Syntheses of symmetric and unsymmetric 2,6‐bis(phosphino)phenols

Compounds bearing the structural motif of 2,6‐bis(phosphino)phenol have been synthesized via two general methods. Double lithium‐halogen exchange occurred in low‐temperature reactions of O‐protected (by methyl‐ or tetrahydropyranyl groups) 2,6‐dibromo‐4‐methylphenol derivatives with BuLi (2 equivalents); quenching the reaction mixtures with chlorophosphines ClPR₂ (R = Ph, ⁱPr) and corresponding O‐deprotection yielded symmetrically substituted 2,6‐bis(phosphino)phenols. Sequential incorporation of  PR₂ functionalities was accomplished via single lithium‐halogen exchange (1 eq. of BuLi) of tetrahydropyranyl‐protected 2,6‐dibromo‐4‐methylphenol followed by ClPR₂ quenches, thus enabling the syntheses of unsymmetric 2,6‐bis(phosphino)phenols. Such compounds were also obtained via sequential ortho‐lithiations of tetrahydropyranyl‐protected 4‐tert‐but ylphenol, followed by ClPR₂ quenches. All of the new compounds have been characterized by spectrometric methods (¹H and ³¹P NMR, and mass spectrometry). In addition, two of the compounds, 1‐(diphenylphosphino)‐3‐(diphenylphosphoryl)‐2‐methoxy‐5‐methylbenzene ( 3a‐ox ) and 1,3‐bis(diphenylphosphino)‐2‐methoxy‐5‐methylbenzene ( 6a ) have also been characterized via single crystal X‐ray diffraction experiments. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:656–663, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20251     

The iodine atom transfer addition reaction (I‐ATRA) initiated by AIBN: Optimization,scope and radical reaction pathways

Optimization of reaction conditions (alkene, halide, solvent, stoichiometry, manners of the reagents addition, and reaction time) of the I‐ATRA reactions involving 1‐iodoalkylphosphonates was carried out. GC–MS–CI/EI analyses showed main and side products of this reaction and the corresponding radical reaction pathways leading to products derived from phosphorus and nonphosphorus containing iodides, as well as explained the source of hydrogen in radical reduction processes accompanying the I‐ATRA reaction. Synthesis of some 3‐iodoalkyl and 3‐iodoalkenylphosphonates was also presented based on the optimized procedure. © 2006 Wiley Periodicals, Inc. Heteroatom Chem 17:22–35, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/hc.20187     

Determination of some thiophosphorus insecticides based on coulometric titration with the anodically generated chlorine: a further insight in the reaction mechanism in aqueous medium

A new method of analytical determination of some thiolo (PS) and thiono (PS) group containing phosphorus insecticides using a coulometric titration with the anodically generated chlorine and biamperometric end-point detection was described. The method worked well for compounds containing one (methamidophos) or two PS bonds (iso-malathion) or one PS bond (fenitrothion) but failed for compounds containing both PS and PS bonds (malathion, dimethoate) or additional sterically hindered CSC bond (fenthion). Based on the found number z of electrons transferred per mol of oxidized compounds, mechanistic pathways for chlorination of PS and PS containing thiophosphorus insecticides with molecular chlorine in aqueous, acidic medium were proposed.     

EPR spectra of γ-irradiated dl-α-alanine supported on molecular sieves

The aim of the work was to collect information concerning boundary effects which are suspected in α-alanine dosimeters consisted of powdered microcrystalline α-alanine and binders. In our experiments the conventional binders were replaced by molecular sieves (MS). MS are inorganic porous materials (host structures) with well organized and uniform intra-crystalline pore systems of nano-scale size. The guest molecules can be either physically adsorbed on very large inner MS surface, or chemically bound to the active sites. They can be also encapsulated inside the intracrystalline cavities. The EPR spectra of gamma irradiated dl-α-alanine supported on NaY, CeY, SOD, mordenite, ZSM-5 and ALPO₄-5 were very similar to that one observed for irradiated microcrystalline dl-α-alanine. In the case of alanine supported on HY an initial EPR spectrum was different and only after some weeks it made resemble to the well known quintet observed in microcrystalline samples. In sodalites synthesized in the presence of dl-α-alanine EPR signal appeared in non-irradiated sample was very low and structureless. The irradiated sample showed a distinct spectrum which was quite different from that one observed for crystalline dl-α-alanine.     

Modulation of the MOP Receptor (μ Opioid Receptor) by Imidazo[1,2-a]imidazole-5,6-Diones: In Search of the Elucidation of the Mechanism of Action

The μ-opioid receptors belong to the family of G protein-coupled receptors (GPCRs), and their activation triggers a cascade of intracellular relays with the final effect of analgesia. Classical agonists of this receptor, such as morphine, are the main targets in the treatment of both acute and chronic pain. However, the dangerous side effects, such as respiratory depression or addiction, significantly limit their widespread use. The allosteric centers of the receptors exhibit large structural diversity within particular types and even subtypes. Currently, a considerable interest is aroused by the modulation of μ-opioid receptors. The application of such a technique may result in a reduction in the dose or even discontinuation of classical opiates, thus eliminating the side effects typical of this class of drugs. Our aim is to obtain a series of 1-aryl-5,6(1H)dioxo-2,3-dihydroimidazo[1,2-a]imidazole derivatives and provide more information about their activity and selectivity on OP3 (MOP, human mu opioid receptor). The study was based on an observation that some carbonyl derivatives of 1-aryl-2-aminoimidazoline cooperate strongly with morphine or DAMGO in sub-threshold doses, producing similar results to those of normal active doses. To elucidate the possible mechanism of such enhancement, we performed a few in vitro functional tests (involving cAMP and β-arrestin recruitment) and a radioligand binding assay on CHO-K1 cells with the expression of the OP3 receptor. One of the compounds had no orthosteric affinity or intrinsic activity, but inhibited the efficiency of DAMGO. These results allow to conclude that this compound is a negative allosteric modulator (NAM) of the human μ-opioid receptor.     

Effect of Black Cumin Cake Addition on the Chemical Composition,Glycemic Index,Antioxidant Activity,and Cooking Quality of Durum Wheat Pasta

Pasta is a good carrier for plant enrichment substances due to its popularity among consumers. The purpose of the study was to investigate the functional potential and optimize the recipe of pasta made from durum semolina with the addition of black cumin cake at the level of 5, 10, 15, 20, and 25%. The use of black cumin cake resulted in a statistically significant (p ≤ 0.05) increase in the content of protein, fat, ash, and fiber, including both the insoluble and soluble fractions. A reduction in the digestible carbohydrate content, in vitro starch hydrolysis index (HI), was observed. Pasta with a reduced glycemic index (GI) compared to the semolina control was obtained. The content of polyphenols, including flavonoids, in the cake-enriched pasta increased significantly (p ≤ 0.05), which resulted in higher antioxidant activity against DPPH. The increase in the iron content was over 2.5 times higher in the sample with the 25% addition of black cumin cake than in the control sample. The functional addition significantly (p ≤ 0.05) increased the loss of dry matter and influenced the cooking time of pasta.     

A comparison of reactivity of (EtO)2P(O)CH2I with related non‐phosphorus‐containing iodides in the radical iodine atom transfer addition

Based on competitive reactions and ¹H NMR measurements, it was found that (EtO)₂P(O)CH₂I is at least 2–3 orders of magnitude less reactive than other non‐phosphorus iodides of the EWG‐CH₂I type (EWG = NC, COOMe, 4‐Br‐C₆H₄CO). MeSCH₂I turned out to be totally unreactive in the title reaction. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:186–188, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10121