Review for chiral-at-metal complexes and metal-organic framework enantiomorphs

This review discusses chiral-at-metal complexes and introduces enantiomorphs from assembly structure.Owing to the diverse coordination number and activity of metal ions as chiral centers, abundant structures for chiral selectivity, catalysis, and polarized light-response are the notable advantages of the chiral-at-metal complexes. The rational design and preparation of linear multi-dentate ligands is a good choice to improve the stability of chiral complexes, such as multi-bonding structure for high stability as a self-limiting system. The bio-significance and potential application of chiral-at-metal complexes are discussed, such as the synergistic effect of catalysis and chiral selectivity of the metal center in enzymes.Enzyme could be remolded to replace the original central metal ions with highly active rare earth or precious metal ions to form artificial metalloenzyme or to remove the ‘‘redundant" part around the metal center to improve the accessibility of substrate. The polarized light-response mechanism of chiral opsin is introduced in relation to its role in animal migration. Metal-organic frameworks(MOFs) are crystalline and porous materials built from metal nodes or clusters and organic linkers and provide the possibility to prepare artificial enantiomorphs. The preparations, applications, and characterization methods of MOF enatiomorphs are therefore introduced. We hope this review inspires researchers at all levels of their career to consider the title topic in their own research in terms of its application and potential value.

Highly Oxygenated Dimeric Grayanane Diterpenoids as Analgesics:TRPV1 and TRPA1 Dual Antagonists from Rhododendron molle

Six highly oxygenated dimeric grayanane diterpenoids(1—6)including three new ones,bismollethers A—C(1—3),were isolated from the flowers of Rhododendron molle collected at Qichun,Hubei,China.The structures and relative configurations of 1—6 were determined by comprehensive spectroscopic data analysis and 13C NMR calculation with DP4+analysis.The absolute configurations of bismollethers A—C(1—3)and birhodomollein B(5)were indubitably assigned by single-crystal X-ray diffraction analysis,revealing the head-to-tail linking manner of diterpenoid monomers.Bismollether A(1)is a caged dimeric grayanane diterpenoid linked through two oxygen-bridges of C-2−O−C-14′and C-14−O−C-2′,featuring a unique 1,8-dioxacyclotetradecane motif.The plausible biosynthesis pathways of 1—6 are proposed.All the isolates displayed significant analgesic activities and their structure-activity relationships were discussed.Grayanane diterpenoid dimers were found to be TRPV1 and TRPA1 dual antagonists,and docking studies provide a structural basis to design potent analgesics.