Six new triterpenoidal glycosides including two new sapogenols from Albizziae Cortex. V.

Six new triterpenoid glycosides called julibrosides A1-A4, B1 and C1 were isolated from Albizziae Cortex, the dried stem bark of Albizzia julibrissin Durazz. Their structures were determined based on spectral and chemical evidence. Julibrosides B1 and C1 had new sapogenols, designated julibrogenin B and C, respectively, while julibrosides A3 included N-acetyl-D-glucosamine as a sugar component.     

A one-pot access to cycloalkano[1,2-a]indoles through an intramolecular alkyl migration reaction in indolylborates

A novel one-pot protocol for the preparation of cycloalkano[1,2-a]indoles by way of an intramolecular alkyl migration reaction in cyclic indolylborates is described. NaOMe was found to act as a successful trialkylboryl-protecting group against to the lithiation at the C2 of the indole ring. Treatment of cyclic indolylborates with electrophiles produced cycloalkano-[1,2-a]indoles.     

Imaging nanometer metallocatalysts formed by photosynthetic deposition of water-soluble transition-metal compounds

A method of imaging nanometer metallocatalysts formed by photosynthetic precipitation of the water-soluble transition-metal compounds [PtCl(6)](2-) and [RuCl(6)](2-) is reported. Hexachloroplatinate and hexachlororuthenate can accept up to four electrons from Photosystem I (PSI) reaction centers in photosynthetic thylakoid membranes, thereby converting [PtCl(6)](2-) and [RuCl(6)](2-) anions to either metallic platinum (Pt) and ruthenium (Ru) and/or partially oxidized nanometer catalysts at the reducing sides of PSI molecules. Use of this method can potentially create nanometer-sized Pt and/or bimetallic catalysts (such as Pt-Ru) on biomembranes and molecules at pH 7 and room temperature with preservation of the biological function of the molecules.     

First-principle time-dependent study of magnesium-containing porphyrin-like compounds potentially useful for their application in photodynamic therapy

Geometry optimization, singlet-triplet energy gap, and electronic absorption spectra calculation of complexes formed by Mg ion and porphyrin, porphyrazin, chlorine, bacteriochlorine, texaphyrin, phthalocyanine, naphthalocyanine, and anthracocyanine ligands have been carried out to elucidate their potentiality as photosensitizers in photodynamic therapy (PDT). The study has been performed employing the density functional theory (DFT) and its time-dependent approach (TDDFT) in conjunction with the PBE0 exchange-correlation functional and extended TZVP all-electron basis sets. The solvent effects have been evaluated throughout the polarizable continuum model (PCM). Results show that, following the properties requirement for the drugs used in PDT, the Mg-Tex and Mg-Pc complexes are reliable candidates for their use as photosensitizers in this medical therapy.     

Synthesis and Evaluation of the Tetracyclic Ring-System of Isocryptolepine and Regioisomers for Antimalarial,Antiproliferative and Antimicrobial Activities

A series of novel quinoline-based tetracyclic ring-systems were synthesized and evaluated in vitro for their antiplasmodial, antiproliferative and antimicrobial activities. The novel hydroiodide salts 10 and 21 showed the most promising antiplasmodial inhibition, with compound 10 displaying higher selectivity than the employed standards. The antiproliferative assay revealed novel pyridophenanthridine 4b to be significantly more active against human prostate cancer (IC₅₀ = 24 nM) than Puromycin (IC₅₀ = 270 nM) and Doxorubicin (IC₅₀ = 830 nM), which are used for clinical treatment. Pyridocarbazoles 9 was also moderately effective against all the employed cancer cell lines and moreover showed excellent biofilm inhibition (9a: MBIC = 100 µM; 9b: MBIC = 100 µM).     

