Carbon-13 NMR Characterization of an O-Alkylated Derivative of the Theophylline Metabolite 1,3-Dimethyluric Acid

Abstract

The structure of the derivative formed during the reaction of 1,3-dimethyluric acid, the major metabolite of theophylline in humans, with iodopropane was elucidated. GC-MS analysis indicated the presence of a single dipropylated product even though three positional isomers are possible. The stability of the product was lower than anticipated since one of the alkyl groups added was readily removed by acid hydrolysis. Carbon-13 NMR proved to be the most useful technique for establishing the positions of alkylation. Assignment of carbon-13 resonances were consistent with placement of propyl groups on N-7 and on the oxygen at C-8. The structure of the product was assigned as 1,3-dimethyl-7-(1-propyl)-8-(1-propyloxy)xanthine. This O-alkylated structure is unusual since most heterocycles that can exist as lactim-lactam tautomers alkylate primarily on ring nitrogens.     

Two new β-carboline-type alkaloids from Stellaria dichotoma var.lanceolata

Two new β-carboline-type alkaloids,dichotomine K(1) and dichotomine L(2),were isolated from the roots of Chinese medicinal plant Stellaria dichotoma L.var.lanceolata Bge.Structures of 1 and 2 were determined on the basis of chemical and spectroscopic means.     

Hard magnetic properties of nanosized Sr(Fe,Al)12O19 hexaferrites obtained by Pechini method

In this work, we report the magnetic properties of isotropic M-type SrFe_12−xAl_xO₁₉ (x=0.0,1.5) hexaferrites synthesized by means of Pechini method. A polycrystalline distribution of fine grains was verified by Transmission Electron Microscopy for both compositions, with average sizes below 60 nm. Remarkable coercivity values within the range 500–850 kA/m were attained as a consequence of a combined effect of grain size refinement together with an enhancement of the anisotropy field afforded by the incorporation of the Al³⁺ cations into the hexagonal crystal structure.     

Rapid initiation of reactions in Al/Ni multilayers with nanoscale layering

Research into nanoenergetic materials is enabling new capabilities for controlling exothermic reaction rates and energy output, as well as new methods for integrating these materials with conventional electronics fabrication techniques. Many reactions produce primarily heat, and in some cases it is desirable to increase the rate of heat release beyond what is typically observed. Here we investigate the Al-Ni intermetallic reaction, which normally propagates across films or foils at rates lower than 10 m/s. However, models and experiments indicate that local heating rates can be very high (10⁷ K/s), and uniform heating of such a multilayer film can lead to a rapid, thermally explosive type of reaction. With the hopes of using a device to transduce electrical energy to kinetic energy of a flyer plate in the timescale of 100's of nanoseconds, we have incorporated a Ni/Al nanolayer film that locally heats upon application of a large electrical current. We observed flyer plate velocities in the 2-6 km/s range, corresponding to 4-36 kJ/g in terms of specific kinetic energy. Several samples containing Ni/Al films with different bilayer thicknesses were tested, and many produced additional kinetic energy in the 1.1-2.3 kJ/g range, as would be expected from the Ni-Al intermetallic reaction. These results provide evidence that nanoscale Ni/Al layers reacted in the timescale necessary to contribute to device output.     

Structural deformation monitored by vibrational properties and orbital modeling in (Pb,Sm)TiO3 systems

Pb_1−xSm_xTiO₃ (PST) powders with x varying from 0 to 0.1 were obtained by the polymeric precursor method, a soft chemical route. The vibrational properties relating tetragonal to pseudo-cubic phase transition were studied by Raman spectroscopy. The results obtained showed that the phase transition is extremely dependent upon the samarium content and presents a diffuse behavior. Monitoring of the oxygen 2p and titanium 3d orbitals was performed by the periodic mechanical quantum method, revealing the changes that occur with the distribution and contribution of the hybrid orbitals due to the samarium influence.     

Self-assembly and characterization of Ca-Al-LDH nanohybrids containing casein proteins as guest anions

Casein, a natural biopolymer contained in milk, has been successfully intercalated into a Ca-Al-LDH host structure. Synthesis was performed by rehydration of tricalcium aluminate in the presence of casein. The resulting nanohybrids were characterized by powder X-ray diffraction (XRD), elemental analysis, infrared spectroscopy (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further experiments revealed that the single protein strains intercalate instead of the entire casein sub micelles, which are present in milk. Additionally, the pure phospho protein fractions α- and β-casein, which make up ∼80 wt% of total casein were isolated and intercalated into the Ca-Al-LDH host structure, yielding a biopolymer-inorganic hybrid material.     

Synthesis of aqueous dispersion of graphenes via reduction of graphite oxide in the solution of conductive polymer

Graphene sheets were produced by chemical reduction of graphite oxides in the solution of ionic conductive polymer, Nafion. The obtained graphene, coated with Nafion, can be re-dispersed in water, and readily forms stable dispersed state. The polymer-coated graphene had been characterized by FT-IR spectroscopy, UV-vis and X-ray photoelectron spectroscopy (XPS). The PEDOT film with Nafion-coated graphene increased significantly from 0.25 S/cm for pure PEDOT film and reached 12 S/cm. Further, the films of PEDOT doped Nafion-coated graphene had also higher conductivities compared to films doped PSS-coated graphene.     

P-coumaric acid-zinc basic salt nanohybrid for controlled release and sustained antioxidant activity

P-coumaric acid (pCA) has been intercalated in zinc basic salt (ZBS) to design an organic-inorganic nanohybrid material with controlled release and sustained antioxidant activity. According to the powder X-ray diffraction patterns and FT-IR spectra, pCA molecules were intercalated into ZBS without any noticeable alterations in their structural integrity. In vitro release test showed a biphasic discharge of pCA out of the interlayer space of two-dimensional ZBS lattice consisting of an initial burst release followed by a slow and sustained release. The pCA-ZBS nanohybrid exhibited comparable antioxidant activity to that of the free pCA.