ETUDE STRUCTURALE DU(N,N-DIMETHYLAMINOCARBONYL-l-METHOXYCARBONYL-2-ETHENYL(Z))-2-OXO-2-TETRAMETHYL- 4,4,5,5-DIOXAPHOSPHOLANE-1,3,2. PHENOMENE DE PREFIGURATION A L'ETAT SOLIDE D'UN INTERMEDIAIRE REACTIONNEL PENTACOORDINE

Abstract

Phosphonate 2 is obtained by hydrolysis of the spirophosphorane 1. IR. ¹H and ³¹P NMR spectra confirm the phosphonate structure. However, one question remains about the relative position of the amide group and ester function relative to the phosphonate group. We resolved this difficulty through X-ray crystallography of 2.

Phosphonate 2 structure shows a slightly distorted figure of the spirophosphorane 1 of which it comes from. This observation is quite astonishing because of the many possible carbonyl positions of the new ester function. We can reasonably rationalize this phenomenon as the prefiguration of a pentacoordinated chemical intermediate which permits to explain easily the opposite reaction for the P_IV → P_v way. So, phosphonate 2 structure is in between two pentacoordinate structures.     

Synthetic Studies on 2H-Thiopyran Compounds: A Reinvestigation of the Reaction Between Benzaldehydes and Sodium Sulfide

An investigation regarding the synthesis of 2H-thiopyran compounds from substituted benzaldehydes with sodium sulfide (Na₂S·10H₂O) in aqueous ethanol was carried out. The structural elucidation of the products was performed by spectroscopic methods and in one example as X-ray crystallographic analysis. A plausible mechanistic pathway is also proposed that is entirely different from an earlier report.     

Inequalities involving modified Bessel functions of the first kind II

The intrinsic properties, including logarithmic convexity (concavity), of the modified Bessel functions of the first kind and some other related functions are obtained. Several inequalities involving functions under discussion are established.     

Inhibitory G proteins and their receptors: emerging therapeutic targets for obesity and diabetes

The worldwide prevalence of obesity is steadily increasing, nearly doubling between 1980 and 2008. Obesity is often associated with insulin resistance, a major risk factor for type 2 diabetes mellitus (T2DM): a costly chronic disease and serious public health problem. The underlying cause of T2DM is a failure of the beta cells of the pancreas to continue to produce enough insulin to counteract insulin resistance. Most current T2DM therapeutics do not prevent continued loss of insulin secretion capacity, and those that do have the potential to preserve beta cell mass and function are not effective in all patients. Therefore, developing new methods for preventing and treating obesity and T2DM is very timely and of great significance. There is now considerable literature demonstrating a link between inhibitory guanine nucleotide-binding protein (G protein) and G protein-coupled receptor (GPCR) signaling in insulin-responsive tissues and the pathogenesis of obesity and T2DM. These studies are suggesting new and emerging therapeutic targets for these conditions. In this review, we will discuss inhibitory G proteins and GPCRs that have primary actions in the beta cell and other peripheral sites as therapeutic targets for obesity and T2DM, improving satiety, insulin resistance and/or beta cell biology.     

Purity Considerations and Interfacial Behavior of Solvent Extraction Systems

Abstract

The techniques to purify different components of a typical solvent extraction system, viz., n-hexane/di(2-ethylhexyl)phosphoric acid (HDEHP)/CaCl₂ solution, are described. Data showing how the purity of the different components affects the interfacial tension (γ) are given. The interfacial behavior of the n-hexane/ HDEHP/0.01 mol dm^?3 CaCl₂ solution system was studied as a function of HDEHP concentration and aqueous phase pH. γ-log [HDEHP] curves were also determined at pH 4 when the aqueous phase contained 0.05 mol dm^?3 MgCl₂, CaCl₂, SrCl₂ or BaCl₂. γ-log [HDEHP] curves revealed interaction of the metal ions with the extractant and exhibited a behavior reminiscent of aggregate formation when the aqueous phase contained Ca²⁺.     

CAAC‐Based Thiele and Schlenk Hydrocarbons

Diradicals have been of tremendous interest for over a century ever since the first reports of p‐ and m‐phenylene‐bridged diphenylmethylradicals in 1904 by Thiele and 1915 by Schlenk. Reported here are the first examples of cyclic(alkyl)(amino)carbene (CAAC) analogues of Thiele's hydrocarbon, a Kekulé diradical, and Schlenk's hydrocarbon, a non‐Kekulé diradical, without using CAAC as a precursor. The CAAC analogue of Thiele's hydrocarbon has a singlet ground state, whereas the CAAC analogue of Schlenk's hydrocarbon contains two unpaired electrons. The latter forms a dimer, by an intermolecular double head‐to‐tail dimerization. This straightforward synthetic methodology is modular and can be extended for the generation of redox‐active organic compounds.     

On Equivalence of Linear Functional-Differential Equations

For linear functional-differential equations of the first order there are derived canonical forms and an effective criterion of equivalence with respect to the pointwise transformations.     

An evaluation of three adaptive hearing aid selection strategies

Paired-comparison judgments of intelligibility of speech in noise were obtained from eight hearing-impaired subjects on a large number of hearing aids simulated by a digital master hearing aid. The hearing aids which comprised a 5 X 5 matrix differed systematically in the amount of low-frequency and high-frequency gain provided. A comparison of three adaptive strategies for determining optimum hearing aid frequency-gain characteristics (an iterative round robin, a double elimination tournament, and a modified simplex procedure) revealed convergence on the same or similar hearing aids for most subjects. Analysis revealed that subjects for whom all three procedures converged on the same hearing aid showed a single pronounced peak in the response surface, while a broader peak was evident for the subjects for whom the three procedures identified similar hearing aids. The modified simplex procedure was found to be most efficient and the iterative round robin least efficient.