Diversification of a β-Lactam Pharmacophore via Allylic C-H Amination: Accelerating Effect of Lewis Acid Co-Catalyst

This report describes the use of Pd(II)/bis-sulfoxide 1 catalyzed intra- and intermolecular allylic C-H amination reactions to rapidly diversify structures containing a sensitive β-lactam core similar to that found in the monobactam antibiotic Aztreonam. Pharmacologically interesting oxazolidinone, oxazinanone, and linear amine motifs are rapidly installed with predictable and high selectivities under conditions that use limiting amounts of substrate. Additionally, we demonstrate for the first time that intramolecular C-H amination processes may be accelerated using catalytic amounts of a Lewis acid co-catalyst [Cr(III)(salen)Cl 2].     

Study of aggregation,denaturation and reduction of interferon alpha-2 products by size-exclusion high-performance liquid chromatography with fluorescence detection and biological assays

Interferon alpha-2 (IFN α-2) products have been widely used as antivirals for the treatment of serious diseases such as hepatitis B and C. However, reports of adverse reactions following treatment have prompted investigations into the cause of these undesirable events. In this study size-exclusion HPLC (SE-HPLC) methods coupled with intrinsic fluorescence detection were developed for evaluating the stability and degradation profiles of IFN α-2 drug substances and drug products. The method allowed baseline resolution of the active ingredient from the excipients present in the finished products that included large amounts of albumin. Limits of detection (S/N ≥ 3) for IFN α-2a and IFN α-2b were 32 ng/mL and 28 ng/mL, respectively and good repeatability of chromatographic profiles (%RSD < 2.1) was obtained. High molecular weight (HMW) aggregates with apparent molecular weight of ∼650 kDa as well as dimers, denatured and reduced variants were successfully identified and separated from native IFN α-2 proteins. This chromatographic method, which quantitatively measures physical and chemical changes taking place in solution formulations, was found to be capable of monitoring IFN α-2a and IFN α-2b stability. Potency assay results revealed up to 87% decrease in biological activity of the physically and chemically altered variants compared to the original IFNs.     

Surface pressure and flow field behind an oscillating fence submerged in turbulent boundary layer

Phase-locked PSP and PIV measurements were used to study the evolution of three-dimensional disturbances produced by an oscillating fence actuator immersed in a zero pressure gradient turbulent boundary layer. For the single fence frequency studied, strong three-dimensionality is observed in the vortical structure that varies along the span of the fence soon after the fence enters the flow. At the midspan, the structure grows, weakens, and convects faster than at other locations. As the fence height increases, the data indicate that the vortical structure terminates near the edge of the fence. In contrast, the vortex structure terminates on the plate surface adjacent to the fence edge as the fence descends, similar to a wake vortex of a stationary obstacle. This study demonstrates that the combined use of surface and flow-field diagnostics provide a link between flow field and surface features, yielding an understanding of the flow that would have not been possible with any one technique.     

New stable aryl-substituted acyclic imino-N-heterocyclic carbene: synthesis, characterisation and coordination to early transition metals

The synthesis of the bulky 1-(1-arylimino-2,2-dimethylpropyl)-3-(aryl)imidazolium salt from the corresponding imidazole and the activated imidoyl chloride is presented. The absence of acidic protons adjacent to the iminic carbon allowed for the first isolation of an imino-N-heterocyclic carbene of this ligand class. The free carbene was isolated, structurally characterised, and coordinated to titanium, zirconium, hafnium and chromium. The resulting metal halide complexes were fully characterised and were tested at room temperature and atmospheric pressure for their activity as ethylene polymerisation catalysts. The Zr(IV) complex was found to be the most active with a productivity of 140 kg PE mol M(-1) h(-1).     

Effects of Inoculum Physiological Stage on the Growth Characteristics of Chlorella sorokiniana Cultivated Under Different CO2 Concentrations

In order to maximize microalgae biomass production and reduce its overall costs, it is important to optimize inoculum conditions based on its physical and physiological characteristics. Chlorella sorokiniana cultures inoculated with inoculum at three different physiological stages (lag, exponential, and stationary) diluted to the same optical density were cultivated for 12?days under three different CO₂ concentrations (0.038, 5, or 10?% CO₂ v/v) and growth pattern and biomass production was observed. Samples inoculated with lag phase inoculum supplied with 5?% CO₂ achieved the maximum biomass production, whereas samples supplied with 0.038?% CO₂ never reached exponential growth. The better growth of samples inoculated with lag phase inoculum was attributed to its increased number of cells compared to the other two inocula.     

Alkyl 2,2,2-Trifluoroethanesulfonates (Tresylates): Elimination-Addition vs Bimolecular Nucleophilic Substitution in Reactions with Nucleophiles in Aqueous Media(1)

Alkyl 2,2,2-trifluoroethanesulfonate esters (tresylates), ROSO(2)CH(2)CF(3), react with aqueous base (pH >/= 9) to give the (alkoxysulfonyl)acetic acid, ROSO(2)CH(2)COOH; with the further addition of either a primary or secondary amine or of an alkanethiol, the product is the either the corresponding amide, ROSO(2)CH(2)C(O)NR(1)R(2), or a mixture in which the ketene dithioacetal, ROSO(2)CH=C(SR(1))(2), or the thioorthoester, ROSO(2)CH(2)C(SR(1))(3), may predominate. Kinetic and product studies are consistent with the following: (a) the reaction of tresylates with water is the normal sulfonic ester hydrolysis and (b) reaction with hydroxide is an (E1cB)(rev) process with loss of HF to yield the alkyl 2,2-difluoroethenesulfonate, ROSO(2)CH=CF(2), which rapidly yields the observed products. Benzyl 2,2,2-trifluoroethyl sulfone reacts analogously. The relationship between these observation with small molecules and those of earlier workers with tresyl agarose is discussed.