A MassQL-Integrated Molecular Networking Approach for the Discovery and Substructure Annotation of Bioactive Cyclic Peptides.

The marine sponge-derived fungus Stachylidium bicolor 293 K04 is a prolific producer of specialized metabolites, including certain cyclic tetrapeptides called endolides, which are characterized by the presence of the unusual amino acid N-methyl-3-(3-furyl)-alanine. This rare feature can be used as bait to detect new endolide-like analogs through customized fragment pattern searches of tandem mass spectrometry data using the Mass Spec Query Language (MassQL). Here, we integrate endolide-specific MassQL queries with molecular networking to obtain substructural information guiding the targeted isolation and structure elucidation of the new proline-containing endolides E (1) and F (2). We showed that endolide F (but not E) is a moderate antagonist of the arginine vasopressin V1A receptor, a member of the G protein-coupled receptor superfamily.

Planar pentacoordinate carbon in a 16-electron neutral CCu2Be3H4 cluster.

Planar hypercoordination in carbon is a fascinating area, which departs from the usual view of coordination geometry in carbon. Herein, we propose a planar pentacoordinate carbon species in the global minimum of the CCu2Be3H4 cluster. The cluster is a 16-electron species that is thermodynamically and kinetically very stable. Bonding analyses reveal 2π/6σ double aromaticity in the cluster. A low-energy isomerization pathway also reveals that the cluster has a sufficient lifetime for its experimental detection.

Rare Spin Avoided σ-σ Diradical Planar Tetracoordinate Boron Cluster: A Proto-Star for Planar Pentacoordination.

We report a global planar star-like cluster B3 Li3 featuring three planar tetracoordinate boron centres with a rare spin avoided σ-σ diradical character. The cluster was found to be stable towards dissociation into different fragments. The spin density was found to be localized solely on the three boron atoms in the molecular plane. This spin avoided σ-σ diradical character leads to the extension of the coordination number to yield a neutral B3 Li3 H3 and a cationic B3 Li3 H3 + cluster with three planar pentacoordinate boron centres in their global minimum structures. The planar geometry of the aninonic B3 Li3 H3 - cluster is slightly higher in energy. The planar global clusters were found to maintain planarity in their ligand protected benzene bound complexes, B3 Li3 (Bz)3 , B3 Li3 H3 (Bz)3 and B3 Li3 H3 (Bz)3 + with high ligand dissociation energies offering candidature for experimental detection.

Hetero-Polar Sextuple Bond: A Relativistic Quantum Chemical Study.

Number of bonds formed by sharing an electron pair between two atoms is not restricted to one, it can go beyond four and six is the maximum. While homopolar sextuple bond in Mo2 and W2 has been reported, such a high bond order in heteropolar diatomics has remained elusive. In the pursuit of the sextuple bond in polar diatomics, the present study depicts the existence of such multiple bonds in Rhodium-Scandium hetero-diatom based on relativistic quantum chemical calculations. The bonding comprises of three normal electron sharing covalent bonds and three dative covalent bonds.