Synthesis and spectral properties of 6,7-dimethoxy-1-[(ortho; and para-R)-phenyl]-3,4-dihydroisoquinoline

The preparation of eleven novel 6,7-dimethoxy-1-[(ortho, and para-R)-phenyl]-3,4-dihydroisoquinolines with possible pharmacological activity is described. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr, and ms.     

Improved synthesis of several methoxynitronaphthalenes

Summary An improved procedure for the synthesis of several isomeric methoxynitronaphthalenes is described. The key intermediates in the synthesis are the respective nitronaphthylamines and nitronaphthols. The syntheses of 1-methoxy-3-nitronaphthalene (1), 1-methoxy-5-nitronaphthalene (2), and 2-methoxy-5-nitronaphthalene (3) are reported.Part of this work was carried out at the University of Texas at El Paso, El Paso, TX, during the tenure of one of the authors there (C.P.)     

Determination of the plant growth regulator beta-naphthoxyacetic acid by micellar-stabilized room temperature phosphorescence

This paper presents a method for the determination of the plant growth regulator beta-naphthoxyacetic acid (NOA) by micellar-stabilized room temperature phosphorescence with the surfactant Triton X-100 (TX-100) as the micellar medium, thallium nitrate as the heavy atom and sodium sulphite as the oxygen scavenger. A multivariate optimization approach using the blocked cube star design of central composite was carried out. The analytical curve of NOA gives a linear dynamic range of 0.4-3.0 mug ml(-1) and a detection limit of 0.13 mug ml(-1). A recovery of 93.6% was obtained for 1 mug ml(-1) NOA in spiked apple samples.     

Determination of selenium species in human urine by high performance liquid chromatography and inductively coupled plasma mass spectrometry

A method developed to determine organic and inorganic selenium species in human urine samples is presented in detail. After a simple sample treatment based on elimination of non-charged organic compounds, selenium species were separated by high performance liquid chromatography (HPLC) on a Spherisorb 5 ODS/AMINO column using two different chromatographic conditions: phosphate buffers at pH 2.8 and 6.0. Detection was carried out using an on-line inductively coupled plasma mass spectrometer (ICP-MS). Trimethylselenonium ion and two unknown selenium species in urine samples were found. Selenium species were shown to have stability problems, with the maximum allowed storage time of 1 week.     

Simultaneous determination of multiple constituents in real beer samples of different origins by capillary zone electrophoresis

Simultaneous determination of alcohols, amines, amino acids, flavonoids, and purine and pyrimidine bases in bottled beer samples directly without any pre-treatment was carried out by capillary zone electrophoresis with diode-array detection. Electrolyte conditions such as pH, composition and concentration of the buffer, working voltage and type and time of injection were checked. The best separation of the cited analytes was achieved in 70 mM sodium borate solution and pH 10.25. The detection limits were from 2.1 to 5.6 mg L^–1 for the 18 compounds studied. The developed method is rapid, sensitive and quantitative and has been applied to seven types of international bottled beers of different origins bought locally.     

Sensitive and simple determination of the vasodilator agent dipyridamole in pharmaceutical preparations by phosphorimetry

The applicability of heavy atom-induced room-temperature phosphorescence to pharmaceutical samples is demonstrated in this work. Thus a new, simple, rapid, and selective phosphorimetric method for dipyridamole determination is proposed. The phosphorescence signals are a consequence of intermolecular protection when analytes are exclusively in the presence of heavy atom salts and sodium sulfite as an oxygen scavenger to minimize RTP quenching. The determination was performed in 0.1 mol L^–1 thallium(I) nitrate and 8 mmol L^–1 sodium sulfite at a measurement temperature of 20 °C. The phosphorescence intensity was measured at 635 nm, with excitation at 305 nm. Phosphorescence was easily developed; a linear concentration range was obtained between 0 and 100 ng mL^–1 with a detection limit of 940 ng L^–1, an analytical sensitivity of 2.5 ng mL^–1, and a standard deviation of 2.7% at 60 ng mL^–1 concentration. The method has been successfully applied to the analysis of dipyridamole in a unique Spanish commercial formulation containing 100 ng mL^–1 per capsule. The recovery was 101.6% with 6.5% standard deviation of analytical measurement. The method using the standard addition methodology has been validated.     

Supramolecular architecture and magnetic properties of copper(II) and nickel(II) porphyrinogen-TCNQ electron-transfer salts

