Cytochalasins from an Australian Marine Sediment-Derived Phomopsis sp. (CMB-M0042F): Acid-Mediated Intramolecular Cycloadditions Enhance Chemical Diversity

Chemical analysis of an Australian coastal marine sediment-derived fungus, Phomopsis sp. (CMB-M0042F), yielded the known cytochalasins J (<b>1</b>) and H (<b>2</b>), together with five new analogues, cytochalasins J₁–J₃ (<b>3</b>–<b>5</b>) and H₁ and H₂ (<b>6</b> and <b>7</b>). Structures of <b>1</b>–<b>7</b> were assigned on the basis of detailed spectroscopic analysis, chemical interconversion, and biosynthetic and mechanistic considerations. Of note, <b>1</b> and <b>2</b> proved to be highly sensitive to acid-mediated transformation, with <b>1</b> affording <b>3</b>–<b>5</b> and <b>2</b> affording <b>6</b> and <b>7</b>. Whereas <b>1</b>, <b>2</b>, <b>4</b>, and <b>5</b> were detected as natural products in crude culture extracts, <b>3</b>, <b>6</b>, and <b>7</b> were designated as acid-mediated handling artifacts. We propose novel stereo- and regiospecific intramolecular cycloadditions, under tight functional group control, that facilitate selective conversion of <b>1</b> and <b>2</b> to the rare 5/6/6/7/5- and 5/6/5/8-fused heterocycles <b>5</b> and <b>7</b>, respectively. Knowledge of acid sensitivity within the cytochalasin family provides a valuable cautionary lesson that has the potential to inform our analysis of past and future investigations into this structure class and inspire novel biomimetic transformations leading to new chemical diversity

Afurika nanbu ni okeru gengo no kiki - Matthias Brenzinger-shi ni kiku [Language Endangerment ion Southern Africa - Interview with Matthias Brenzinger]

Viridicatumtoxins, which belong to a rare class of fungal tetracycline-like mycotoxins, were subjected to comprehensive spectroscopic and chemical analysis, leading to reassignment/assignment of absolute configurations and characterization of a remarkably acid-stable antibiotic scaffold. Structure activity relationship studies revealed exceptional growth inhibitory activity against vancomycin-resistant Enterococci (IC₅₀ 40 nM), >270-fold more potent than the commercial antibiotic oxytetracycline

Waspergillamide A, a Nitro <i>depsi</i>-Tetrapeptide Diketopiperazine from an Australian Mud Dauber Wasp-Associated <i>Aspergillus</i> sp. (CMB-W031)

Chemical profiling of extracts from a mud dauber wasp-associated fungus, <i>Aspergillus</i> sp. (CMB-W031), revealed a remarkably diverse array of secondary metabolites, with many biosynthetic gene clusters being transcriptionally responsive to specific culture conditions. Chemical fractionation of a jasmine rice cultivation yielded many known fungal metabolites, including the highly cytotoxic (−)-stephacidin B and an unprecedented nonribosomal peptide synthase derived nitro <i>depsi</i>-tetrapeptide diketopiperazine, waspergillamide A (<b>1</b>). All structures were assigned by detailed spectroscopic analysis and, where appropriate, chemical degradation and Marfey’s analysis

Meroterpenoid and Diphenyl Ether Derivatives from <i>Penicillium</i> sp. MA-37, a Fungus Isolated from Marine Mangrove Rhizospheric Soil

<i>Penicillium</i> sp. MA-37, which was obtained from the rhizospheric soil of the mangrove plant <i>Bruguiera gymnorrhiza</i>, exhibited different chemical profiles in static and shaken fermentation modes. Three new meroterpenoid derivatives, 4,25-dehydrominiolutelide B (<b>1</b>), 4,25-dehydro-22-deoxyminiolutelide B (<b>2</b>), and isominiolutelide A (<b>3</b>), together with three known ones were characterized from its static fermentation, while three new diphenyl ether derivatives, namely, Δ^{1^′,3^′}-1′-dehydroxypenicillide (<b>4</b>), 7-<i>O</i>-acetylsecopenicillide C (<b>5</b>), and hydroxytenellic acid B (<b>6</b>), along with five related metabolites were isolated from the shaken culture. The structures of these compounds were elucidated on the basis of spectroscopic analysis, and the structure of compound <b>2</b> was confirmed by X-ray crystallographic analysis. The absolute configurations of <b>1</b>–<b>3</b> and <b>6</b> were determined by ECD and modified Mosher’s method, respectively. All isolated compounds were evaluated for brine shrimp lethality and antibacterial activity