Stereospecific Nickel-Catalyzed Cross-Electrophile Coupling Reaction of Alkyl Mesylates and Allylic Difluorides to Access Enantioenriched Vinyl Fluoride-Substituted Cyclopropanes.

Cross-electrophile coupling reactions involving direct C-O bond activation of unactivated alkyl sulfonates or C-F bond activation of allylic gem-difluorides remain challenging. Herein, we report a nickel-catalyzed cross-electrophile coupling reaction between alkyl mesylates and allylic gem-difluorides to synthesize enantioenriched vinyl fluoride-substituted cyclopropane products. These complex products are interesting building blocks with applications in medicinal chemistry. Density functional theory (DFT) calculations demonstrate that there are two competing pathways for this reaction, both of which initiate by coordination of the electron-deficient olefin to the low-valent nickel catalyst. Subsequently, the reaction can proceed by oxidative addition of the C-F bond of the allylic gem-difluoride moiety or by directed polar oxidative addition of the alkyl mesylate C-O bond.

A Lewis Acid-Controlled Enantiodivergent Epoxidation of Aldehydes.

Two epoxidation catalysts, one of which consists of two VANOL ligands and an aluminum and the other that consists of two VANOL ligands and a boron, were compared. Both catalysts are highly effective in the catalytic asymmetric epoxidation of a variety of aromatic and aliphatic aldehydes with diazoacetamides, giving high yields and excellent asymmetric inductions. The aluminum catalyst is effective at 0 °C and the boron catalyst at -40 °C. Although both the aluminum and boron catalysts of (R)-VANOL give very high asymmetric inductions (up to 99% ee), they give opposite enantiomers of the epoxide. The mechanism, rate- and enantioselectivity-determining step, and origin of enantiodivergence are evaluated using density functional theory calculations.

Isotope Effects Reveal the Catalytic Mechanism of the Archetypical Suzuki-Miyaura Reaction.

Experimental and theoretical 13C kinetic isotope effects (KIEs) are utilized to obtain atomistic insight into the catalytic mechanism of the Pd(PPh3)4-catalyzed Suzuki-Miyaura reaction of aryl halides and aryl boronic acids. Under catalytic conditions, we establish that oxidative addition of aryl bromides occurs to a 12-electron monoligated palladium complex (Pd-(PPh3)). This is based on the congruence of the experimental KIE for the carbon attached to bromine (KIEC-Br = 1.020) and predicted KIEC-Br for the transition state for oxidative addition to the Pd(PPh3) complex (1.021). For aryl iodides, the near-unity KIEC-I of ~1.003 suggests that the first irreversible step in the catalytic cycle precedes oxidative addition and is likely the binding of the iodoarene to Pd(PPh3). Our results suggest that the commonly proposed oxidative addition to the 14-electron Pd(PPh3)2 complex can occur only in the presence of excess added ligand or under stoichiometric conditions; in both cases, experimental KIEC-Br of 1.031 is measured, which is identical to the predicted KIEC-Br for the transition state for oxidative addition to the Pd(PPh3)2 complex (1.031). The transmetalation step, under catalytic conditions, is shown to proceed via a tetracoordinate boronate (8B4) intermediate with a Pd-O-B linkage based on the agreement between an experimental KIE for the carbon atom involved in transmetalation (KIEC-Boron = 1.035) and a predicted KIEC-Boron for the 8B4 transmetalation transition state (1.034).

Annotated protein network analysis linking oral diseases.

Oral cancer is becoming more common, and it threatens to be a serious worldwide medical issue. Hence, it is of interest to elucidate the networks between proteins and biologically active compounds, as well as their functional annotations, and cell signaling pathways. The online STRING software was used to create a molecular genetics interaction network named AZURIN on oral bacterial proteins. We also used the cystoscope software to identify 11 nodes and 16 edges with an average node order of 2.91. Thus, we document data on the interaction of protein networks with other proteins for identifying potential therapeutic drug candidates linked to oral disease.

Metagenomic analysis of oral microbiota among oral cancer patients and tobacco chewers in Rajasthan, India.

Data on the microbial composition among tobacco chewers and oral cancer patients in Rajasthan, India is of interest. NGS analysis from tobacco chewers and oral cancer comprised the most abundant and core microbial taxa in the oral cavity. It shows that highly pathogenic phylum consisting of 6% Fusobacteria and 9% Firmicutes are observed in oral cancer samples; whereas, 0.6% Treponema, 34% Firmicutes, 0.02% Mollicutes, and 4% Fusobacteria are seen in tobacco chewers. Thus, data shows that the most abundant and core microbial taxa are found in the oral cavity of tobacco chewers and oral cancer patients in Rajasthan, India.

Statistical optimization for enhanced yields of probiotic Bacillus coagulans and its phage resistant mutants followed by kinetic modelling of the process.