The compounds [Cu(Tz)-(MeOH)2](TCNQ)2 (1), [Ni(Tz)-(MeOH)2](TCNQ)2 (2), [Cu(Tz)2]-(TCNQ)7 (3) and [Ni(Tz)2](TCNQ)7 (4) (Tz = 2,7,12,17-tetramethyl-1,6,11,16-tetraazaporphyrinogen) were obtained by metathesis reaction of [M(Tz)](ClO4)2 with LiTCNQ and Et3NH(TCNQ)2, respectively. They were characterized by a combination of spectroscopic and physical methods. Compound 1 crystallizes in the monoclinic space group P2(1)/n with a = 8.310(2), b = 25.180(4), c = 20.727(4) A, beta = 93.58(2) degrees; Z = 4. Compound 3 crystallizes in the triclinic space group P1 with a = 11.244(1), b = 16.700(1), c = 17.321(1) A, a = 113.47(1), beta = 108.52(1), gamma = 96.12(1) degrees; Z = 2. The asymmetric unit of the compound 1 is formed by cationic [Cu(Tz)(MeOH)2]2+ and by two crystallographically non equivalent TCNQ.- anions; these anions form dimeric units by overlap of the pi clouds. The dimers form hydrogen bonds with the metal-lomacrocyclic cation through the methanol ligands. According to this structure the compound is paramagnetic and behaves as an insulator in the temperature range studied. The paramagnetism arises only from the metal-complex moieties. Compound 3 shows an unprecedented structure due to the steric requirements of the macrocycle that favors the stacking of the TCNQ groups. The structure consists of infinite stacks of TCNQ units separated by the metal-macrocyclic units; there are seven TCNQ molecules per formula unit, one of which is formally mono-anionic, while the other six bear one half of an electron per molecule. The copper is six-coordinate in a very distorted octahedral environment. The Tz ligand is located in the equatorial plane and the apical nitrogens of the nitrile groups of two TCNQ molecules complete the coordination around the copper. The compound is a semiconductor and its magnetic behavior can be explained by the sum of the Curie contribution of the metal complex and the contribution arising from the magnetic-exchange interactions of the spins located on the TCNQ units. The latter is found to be typical of one-dimensional antiferromagnetic distorted chains of S = 1/2 spins and can be fitted according to a one-dimensional Heisenberg antiferromagnetic model.     

Interaction of surfactants with thickeners used in waterborne paints: a rheological study

Studies of the phase diagram and linear viscoelasticity of aqueous solutions of hydrophobically modified hydroxyethyl cellulose (HMHEC), a thickener used in water-based paints, and SDS reveal that SDS-HMHEC mixed micelles are formed that increase the number of hydrophobic junctions and enhance interpolymer association up to an [SDS]/[HMHEC] ratio. This fact produces a strong increase of viscoelasticity or a phase separation, depending on the [HMHEC]. At higher ratios the excess of micelles with predominant SDS isolates hydrophobes and disrupts the micellar network. Then, viscoelastic functions decrease and HMHEC behaves as a nonassociative polymer. TTAB and Brij30 also interact with HMHEC, but in a different way. No phase separation is observed with these surfactants. TTAB forms mixed micelles and new junction points in the same way as SDS. However, this surfactant does not stabilize the micelles as SDS does, presumably due to the different interaction between the OH from the cellulose and the charged groups. Results seem to indicate that Brij30 enters into the hydrophobic aggregates of HMHEC and stabilizes them, increasing relaxation time, but it does not form new junction points, since it forms quite big micelles.     

High speed liquid chromatography for in-process control of rifabutin

A fast HPLC method has been developed for simultaneous determination of rifabutin and its synthesis precursors. The analytes are separated in 1.8 min by means of a Kromasil 100 C₁₈ column (50 mm × 2.1 mm i.d., 3.5 μm) at 30 °C. The mobile phase (A: 5 mM KH₂PO₄ adjusted to pH 6.5 with KOH; B: acetonitrile) was pumped at a flow rate of 0.4 ml min⁻¹ according to the fast gradient mode: 0 min, 58% B; 0-0.4 min, 95% B. Detection was by ultraviolet absorbance at 275 nm. The method was validated in accordance with the International Conference on Harmonisation (ICH) guidelines and good accuracy, intermediate precision (≤4.6%) and linearity in the range 5-50 mg l⁻¹ were observed for all compounds. This method is sensitive (limits of detection ranged between 0.1 and 0.3 mg l⁻¹) and selective to quantify rifabutin and its synthesis precursors and could be used for in-process control.     

Preference of di-n-butyltin compounds to build O?Sn bonds in fused rings with five-six members

The reaction of salicylaldehyde (1), o-aminophenols (2a-2f), and di-n-butyltin^IV oxide (3) to give six di-n-butyltin^IV compounds (4a-4f) was achieved in good yields. All compounds were characterized by ¹H, ¹³C, ¹⁵N, ¹¹⁹Sn NMR, mass spectrometry, IR, elemental analysis and in the case of compounds 4a, 4b, 4d and 4e by X-ray diffraction analysis. Compound 4a crystallized with trigonal bipiramidal (TPB) geometry surrounding the tin atom while 4b and 4e crystallized as dimeric molecules joined by two O?Sn bonds with distorted octahedron (DOC) geometry. The X-ray structure of 4d presents one cocrystallized monomeric TBP with one dimeric DOC molecule. Correlations of σ_Hammett vs. spectroscopic values were found for 4a-4b and 4d-4f, indicating the substituents in the aromatic ring derived from o-aminophenol serve as modulators of the O?Sn supramolecular interaction. The O?Sn bond formation is selective for the five-membered ring oxygen atom.