A highly enantioselective one-pot synthesis of homoallylic alcohols via tandem asymmetric allyl transfer/olefin cross metathesis

A highly enantioselective one-pot synthesis of linear homoallylic alcohols with terminal ester functionality has been achieved. The reactions were controlled by ordered addition of reagents and catalysts, ensuring complete consumption of aldehyde. The synthetic utility of this strategy has been demonstrated in a short synthesis of a low boiling point intermediate for grahamimycin A.     

BrdU-positive cells in the neonatal mouse hippocampus following hypoxic-ischemic brain injury

Background  

Mechanisms that affect recovery from fetal and neonatal hypoxic-ischemic (H-I) brain injury have not been fully elucidated. The incidence of intrapartum asphyxia is approximately 2.5%, but the occurrence of adverse clinical outcome is much lower. One of the factors which may account for this relatively good outcome is the process of neurogenesis, which has been described in adult animals. We used a neonatal mouse model to assess new cells in the hippocampus after H-I injury.     

An unusual approach to the synthesis of enantiomerically cis linear homoallylic alcohols based on the steric interaction mechanism of camphor scaffold

Camphor is used as the chiral auxiliary for the enantioselective synthesis of cis linear homoallylic alcohols. A range of catalysts, aldehydes, and solvents were investigated to obtain the optimum yield, enantioselectivity, and cis olefinic geometry. [structure: see text]     

Structure-based design of Aurora A & B inhibitors

The Aurora family of serine/threonine kinases are mitotic regulators involved in centrosome duplication, formation of the bipolar mitotic spindle and the alignment of the chromosomes along the spindle. These proteins are frequently overexpressed in tumor cells as compared to normal cells and are therefore potential therapeutic oncology targets. An Aurora A high throughput screen revealed a promising sub-micromolar indazole-benzimidazole lead. Modification of the benzimidazole portion of the lead to a C2 linker with a phenyl ring was proposed to achieve novelty. Docking revealed that a conjugated linker was optimal and the resulting compounds were equipotent with the lead. Further structure-guided optimization of substituents on the 5 & 6 position of the indazole led to single digit nanomolar potency. The homology between the Aurora A & Aurora B kinase domains is 71% but their binding sites only differ at residues 212 & 217 (Aurora A numbering). However interactions with only the latter residue may be used for obtaining selectivity. An analysis of published Aurora A and Aurora B X-ray structures reveals subtle differences in the shape of the binding sites. This was exploited by introduction of appropriately sized substituents in the 4 & 6 position of the indazole leading to Aurora B selective inhibitors. Finally we calculate the conformational energy penalty of the putative bioactive conformation of our inhibitors and show that this property correlates well with the Aurora A binding affinity.     

The nature of hydrogen bonding in R22(8) crystal motifs – a computational exploration

R²₂(8), a commonly occurring motif in organic crystals, has been examined here through ab initio and density functional theory (DFT) methods. The 11 R²₂(8) motifs reported by Allen et al. have been classified into five types; their structural features, hydrogen-bonding patterns and the kind of interactions stabilising these motifs have been studied. Results reveal that the electronegativity of donor atoms plays a major role in directing the hydrogen bonds, whereas their positions in the motif have been found to be less important. Quantum theory of atoms in molecules (QTAIM) and reduced density gradient-based non-covalent-interaction analyses have been used to understand the weak interactions between monomers. Homonuclear interactions within the motifs have been found to be stronger with higher covalent character at the bond critical points than heteronuclear interactions. In addition, a localised molecular orbital energy decomposition analysis (LMOEDA) has been accomplished to provide useful insight into various long- and short-range interactions that contribute to the total stabilisation energies. The stabilising n → σ* interactions have been explained using natural bond orbital (NBO) analysis. Overall, this study provides the essential criteria for an organic crystal to be in an R²₂(8) motif and further discusses the different combinations of hydrogen-bonding features within the R²₂(8) motifs.     

Effects of quenching on the morphology and crystal structure of ZnO nanostructures

Zinc oxide nanostructures were prepared by a simple wet chemical procedure using zinc acetate and sodium hydroxide as precursors. The process was subjected to quenching treatment and the effect of the treatment on the formation of the nanostructures was studied using atomic force and scanning electron microscopies. The change in crystal structure of the nanostructures due to quenching was studied using an X-ray diffractometry that established that physical and structural properties of the nanostructures were largely influenced by the quenching treatment.     

Fabrication of Ni nanodots templated by nanoporous polysulfone membrane: Structural and Magnetic properties

Two-dimensional nickel nanodots were prepared using a simple polymer based lithography process on silicon substrates. The nanoporous polysulfone membranes were fabricated using a phase inversion polymerization process. Nickel nanodots were then grown using the polysulfone membrane as a mask. The structures were written by depositing a certain thickness of nickel using electron beam evaporation. After lift off, the structural properties of the samples were studied using atomic force microscopy and grazing incidence X-ray diffractometry. The dots were found to have diameters in the range of 75–120 nm and heights of 3–5 nm. The magnetization and magnetic domain arrangement of the Ni nanodots were analyzed using vibrating sample magnetometer and magnetic force microscopy respectively. The nanodots were found to exhibit excellent soft ferromagnetic properties with a preferred easy axis of magnetization.     

<em>Cassia spectabilis </em>(DC) Irwin et Barn: A Promising Traditional Herb in Health Improvement

The genus Cassia, comprising about 600 species widely distributed worldwide is well known for its diverse biological and pharmacological properties. Cassia spectabilis (sin Senna spectabilis) (DC) Irwin et Barn (Fabaceae) is widely grown as an ornamental plant in tropical and subtropical areas. C. spectabilis has been commonly used in traditional medicine for many years. Information in the biomedical literature has indicated the presence of a variety of medicinally-important chemical constituents in C. spectabilis. Pharmacological studies by various groups of investigators have shown that C. spectabilis possesses significant biological activity, such as antibacterial, antibiofilm, antifungal and antioxidant properties. Beside this, toxicity studies of this plant have revealed no toxic effect on mice. In view of the immense medicinal importance of C. spectabilis, this review aimed at compiling all currently available information on C. spectabilis's botany, phytochemistry, pharmacology, and mechanism of actions, toxicology and its ethnomedicinal uses.