Catalytic aerobic oxidation of nor-binaltorphimine (nor-BNI) analogs without 4,5-epoxy bridge affords a more selective ligand for kappa opioid receptor than the representative kappa antagonist nor-BNI

An analog of nor-binaltorphimine (nor-BNI) without the 4,5-epoxy bridge, 17,17'-bis(cyclopropylmethyl)-6,6',7,7'-tetrahydro-6,6'-imino-14beta,14'alpha-dihydroxy-3,3'-dimethoxy-7,7'-bimorphinan (4), which was the precursor of the designed compound 1 as a selective kappa(3) opioid receptor antagonist, was catalytically oxidized with oxygen in the presence of platinum to give the 5'-oxo derivative 3 with some other oxidized products. Morphinan derivatives without the 4,5-epoxy moiety were labile to oxygen, although the corresponding 4,5-epoxymorphinan derivatives resisted aerobic oxidation. One of the oxidized nor-BNI analogs without 4,5-epoxy bridge, compound 18, showed high affinity and selectivity for kappa opioid receptor.     

Photoluminescence of perovskite nanosheets prepared by exfoliation of layered oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion)

Luminescent perovskite nanosheets were prepared by exfoliation of single- or double-layered perovskite oxides, K2Ln2Ti3O10, KLnNb2O7, and RbLnTa2O7 (Ln: lanthanide ion). The thickness of the individual nanosheets corresponded to those of the perovskite block in the parent layered compounds. Intense red and green emissions were observed in aqueous solutions with Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets, respectively, under UV illumination with energies greater than the corresponding host oxide band gap. The coincidence of the excitation spectrum and the band gap absorbance indicates that the visible emission results from energy transfer within the nanosheet. The red emission intensity of the Gd1.4Eu0.6Ti3O10-nanosheets was much stronger than that of the La0.90Eu0.05Nb2O7-nanosheets reported previously. The strong emission intensity is a result of a two-step energy transfer cascade within the nanosheet from the Ti-O network to Gd(3+) and then to Eu(3+). The emission intensities of the Gd1.4Eu0.6Ti3O10- and La0.7Tb0.3Ta2O7-nanosheets can be modulated by applying a magnetic field (1.3-1.4 T), which brings about a change in orientation of the nanosheets in solution. The emission intensities increased when the excitation light and the magnetic field directions were perpendicular to each other, and they decreased when the excitation and magnetic field were collinear and mutually perpendicular to the direction of detection of the emitted light.     

Minimised Geometric Buchberger Algorithm for Integer Programming

Recently, various algebraic integer programming (IP) solvers have been proposed based on the theory of Gröbner bases. The main difficulty of these solvers is the size of the Gröbner bases generated. In algorithms proposed so far, large Gröbner bases are generated by either introducing additional variables or by considering the generic IP problem IP _A,C . Some improvements have been proposed such as Hosten and Sturmfels' method (GRIN) designed to avoid additional variables and Thomas' truncated Gröbner basis method which computes the reduced Gröbner basis for a specific IP problem IP _A,C (b) (rather than its generalisation IP _A,C ). In this paper we propose a new algebraic algorithm for solving IP problems. The new algorithm, called Minimised Geometric Buchberger Algorithm, combines Hosten and Sturmfels' GRIN and Thomas' truncated Gröbner basis method to compute the fundamental segments of an IP problem IP _A,C directly in its original space and also the truncated Gröbner basis for a specific IP problem IP _A,C (b). We have carried out experiments to compare this algorithm with others such as the geometric Buchberger algorithm, the truncated geometric Buchberger algorithm and the algorithm in GRIN. These experiments show that the new algorithm offers significant performance improvement.     

Infusion of Variable Chemical Structure to Tune Stacking among Metal-Organic Layers in 2D Nano MOF

Thickness of two-dimensional (2D) metal-organic frameworks (MOFs) govern their intriguing functionalities. Primarily this thickness is controlled by the stacking between the metal-organic layers (MOL). It is observed that until now such modulating factors for stacking efficiency of MOL are not well studied. Here, we report a fundamental hypothesis to comprehend regulation of stacking efficiency among MOLs as a function of chemical structure of organic ligands (dicarboxylic acids and pillar linkers). This basically involves a series of isostructural three-dimensional (3D) MOFs which contain linkers of variable chemical nature that could be depillared to generate 2D stacked MOFs of different thickness. Depending on the linkers, we encountered the formation of single MOL to stacked multiple MOLs as evidenced from atomic force microscopic and other experimental analysis. The present study gives a concrete correlation between the stacking within 2D MOFs (from monolayer to multilayers), and their 3D counter parts, which may provide a thickness tuning pathway for 2D MOFs.