Polymorphism of (S)-triphenylglycol: kinetic dependent transformation of a new multipolymorphic system

The appearance of six new polymorphic forms of (S)-triphenylglycol and the kinetically dependent transformation observed by DSC by means of quenching from the melt are reported.     

Design and function of pre-organised outer-sphere amidopyridyl extractants for zinc(II) and cobalt(II) chlorometallates: the role of C-H hydrogen bonds

Four new sterically hindered pyridines, L(1)-L(4)-containing amido substituents at the 2-position act as efficient solvent extractants for [CoCl(4)](2-) or [ZnCl(4)](2-) from acidic chloride solutions through protonation of the pyridino N-centre to form the neutral outer-sphere complexes [(LH)(2)MCl(4)]. These ionophores show very high selectivity for chlorometallate anions over chloride ion and are readily stripped to liberate the free-metal chlorides without the formation of inner-sphere complexes [ML(2)Cl(2)]. Single-crystal X-ray structure determinations of [(L(2)H)(2)CoCl(4)] and [(L(2)H)(2)ZnCl(4)] (L(2) = 2-(4,6-di-tert-butylpyridin-2-yl)-N,N'-dihexylmalonamide) coupled with (1)H?NMR spectroscopy and DFT calculations on L(2)H(+) and other complexes of [ZnCl(4)](2-) confirm that the pyridinium NH group does not address the outer co-ordination sphere of the metallanion, but rather forms a hydrogen bond to the pendant amide groups and thus pre-organizes the ligand to present both C-H and amido N-H hydrogen-bond donors to the [MCl(4)](2-) ions. The selectivity for chlorometallates over chloride ions shown by this class of extractants arises from their ability to present several polarized C-H units towards the charge-diffuse ions [MCl(4)](2-), whereas the smaller, "harder" chloride anion prefers to be associated with the amido N-H hydrogen-bond donors.     

Oxyma: An Efficient Additive for Peptide Synthesis to Replace the Benzotriazole‐Based HOBt and HOAt with a Lower Risk of Explosion[1]

Oxyma [ethyl 2‐cyano‐2‐(hydroxyimino)acetate] has been tested as an additive for use in the carbodiimide approach for formation of peptide bonds. Its performance in relation to those of HOBt and HOAt, which have recently been reported to exhibit explosive properties, is reported. Oxyma displayed a remarkable capacity to inhibit racemization, together with impressive coupling efficiency in both automated and manual synthesis, superior to those of HOBt and at least comparable to those of HOAt, and surpassing the latter coupling agent in the more demanding peptide models. Stability assays showed that there was no risk of capping the resin under standard coupling conditions. Finally, calorimetry assays (DSC and ARC) showed decomposition profiles for benzotriazole‐based additives that were consistent with their reported explosivities and suggested a lower risk of explosion in the case of Oxyma.     

Stabilization of interferometric response using a polarization scrambler

This paper shows, theoretically and experimentally, how a polarization scrambler increases the response stability of a fiber Mach–Zehnder interferometer. We have studied the situation when the scrambler is placed in one of the interferometer branches and also when it is placed at the interferometer input. The measurements carried out using a scrambler based on the Faraday effect, agree with the simulation results.     

Design and Function of Pre‐organised Outer‐Sphere Amidopyridyl Extractants for Zinc(II) and Cobalt(II) Chlorometallates: The Role of C?H Hydrogen Bonds

Four new sterically hindered pyridines, L¹–L⁴‐containing amido substituents at the 2‐position act as efficient solvent extractants for [CoCl₄]^2? or [ZnCl₄]^2? from acidic chloride solutions through protonation of the pyridino N‐centre to form the neutral outer‐sphere complexes [(LH)₂MCl₄]. These ionophores show very high selectivity for chlorometallate anions over chloride ion and are readily stripped to liberate the free‐metal chlorides without the formation of inner‐sphere complexes [ML₂Cl₂]. Single‐crystal X‐ray structure determinations of [(L²H)₂CoCl₄] and [(L²H)₂ZnCl₄] (L²=2‐(4,6‐di‐tert‐butylpyridin‐2‐yl)‐N,N′‐dihexylmalonamide) coupled with ¹H NMR spectroscopy and DFT calculations on L²H⁺ and other complexes of [ZnCl₄]^2? confirm that the pyridinium NH group does not address the outer co‐ordination sphere of the metallanion, but rather forms a hydrogen bond to the pendant amide groups and thus pre‐organizes the ligand to present both C? H and amido N? H hydrogen‐bond donors to the [MCl₄]^2? ions. The selectivity for chlorometallates over chloride ions shown by this class of extractants arises from their ability to present several polarized C? H units towards the charge‐diffuse ions [MCl₄]^2?, whereas the smaller, “harder” chloride anion prefers to be associated with the amido N? H hydrogen‐bond donors.     

An Assay for Screening Potential Drug Candidates for Alzheimer's Disease That Act as Chaperones of the Transthyretin and Amyloid-β Peptides Interaction

The protein transthyretin (TTR) modulates amyloid-β (Aβ) peptides deposition and processing and this physiological effect is further enhanced by treatment with iododiflunisal (IDIF), a small-molecule compound (SMC) with TTR tetramer stabilization properties, which behaves as chaperone of the complex. This knowledge has prompted us to design and optimize a rapid and simple high-throughput assay that relies on the ability of test compounds to form ternary soluble complexes TTR/Aβ/SMC that prevent Aβ aggregation. The method uses the shorter Aβ(12–28) sequence which is cheaper and simpler to use while retaining the aggregation properties of their parents Aβ(1–40) and Aβ(1–42). The test is carried out in 96-plate wells that are UV monitored for turbidity during 6 h. Given its reproducibility, we propose that this test can be a powerful tool for efficient screening of SMCs that act as chaperones of the TTR/Aβ interaction that may led to potential AD therapies.     

Two main utility-sharing methods in joint businesses: A discussion

We compare two methods of sharing costs or profits among agents in cooperative games: the well–known proportional rule and the Shapley value. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)