Highly Enantioselective Catalysis by Enzyme Encapsulated in Metal Azolate Frameworks with Micelle-Controlled Pore Sizes.

Encapsulating enzymes within metal-organic frameworks has enhanced their structural stability and interface tunability for catalysis. However, the small apertures of the frameworks restrict their effectiveness to small organic molecules. Herein, we present a green strategy directed by visible linker micelles for the aqueous synthesis of MAF-6 that enables enzymes for the catalytic asymmetric synthesis of chiral molecules. Due to the large pore aperture (7.6 Å), double the aperture size of benchmark ZIF-8 (3.4 Å), MAF-6 allows encapsulated enzyme BCL to access larger substrates and do so faster. Through the optimization of surfactants' effect during synthesis, BCL@MAF-6-SDS (SDS = sodium dodecyl sulfate) displayed a catalytic efficiency (Kcat/Km) that was 420 times greater than that of BCL@ZIF-8. This biocomposite efficiently catalyzed the synthesis of drug precursor molecules with 94-99% enantioselectivity and nearly quantitative yields. These findings represent a deeper understanding of de novo synthetic encapsulation of enzyme in MOFs, thereby unfolding the great potential of enzyme@MAF catalysts for asymmetric synthesis of organics and pharmaceuticals.

Reversible Stereoisomerization of 1,3-Diphosphetane Frameworks Revealed by a Single-Electron Redox Approach.

The discovery of pyramidal inversion has continued to impact modern organic and organometallic chemistry. Sequential alkylation reactions of an N-heterocyclic carbene (NHC) ligated dicarbondiphosphide 1 with RI (R = Me, Et, or iBu) and ZnMe2 give rise to the highly stereoselective synthesis of cis-1,3-diphosphetanes 3. cis-3 is conformationally favorable at room temperature, whereas inversion to trans-3 is observed at 110 °C. One-electron oxidation of cis-3 with Fc+(BArF) (Fc = [Fe(C5H5)2]; BArF = [B(3,5-(CF3)2C6H3)4)]-) leads to the stereoselective formation of trans-1,3-diphosphetane radical cation salts 3•+(BArF), which can be reversibly transformed to cis-3 upon one-electron reduction. Salts 3•+(BArF) represent the first examples of 1,3-diphosphetane radical cations. These results provide a potential application of planar four-membered heterocycle-based building blocks for electrically fueled molecular switches.

Statistical research on the bioactivity of new marine natural products discovered during the 28 years from 1985 to 2012.

Every year, hundreds of new compounds are discovered from the metabolites of marine organisms. Finding new and useful compounds is one of the crucial drivers for this field of research. Here we describe the statistics of bioactive compounds discovered from marine organisms from 1985 to 2012. This work is based on our database, which contains information on more than 15,000 chemical substances including 4196 bioactive marine natural products. We performed a comprehensive statistical analysis to understand the characteristics of the novel bioactive compounds and detail temporal trends, chemical structures, species distribution, and research progress. We hope this meta-analysis will provide useful information for research into the bioactivity of marine natural products and drug development.

Loddigesiinols G-J: α-glucosidase inhibitors from Dendrobium loddigesii.

Four new polyphenols, loddigesiinols G-J (compounds 1-4) and a known compound, crepidatuol B (5), were isolated from the stems of Dendrobium loddigesii that have long been used in Traditional Chinese Medicine and have recently been used to treat type 2 diabetes. Compounds 1-5 structures were elucidated based on spectroscopic analysis. The absolute configurations of compounds 1-4 were determined using theoretical calculations of electronic circular dichroism (ECD), and the absolute configuration of compound 5 was determined by a comparison of the experimental ECD spectra and the literature data. Compounds 1-5 are strong inhibitors of α-glucosidase, with IC50 values of 16.7, 10.9, 2.7, 3.2, and 18.9 µM, respectively. Their activities were significantly stronger than trans-resveratrol as a positive control (IC50 values of 27.9 µM).

Statistical research on marine natural products based on data obtained between 1985 and 2008.

Since the 1960s, more than 20,000 compounds were discovered from marine organisms. In this paper we performed a quantitative analysis for the novel marine natural products reported between 1985 and 2008. The data was extracted mainly from the reviews of Faulkner and Blunt [1-26]. The organisms producing these marine natural products are divided into three major biological classes: marine microorganisms (including phytoplankton), marine algae and marine invertebrate. The marine natural products are divided into seven classes based on their chemical structure: terpenoids, steroids (including steroidal saponins), alkaloids, ethers (including ketals), phenols (including quinones), strigolactones, and peptides. The distribution and the temporal trend of these classes (biological classes and chemical structure classes) were investigated. We hope this article provides a comprehensive perspective on the research of marine natural products.