Total synthesis of 1-(Z)-atractylodinol

The total synthesis of 1-(Z)-atractylodinol, a natural polyacetylenic alcohol with several biological activities, has been achieved using a newly developed telluride synthon and a novel use for the Negishi type coupling reaction employing vinyl tellurides.     

Identification of a Prenyl Chalcone as a Competitive Lipoxygenase Inhibitor: Screening,Biochemical Evaluation and Molecular Modeling Studies

Cyclooxygenase (COX) and lipoxygenase (LOX) are key targets for the development of new anti-inflammatory agents. LOX, which is involved in the biosynthesis of mediators in inflammation and allergic reactions, was selected for a biochemical screening campaign to identify LOX inhibitors by employing the main natural product library of Brazilian biodiversity. Two prenyl chalcones were identified as potent inhibitors of LOX-1 in the screening. The most active compound, (E)-2-O-farnesyl chalcone, decreased the rate of oxygen consumption to an extent similar to that of the positive control, nordihydroguaiaretic acid. Additionally, studies on the mechanism of the action indicated that (E)-2-O-farnesyl chalcone is a competitive LOX-1 inhibitor. Molecular modeling studies indicated the importance of the prenyl moieties for the binding of the inhibitors to the LOX binding site, which is related to their pharmacological properties.     

Structure and Dynamics of Oligonucleotides in the Gas Phase

By combining ion‐mobility mass spectrometry experiments with sub‐millisecond classical and ab initio molecular dynamics we fully characterized, for the first time, the dynamic ensemble of a model nucleic acid in the gas phase under electrospray ionization conditions. The studied oligonucleotide unfolds upon vaporization, loses memory of the solution structure, and explores true gas‐phase conformational space. Contrary to our original expectations, the oligonucleotide shows very rich dynamics in three different timescales (multi‐picosecond, nanosecond, and sub‐millisecond). The shorter timescale dynamics has a quantum mechanical nature and leads to changes in the covalent structure, whereas the other two are of classical origin. Overall, this study suggests that a re‐evaluation on our view of the physics of nucleic acids upon vaporization is needed.     

Calculating the Maximum Density of the Surface Packing of Ions in Ionic Liquids

Russian Journal of Physical Chemistry A - The maximum density of monolayer packing on a graphene surface is calculated by means of molecular dynamics (MD) for ions of characteristic size and...     

Aqueous Barbier allylation of aldehydes mediated by tin

The aqueous tin-mediated Barbier reaction affords good to excellent yields and moderate syn diastereoselectivity under basic and acidic conditions. The high yields and stereoselectivity observed in the case of o-substituted aldehydes suggest a cyclic organotin intermediate or transition state in K2HPO4 solution. A practical and efficient aqueous tin allylation of methoxy- and hydroxybenzaldehydes can be carried out in HCl solution in 15 minutes to afford the corresponding homoallylic alcohols in high yields. Aliphatic aldehydes give moderate to excellent yields with reaction times ranging from 30 to 60 minutes. Under these conditions, crotylation gives exclusively the gamma-product and the syn isomer is formed preferentially. For 2-methoxybenzaldehyde, an equilibration of the isomers to a syn/anti ratio of 1:1 can be observed after several hours. Control experiments with radical sources or scavengers give no support for radical intermediates. NMR studies suggest a mechanism involving an organotin intermediate. The major organotin species formed depends on the reaction medium and the reaction time. The use of acidic solution reduces the reaction times, due to the acceleration of the formation of the allyltin(IV) species.     

Impedance study of adsorption of iodide ions at Cd(0001) and Bi(111) electrode from various solutions with constant ionic strength

Adsorption of iodide ions at the Bi(111) and Cd(0001) electrodes from the aqueous solutions with constant ionic strength 0.1x M KI + 0.1(1−x) M KF and 0.1x M KI + 0.033(1−x) M K₂SO₄ has been studied by impedance spectroscopy. It was found that, to a first approximation, the classical Frumkin–Melik–Gaikazyan equivalent circuit with the slow diffusion-like and adsorption steps can be applied for fitting the experimental impedance data for iodide ions adsorption on Bi(111) and Cd(0001) from aqueous solutions with constant ionic strength. The modified Grafov–Damaskin circuit can be used in the region of electrode potentials, where parallel faradic processes (electroreduction of protons, oxygen traces) are probable. The more complicated Ershler equivalent circuit, taking into account the slow diffusion-like, adsorption and charge transfer steps, is not applicable for characterization of the adsorption process of I⁻ at Bi(111) and Cd(0001) electrodes.     

Organotin(IV)‐Loaded Mesoporous Silica as a Biocompatible Strategy in Cancer Treatment

The strong therapeutic potential of an organotin(IV) compound loaded in nanostructured silica (SBA‐15pSn) is demonstrated: B16 melanoma tumor growth in syngeneic C57BL/6 mice is almost completely abolished. In contrast to apoptosis as the basic mechanism of the anticancer action of numerous chemotherapeutics, the important advantage of this SBA‐15pSn mesoporous material is the induction of cell differentiation, an effect unknown for metal‐based drugs and nanomaterials alone. This non‐aggressive mode of drug action is highly efficient against cancer cells but is in the concentration range used nontoxic for normal tissue. JNK (Jun‐amino‐terminal kinase)‐independent apoptosis accompanied by the development of the melanocyte‐like nonproliferative phenotype of survived cells indicates the extraordinary potential of SBA‐15pSn to suppress tumor growth without undesirable compensatory proliferation of malignant cells in response to neighboring cell death.     

Binuclear dichlorido(η6‐p‐cymene)ruthenium(II) complexes with bis(nicotinate)‐ and bis(isonicotinate)‐polyethylene glycol ester ligands

Neutral binuclear ruthenium complexes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 of the general formula [{RuCl₂(η⁶‐p‐cym)}₂ μ‐(N^∩N)] (N^∩N = bis(nicotinate)‐ and bis(isonicotinate)‐polyethylene glycol esters: (3‐py)COO(CH₂CH₂O)_nCO(3‐py) and (4‐py)COO(CH₂CH₂O)_nCO(4‐py), n =1–4), as well as mononuclear [RuCl₂(η⁶‐p‐cym)((3‐py)COO(CH₂CH₂OCH₃)‐κN)], complex 9 , were synthesized and characterized using elemental analysis and electrospray ionization high‐resolution mass spectrometry, infrared, ¹H NMR and ¹³C NMR spectroscopies. Stability of the binuclear complexes in the presence of dimethylsulfoxide was studied. Furthermore, formation of a cationic complex containing bridging pyridine‐based bidentate ligand was monitored using ¹H NMR spectroscopy. Ligand precursors, polyethylene glycol esters of nicotinic ( L1 · 2HCl– L4 · 2HCl and L9 · HCl) and isonicotinic acid dihydrochlorides ( L5 · 2HCl– L8 · 2HCl), binuclear ruthenium(II) complexes 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 and mononuclear complex 9 were tested for in vitro cytotoxicity against 518A2 (melanoma), 8505C (anaplastic thyroid cancer), A253 (head and neck tumour), MCF‐7 (breast tumour) and SW480 (colon carcinoma) cell lines. Copyright © 2014 John Wiley & Sons, Ltd.