Conformational Analysis of an Antibacterial Cyclodepsipeptide Active against Mycobacterium tuberculosis by a Combined ROE and RDC Analysis.

Griselimycin (GM) and methylgriselimycin (MGM), naturally produced by microorganisms of the genus Streptomyces, are cyclic depsipeptides composed of ten amino acids. They exhibit antibacterial activity against Mycobacterium species by inhibiting the sliding clamp of prokaryotic DNA polymerase III and are therefore considered as potential anti-tuberculosis drugs. The difference between the peptides is the presence of l-(R)-4-methyl-proline in MGM instead of l-proline in GM at position 8 of the amino acid sequence.

Uncovering Key Structural Features of an Enantioselective Peptide-Catalyzed Acylation Utilizing Advanced NMR Techniques.

We report on a detailed NMR spectroscopic study of the catalyst-substrate interaction of a highly enantioselective oligopeptide catalyst that is used for the kinetic resolution of trans-cycloalkane-1,2-diols via monoacylation. The extraordinary selectivity has been rationalized by molecular dynamics as well as density functional theory (DFT) computations. Herein we describe the conformational analysis of the organocatalyst studied by a combination of nuclear Overhauser effect (NOE) and residual dipolar coupling (RDC)-based methods that resulted in an ensemble of four final conformers.

Exploring the conformational space of bridge-substituted dithienylcyclopentenes.

Stimuli responsive compounds and materials are of high interest in synthetic chemistry and materials science, with light being the most intriguing stimulus due to the possibility to remote control the physicochemical properties of a molecule or a material. There is a constant quest to design photoswitches with improved switching efficiency and especially diarylethene-type switches promise photo cyclization quantum yields up to unity. However, only limited attention has been paid towards the influence of the solution conformation on the switching efficiency.

RDC-based determination of the relative configuration of the fungicidal cyclopentenone 4,6-diacetylhygrophorone A12.

The hygrophorones, a class of cyclopentenones isolated from fruiting bodies of the genus Hygrophorus (basidiomycetes), show promising antifungal activity. While the constitution of 4,6-diacetylhygrophorone A(12) (3) and the relative configuration of the stereogenic centers in the cyclopentenone ring were elucidated using standard NMR and MS techniques, the relative configuration of the exocyclic stereogenic center could not be assigned. By introducing a sample of 3 into an alignment medium and measuring anisotropic NMR parameters, namely, residual dipolar couplings, we were able to unambiguously determine the relative configuration of all three stereogenic centers in 4,6-diacetylhygrophorone A(12) simultaneously by fitting several structure proposals to the experimental data.