Probiotics are microorganisms which when administered in adequate amounts confer health benefits to the host. A leading pharmaceutical company producing Bacillus coagulans as a probiotic was facing the problem of recurring phage attacks. Two mutants viz. B. co PIII and B. co MIII that were isolated as phage resistant mutants after UV irradiation and MMS treatment of phage sensitive B. coagulans parental culture were characterized at functional and molecular level and were noted to have undergone interesting genetic changes. The non-specific genetic alterations induced by mutagenesis can also lead to alterations in cell performance. Hence, in the current study the parental strain and the two mutants were selected for shake flask optimization. Plackett-Burman design was used to select the significant culture variables affecting biomass production. Evolutionary operation method was applied for further optimization. The study showed wide variations in the nutritional requirements of phage resistant mutants, post exposure to mutagens. An increment of 150, 134 and 152 % was observed in the biomass productions of B. coagulans (parental type) and mutants B.co PIII and B.co MIII respectively, compared to the yield from one-factor-at-a-time technique. Using Logistic and modified Leudeking-Piret equations, biomass accumulation and substrate utilization efficiency of the bioprocess were determined. The experimental data was in agreement with the results predicted by statistical analysis and modelling. The developed model may be useful for controlling the growth and substrate consumption kinetics in large scale fermentation using B. coagulans.

Nickel Decorated on Phosphorous-Doped Carbon Nitride as an Efficient Photocatalyst for Reduction of Nitrobenzenes.

Nickel nanoparticle-decorated phosphorous-doped graphitic carbon nitride (Ni@g-PC3N4) was synthesized and used as an efficient photoactive catalyst for the reduction of various nitrobenzenes under visible light irradiation. Hydrazine monohydrate was used as the source of protons and electrons for the intended reaction. The developed photocatalyst was found to be highly active and afforded excellent product yields under mild experimental conditions. In addition, the photocatalyst could easily be recovered and reused for several runs without any detectable leaching during the reaction.

A novel Ru/TiO2 hybrid nanocomposite catalyzed photoreduction of CO2 to methanol under visible light.

A novel in situ synthesized Ru(bpy)3/TiO2 hybrid nanocomposite is developed for the photoreduction of CO2 into methanol under visible light irradiation. The prepared composite was characterized by means of SEM, TEM, XRD, DT-TGA, XPS, UV-Vis and FT-IR techniques. The photocatalytic activity of the synthesized hybrid catalyst was tested for the photoreduction of CO2 under visible light using triethylamine as a sacrificial donor. The methanol yield for the Ru(bpy)3/TiO2 hybrid nanocomposite was found to be 1876 µmol g(-1) cat (ϕMeOH 0.024 mol Einstein(-1)) that was much higher in comparison with the in situ synthesized TiO2, 828 µmol g(-1) cat (ϕMeOH 0.010 mol Einstein(-1)) and the homogeneous Ru(bpy)3Cl2 complex, 385 µmol g(-1) cat (ϕMeOH 0.005 mol Einstein(-1)).

Intense white luminescence from combustion synthesized Ca12Al14O33:Yb(3+)/Yb(2+) single phase phosphor.

The Ca(12)Al(14)O(33):Yb(3+)/Yb(2+) single phase nano-phosphor has been synthesized through combustion route and its luminescence and lifetime studies have been carried out up to 20 K using 976 and 266 nm excitations. The samples heated in open atmosphere have shown the presence of Yb in Yb(3+) and Yb(2+) states. The 976 nm excitation results a cooperative upconversion emission at 486 nm due to the Yb(3+) state and a broad band in the blue region and has been assigned to arise from the defect centers. The 266 nm excitation on the other hand results a broad emission band even from as-synthesized phosphor without doping of Yb, the width of which increases in presence of Yb due to the emission from Yb(2+) ions formed in heated samples. The white emission covers almost whole visible region with bandwidth 190 nm. The ions in Yb(2+) state has been found to increase with the increase in heating temperature up to 1,273 K. A back conversion of Yb(2+) to Yb(3+) has been observed for higher temperatures. Effect of boric and phosphoric acids as flux on the emission properties of Yb(3+) and Yb(2+) states have been examined and discussed. Quantum yield of emission has also been determined for different samples.

Stimulation of dopamine D2 receptors in the nucleus accumbens inhibits inflammatory pain.

Previous studies suggest that dopamine in the nucleus accumbens links noxious or mesolimbic stimulation with the feedback inhibition of nociception. To test the hypothesis that pharmacological agonism at dopamine receptors in the nucleus accumbens elicits antinociception, we bilaterally microinjected dopamine D1- and D2-receptor subtype selective drugs, and then evaluated behavioral responses to noxious intraplantar formalin. While the D1-selective agonist SKF 38393 was without effect at a dose of 0.5 nmol/side, the D2-selective agonist quinpirole dose-dependently (0.05-5.0 nmol/side, bilateral) inhibited the persistent phase of formalin-induced nociception. This was blocked by pre-administration of a selective D2-dopaminergic antagonist raclopride (0.3 nmol/side, bilateral). Quinpirole did not produce overt behavioral effects and did not change rotarod latency. Our results indicate that quinpirole acts at dopamine D2 receptors in the nucleus accumbens to inhibit persistent nociception at doses that circumvent confounding non-specific motor deficits, namely, sedation and motor coordination.