Mixing hazard evaluation using small-scale Dewar vessels

Journal of Thermal Analysis and Calorimetry - In mixing hazard evaluations, a smaller scale is preferred for safety reasons and in order to conserve the samples. We have developed a small-scale...     

Protective effects of cyclodextrins on edaravone degradation induced by atmospheric oxygen or additive oxidant

Journal of Inclusion Phenomena and Macrocyclic Chemistry - Antioxidants scavenge free radicals and may help prevent disease. However, due to poor stability, continuous intake is required. This...     

Short synthesis of epi-cytoxazone via oxazoline formation through intramolecular benzylic substitution of a bis-trichloroacetimidate

A short and efficient method for synthesizing epi-cytoxazone via the corresponding oxazoline intermediate was developed. The formation of the oxazoline ring, which proceeds through an S_N1 mechanism to ensure that the trans-oxazoline stereochemistry is retained, was induced by intramolecular benzylic substitution of a 1,2-bis-trichloroacetimidate, starting from the known enantiomerically pure diol.     

Acylhydrazone Subunits as a Proton Cargo Delivery System in 7-Hydroxyquinoline

The reimagined concept of long-range tautomeric proton transfer using crane subunits is shown by designing and synthesising two new acylhydrazones containing a 7-hydroxyquinoline (7-OHQ) platform. The acylhydrazone subunits attached to the 7-OHQ at the 8th position act as crane arms for delivering proton cargo to the quinoline nitrogen. Light-induced tautomerization to their keto forms leads to Z/E isomerization of the C=C axle bond, followed by proton delivery to the quinoline nitrogen by the formation of covalent or hydrogen bonds. The axle‘s being either an imine or ketimine bond is the structural difference between the studied compounds. The −CH₃ group in the latter provides steric strain, resulting in different proton transport pathways. Both compounds show long thermal stability in the switched state, which creates a tuneable action of bidirectional proton cargo transport by using different wavelengths of irradiation. Upon the addition of acid, the quinoline nitrogen is protonated; this results in E/Z configuration switching of the acylhydrazone subunits. This was proven by single-crystal X-ray structure analysis and NMR spectroscopy.     

A matheuristic for the cell formation problem

In this paper we propose a GRASP matheuristic coupled with an Integer Programming refinement based on Set Partitioning to solve the Cell Formation Problem. We use the grouping efficacy measure to evaluate the solutions. As this measure is nonlinear, we propose a fractional Set Partitioning approach and its linearization. Our method is validated on a set of 35 instances from the literature. The experiments found four unknown solutions. For all instances with known optima, our method is able to determine the optimum solutions.     

DNA Damage Induced by Late Spring Sunlight in Antarctica

Sunlight ultraviolet (UV) radiation constitutes an important environmental genotoxic agent that organisms are exposed to, as it can damage DNA directly, generating pyrimidine dimers, and indirectly, generating oxidized bases and single-strand breaks (SSBs). These lesions can lead to mutations, triggering skin and eye disorders, including carcinogenesis and photoaging. Stratospheric ozone layer depletion, particularly in the Antarctic continent, predicts an uncertain scenario of UV incidence on the Earth in the next decades. This research evaluates the DNA damage caused by environmental exposure to late spring sunlight in the Antarctic Peninsula, where the ozone layer hole is more pronounced. These experiments were performed at the Brazilian Comandante Ferraz Antarctic Station, at King’s George Island, South Shetlands Islands. For comparison, tropical regions were also analyzed. Samples of plasmid DNA were exposed to sunlight. Cyclobutane pyrimidine dimers (CPDs), oxidized base damage and SSBs were detected using specific enzymes. In addition, an immunological approach was used to detect CPDs. The results reveal high levels of DNA damage induced by exposure under the Antarctic sunlight, inversely correlated with ozone layer thickness, confirming the high impact of ozone layer depletion on the DNA damaging action of sunlight in Antarctica.     

Chiral Benzazaborole-Catalyzed Regioselective Sulfonylation of Unprotected Carbohydrate Derivatives

Chiral benzazaborole-catalyzed regioselective sulfonylations of unprotected carbohydrate derivatives have been developed. This methodology enables direct regioselective functionalization of the secondary OH group in carbohydrate in the presence of the primary OH group. By using the chiral organoboron catalysis, kinetic resolution of the carbohydrate derivatives was also achieved.     

Polynomial combinatorial algorithms for skew-bisubmodular function minimization

Mathematical Programming - Huber et al. (SIAM J Comput 43:1064–1084, 2014) introduced a concept of skew bisubmodularity, as a generalization of bisubmodularity, in their complexity dichotomy...     

Diastereoselective synthesis of 5,5-disubstituted 3,3-difluorotetrahydrofurans

The diastereoselective synthesis of 5,5-disubstituted 3,3-difluorotetrahydrofurans 2 was achieved using β,β-difluorohomoallylic alcohols 1 as the key starting material in the presence of ICl (3.0?equiv) and tert-BuOK (1.5?equiv) in THF. The corresponding iodocyclization products 2 were obtained in good to moderate yields with excellent diastereo- and regioselectivities (d.r.?=?>20/1, 5-endo-trig only).