The Disorazole Z Family of Highly Potent Anticancer Natural Products from Sorangium cellulosum: Structure, Bioactivity, Biosynthesis, and Heterologous Expression.

Myxobacteria serve as a treasure trove of secondary metabolites. During our ongoing search for bioactive natural products, a novel subclass of disorazoles termed disorazole Z was discovered. Ten disorazole Z family members were purified from a large-scale fermentation of the myxobacterium Sorangium cellulosum So ce1875 and characterized by electrospray ionization-high-resolution mass spectrometry (ESI-HRMS), X-ray, nuclear magnetic resonance (NMR), and Mosher ester analysis.

Control of stress and damage in structures by piezoelectric actuation: 1D theory and monofrequent experimental validation.

This contribution presents novel results on feed-forward control of stress in piezoelectric structures by means of piezoelectric actuation. For that sake, we focus on a one-dimensional benchmark problem, a piezoelectric transducer that is excited by a piezoelectric stack actuator. We investigate the following problem: Is it possible to actuate the piezoelectric transducer in such a manner that the dominant axial stress component is nullified.

A fluorescence anisotropy assay to discover and characterize ligands targeting the maytansine site of tubulin.

Microtubule-targeting agents (MTAs) like taxol and vinblastine are among the most successful chemotherapeutic drugs against cancer. Here, we describe a fluorescence anisotropy-based assay that specifically probes for ligands targeting the recently discovered maytansine site of tubulin. Using this assay, we have determined the dissociation constants of known maytansine site ligands, including the pharmacologically active degradation product of the clinical antibody-drug conjugate trastuzumab emtansine.

Solving the Puzzle of One-Carbon Loss in Ripostatin Biosynthesis.

Ripostatin is a promising antibiotic that inhibits RNA polymerase by binding to a novel binding site. In this study, the characterization of the biosynthetic gene cluster of ripostatin, which is a peculiar polyketide synthase (PKS) hybrid cluster encoding cis- and trans-acyltransferase PKS genes, is reported. Moreover, an unprecedented mechanism for phenyl acetic acid formation and loading as a starter unit was discovered.

Stereochemical determination of the leupyrrins and total synthesis of leupyrrin A1.

The stereochemical determination of the potent antifungal agents leupyrrin A1 and B1 and the total synthesis of leupyrrin A1 are reported. The relative and absolute configuration was determined by a combination of high field NMR studies, molecular modeling, and chemical derivatization. The expedient total synthesis involves a one-pot sequential Zr-mediated oxidative diyne-cyclization/regioselective opening sequence for preparation of the unique dihydrofuran ring, a highly stereoselective one-pot approach to the butyrolactone, a challenging sp(2)-sp(3) Suzuki coupling and a high-yielding Shiina macrolactonization.