tetramic acids (5–6) were isolated from the plant pathogenic fungus Phoma macrostoma. Their structures were elucidated based on high-resolution mass spectrometry (HR-MS) and nuclear magnetic resonance (NMR) spectroscopy. The hitherto unclear structure of macrocidin Z (6) was also confirmed by its first total synthesis. The isolated compounds were evaluated for their antimicrobial activities against a panel of bacteria and fungi. Cytotoxic and anti-biofilm activities of the isolates are also reported herein. The new compound 3 exhibited weak-to-moderate antimicrobial activity as well as the known macrocidins 5 and 6. Only the mixture of compounds 2 and 4 (ratio 1:2) showed weak cytotoxic activity against the tested cancer cell lines with an IC50 of 23 µg/mL. Moreover, the new compounds 2 and 3, as well as the known compounds 5 and 6, interfered with the biofilm formation of Staphylococcus aureus, inhibiting 65%, 75%, 79%, and 76% of biofilm at 250 µg/mL, respectively. Compounds 5 and 6 also exhibited moderate activity against S. aureus preformed biofilm with the highest inhibition percentage of 75% and 73% at 250 µg/mL, respectively.

The fungal macrolide berkeleylactone A was synthesised in 13 steps and 24% yield using (R)-propylene oxide and an asymmetric Noyori hydrogenation of a β-ketoester to instal the stereogenic centres. A...