Synthesis of the [6–6–7–5–5] Pentacyclic Core of Calyciphylline N

A new approach for the concise 11-step synthesis of the [6–6–7–5–5] BCDEF pentacyclic core of calyciphylline N is described. A type II [5 + 2] cycloaddition was employed to construct the strained BCD skeleton, which encompasses the challenging bicyclo[2.2.2] and bicyclo[4.3.1] ring systems. With a regio- and diastereoselective Lu’s [3 + 2] cycloaddition, followed by intramolecular aldol cyclization and elimination, the desired [5–5]-fused EF ring system has been successfully installed, resulting in the complete carbocyclic skeleton of calyciphylline N

Dinuclear Aluminum Poly(phenolate) Complexes as Efficient Catalysts for Cyclic Carbonate Synthesis

A series of dinuclear aluminum complexes <b>1</b>–<b>4</b> stabilized by amine-bridged poly­(phenolato) ligands have been synthesized, which are highly active in catalyzing the cycloaddition of epoxides and CO₂. In the presence of 0.3 mol % complex <b>3</b> and 0.9 mol % NBu₄Br at 1 bar CO₂ pressure, terminal epoxides bearing different functional groups were converted to cyclic carbonates in 60–97% yields. Complex <b>3</b> is one of the rare examples of Al-based catalysts capable of promoting the cycloaddition at 1 bar pressure of CO₂. Moreover, reactions of more challenging disubstituted epoxides also proceeded at an elevated pressure of 10 bar and afforded cyclic carbonates in 52–90% yields

Dinuclear Aluminum Poly(phenolate) Complexes as Efficient Catalysts for Cyclic Carbonate Synthesis

A series of dinuclear aluminum complexes <b>1</b>–<b>4</b> stabilized by amine-bridged poly­(phenolato) ligands have been synthesized, which are highly active in catalyzing the cycloaddition of epoxides and CO₂. In the presence of 0.3 mol % complex <b>3</b> and 0.9 mol % NBu₄Br at 1 bar CO₂ pressure, terminal epoxides bearing different functional groups were converted to cyclic carbonates in 60–97% yields. Complex <b>3</b> is one of the rare examples of Al-based catalysts capable of promoting the cycloaddition at 1 bar pressure of CO₂. Moreover, reactions of more challenging disubstituted epoxides also proceeded at an elevated pressure of 10 bar and afforded cyclic carbonates in 52–90% yields

Kinetic Model of Nav1.5 Channel Provides a Subtle Insight into Slow Inactivation Associated Excitability in Cardiac Cells

<div><p>Voltage-gated sodium channel Nav1.5 has been linked to the cardiac cell excitability and a variety of arrhythmic syndromes including long QT, Brugada, and conduction abnormalities. Nav1.5 exhibits a slow inactivation, corresponding to a duration-dependent bi-exponential recovery, which is often associated with various arrhythmia syndromes. However, the gating mechanism of Nav1.5 and the physiological role of slow inactivation in cardiac cells remain elusive. Here a 12-state two-step inactivation Markov model was successfully developed to depict the gating kinetics of Nav1.5. This model can simulate the Nav1.5 channel in not only steady state processes, but also various transient processes. Compared with the simpler 8-state model, this 12-state model is well-behaved in simulating and explaining the processes of slow inactivation and slow recovery. This model provides a good framework for further studying the gating mechanism and physiological role of sodium channel in excitable cells.</p></div

Recyclable Single-Component Rare-Earth Metal Catalysts for Cycloaddition of CO₂ and Epoxides at Atmospheric Pressure

Ionic rare-earth metal complexes <b>1</b>–<b>4</b> bearing an imidazolium cation were synthesized, which, as single-component catalysts, showed good activity in catalyzing cyclic carbonate synthesis from epoxides and CO₂. In the presence of 0.2 mol % catalyst, monosubstituted epoxides bearing different functional groups were converted into cyclic carbonates in 60–97% yields under atmospheric pressure. In addition, bulky/internal epoxides with low reactivity yielded cyclic carbonates in 40–95% yields. More importantly, the readily available samarium complex <b>2</b> was reused for six successive cycles without any significant loss in its catalytic activity. This is the first recyclable rare-earth metal-based catalyst in cyclic carbonate synthesis

Production, Purification, and Antibiofilm Activity of a Novel Exopolysaccharide from <i>Arthrobacter</i> sp. B4

<div><p>A novel exopolysaccharide (EPS), namely, B4-EPS, is produced by <i>Arthrobacter</i> sp. B4. Response surface methodology (RSM) was employed to optimize the fermentation medium for increasing B4-EPS production. Based on Plackett–Burman design (PBD), glucose, yeast extract, and KH₂PO₄ were selected as significant variables, which were further optimized by a central composite design (CCD). According to response surface and canonical analysis, the optimal medium was composed of 16.94 g/L glucose, 2.33 g/L yeast extract, and 5.32 g/L KH₂PO₄. Under this condition, the maximum yield of B4-EPS reached about 8.54 g/L after 72 hr of batch fermentation, which was pretty close to the predicted value (8.52 g/L). Furthermore, B4-EPS was refined by column chromatography. The main homogeneous fraction (B4-EPS1) was collected and applied to assay of antibiofilm activity. B4-EPS1 exhibited a dose-dependent inhibitory effect on biofilm formation of <i>Pseudomonas aeruginosa</i> PAO1 without antibacterial activity. About 86.1% of biofilm formation of <i>P. aeruginosa</i> PAO1 was inhibited in the presence of 50 µg/mL B4-EPS1, which was more effective than the peer published data. Moreover, B4-EPS1 could prevent biofilm formation of other strains. These data suggest B4-EPS may represent a promising strategy to combat bacterial biofilms in the future.</p> </div