Oxime functionalization strategy for iodinated poly(epsilon‐caprolactone) X‐ray opaque materials

Since two of the most common technologies for imaging the human body are X‐ray radiography and computed tomography (CT), researchers are focused on developing biodegradable and biocompatible polymeric molecules as an alternative to the traditional small molecule contrast agents. This report highlights the synthesis of novel biodegradable iodinated poly(ε‐caprolactone) copolymers by oxime “Click” ligation reactions. A series of ketone‐bearing materials are built by tin (II)‐mediated ring‐opening polymerization followed by a postpolymerization deprotection step. The intended X‐ray opacity is imparted through acid‐catalyzed oxime postpolymerization modification of the resultant polymers with an iodinated hydroxylamine. All small molecules and polymeric materials are characterized using proton nuclear magnetic resonance (NMR) for purity, functional group stoichiometry, and number‐averaged molecular weight calculations. Additionally, the polymers are evaluated with gel permeation chromatography (GPC) to determine polymer sample polydispersity and general molecular weight distribution shapes and by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) for thermal properties. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 2421–2430     

Microwave‐Assisted Beckmann Rearrangement: Convenient Synthesis of 1,3‐Diaza‐bicyclo[3.2.2]nonane

Small heterocyclic amines such as 1,3‐diaza‐bicyclo[3.2.2]nonane are known to be key components of biologically active molecules. A convenient synthesis of this compound utilizing a key Beckmann rearrangement of (Z)‐1‐aza‐bicyclo[2.2.2]octan‐3‐one oxime (6) with conc. H₂SO₄ under microwave irradiation was achieved. The desired compound (1) was obtained in 20% yield overall.     

Synthesis and Characterization of Novel Methacrylate Monomers Having Pendant Oxime Esters and Their Copolymerization with Styrene

New methacrylate monomers, 2‐{[(diphenylmethylene)amino]oxy}‐2‐oxoethyl methacrylate (DPOMA) and 2‐{[(1‐phenylethylidene)ami no]oxy}‐2‐oxoethyl methacrylate (MMOMA) were prepared by reaction of sodium methacrylate with diphenylmethanone O‐(2‐chloroacetyl) oxime and 1‐phenylethanone O‐(2‐chloroacetyl) oxime, respectively. They were obtained from a reaction of chloroacetyl chloride with benzophenone oxime or acetophenone oxime. The free‐radical‐initiated copolymerization of (DPOMA) and (MMOMA) with styrene (St) were carried out in 1,4‐dioxane solution at 65°C using 2,2‐azobisisobutyronitrile (AIBN) as an initiator with different monomer‐to‐monomer ratios in the feed. The monomers and copolymers were characterized by FTIR, ¹H‐ and ¹³C‐NMR spectral studies. The copolymer compositions were evaluated by nitrogen content in polymers. The reactivity ratios of the monomers were determined by the application of Fineman–Ross and Kelen–Tüdös methods. The molecular weights (M¯_w and M¯_n) and polydispersity index of the polymers were determined by using gel permeation chromatography. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increase in the mole fraction of St in the copolymers. The activation energies of the thermal degradation of the polymers were calculated with the MHRK method. Glass transition temperatures of the copolymers were found to decrease with an increase in the mole fraction of DPOMA or MMOMA in the copolymers. The antibacterial and antifungal effects of the monomers and polymers were also investigated on various bacteria and fungi. The photochemical properties of the polymers were investigated by UV and FTIR spectra.     

Synthesis of a new colorimetric receptor based on calix[4]pyrrole binding oxime for selective recognition of fluoride ions

A colorimetric anion sensor α-meso-heptaethylcalix[4]pyrrole-meso-3-aminophenyl-p-nitrobenzaldoxime was synthesised and characterised by various spectroscopic techniques. Anion-binding studies were carried out using UV–vis, and ¹H NMR titrations, revealing that the receptor exhibits selective recognition towards F^?  over other anions. The selectivity for F^?  among the halides is attributed mainly to the hydrogen bond interaction of the receptor with F^? . Receptor showed colour change from colourless to yellow in the presence of tetrabutylammonium fluoride with 1:2 stoichiometry. Cyclic voltammetry studies, carried out in CH₃CN, provided evidence of an anion-dependent electrochemical response with F^?  ion. This response was particularly dramatic in the case of receptor after the addition of ～1 equiv. of F^?  ion.     

Modeling of Selenoprotein Nitrozation: Synthetic Approaches

Model reactions have been carried out to evaluate the question of what kind of links may exist between the biological cycles of nitrogen oxide (NO) and those of selenoproteins, especially the amino acid selenocysteine (Sec). To collect information about the properties of the as-yet unknown selenonitrites (RSeNO) in comparison with the well-known thionitrites, (RSNO), the interaction of nitrosating reagents with a choice of molecular thiols and related selenoles as model compounds have been studied. Selenol nitrosation is clearly preferred in vitro to thiol nitrosation, but selenonitrites are thermally significantly less stable than the related thionitrites, suggesting that selenonitrites may be important, but yet-undetected intermediates in selenoprotein chemistry. Chemical trapping of RSeNO was achieved for the first time by its 1,4-addition to dimethylbutadiene leading to a stable unsaturated oxime.     

Synthesis and Biological Activities of O-Alkyl,O-Aryl,O-{Z-[1-Phenyl-2-(1H-1,2,4-triazol-1-yl)ethylidene]amino} Phosphorothioates

A series of title compounds 2 were efficiently synthesized via the condensation of 1-phenyl-2-(1H-1,2,4-triazol-1-yl)ethanone oxime with various asymmetric thiophosphoryl chlorides in sodium hydroxide powder and acetonitrile system. The structures of title compounds 2 were confirmed by IR, ¹H NMR, ³¹P NMR, EI-MS, and elemental analysis. The results of preliminary bioassays indicated that the title compounds 2 possessed good to moderate insecticidal activity against aphides at the dosage of 250 mg/L, and some of them exhibited moderate fungicidal activities at the concentration of 100 mg/L.     

Catalysis by Amberlyst A-21: A Greener Approach to 4,5,6,7-Tetrahydro-1H-indazol-3(2H)-ones via Construction of Cyclohexanones

The 4,5,6,7-tetrahydro-1H-indazol-3(2H)-one derivatives have been synthesized in good yields via a two-step method in a single pot. The initial step involved the construction of cyclohexanone ring from aromatic aldehydes and β-ketoester in i-PrOH using an inexpensive and reusable catalyst (i.e., Amberlyst A-21) under mild reaction conditions. The utility of this catalyst has been demonstrated in synthesizing a range of cyclohexanone derivatives. The catalyst can be recovered and recycled, which makes this procedure simple, convenient, economically viable, and environmental friendly.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Quantitative 1H NMR spectroscopic determination of the E/Z isomer ratio of the antidepressant drug fluvoxamine for use in pharmaceutical analysis

High‐resolution NMR spectroscopy is a powerful tool in the elucidation of a structure with respect to constitution, configuration and conformation. In recent years, NMR has been increasingly used in quantitative analysis. In this study, we show the ability of ¹H NMR to determine the isomeric composition of the antidepressant drug fluvoxamine. The activity of fluvoxamine resides on the E‐isomer, and the current British Pharmacopoeia limits the content of the Z‐isomer to 0.5%. The NMR method described here is able to determine the content of the Z‐isomer down to the 0.2% level on a total amount of 15 mg of the substance. Copyright © 2002 John Wiley & Sons, Ltd.