Synthesis and NMR studies of thiazolidine-4-carboxylic acid derivatives containing a nitro ester function

The preparation of thiazolidine-4-carboxylic acid derivatives containing a 2-nitrooxyethylamine group, potentially active as vasodilators, is reported. Their ¹H nmr studies carried out to establish the configuration of the C2 stereocenter and the full assignment of their ¹H and ¹³C nmr spectra, are also reported.     

Complete spectroscopic structural characterization of novobiocin,isonovobiocin, decarbamylnovobiocin, 2″-(o-Carbamyl)novobiocin,and novobiocin-2″,3″-carbonate

The rigorous structural characterization of novobiocin, is reported using mass spectrometric, infrared and nmr spectroscopic analysis. Complete nmr assignments are reported. Previous reports in the literature had left some quaternary carbon resonances unassigned. Isonovobiocin and decarbamylnovobiocin, although known in the literature for a number of years, have never been completely characterized. Mass spectrometric fragmentation pathways and complete ¹H and ¹³C nmr assignments are reported for these congeners for the first time. The mass spectral fragmentation pathway and nmr assignments are also reported for 2″-(O-carbamyl)novobiocin although the nmr assignments at lower field were reported previously. The structural characterization of novobiocin-2″,3″-carbonate observed in the Test Assay procedure used for Novobiocin is reported for the first time.     

Term isotope shift of high lying odd and even energy levels of Nd II

The isotope shifts of the odd and even parity energy levels of singly-ionised neodymium (Nd II) have been evaluated using the measurements carried out in more than 300 spectral lines of Nd II in the region 3290–5820 Å. Term shift, ΔT (¹⁴⁴Nd-¹⁵⁰Nd), is being reported for 23 low even and 15 high lying even parity levels of Nd II. ΔT for a level of 4f ³6s6p configuration and 8 even levels between 36892 and 43212 cm^-1 are being reported for the first time. ΔT values of 151 high lying odd parity levels are being reported and compared with some of the available earlier reported values. ΔT values of 47 odd parity levels are being reported for the first time, most of which are based on our isotope shift studies in UV region. The electronic configuration assignments to energy levels of Nd II by earlier workers are discussed on the basis of present ΔT values. Electronic configurations to some of the unclassified high lying odd levels have been suggested; the levels with ΔT (144–150) between 300mK and 380mK are assigned to 4f ³5d6s configuration whereas a level with ΔT value of 60mK to 4f46p configuration.     

Preparation and complete 1 H and 13C assignment of some pentacyclo[5.4.0.02,6.03,10.05,9]undecane‐8,11‐dione (PCUD) derivatives

The preparation of a number of alkyl and alkoxy derivatives of pentacyclo[5.4.0.0^2,6.0^3,10.0^5,9]undecane‐8,11‐dione derivatives utilising a cheap, practical, low energy, ‘green’, single‐pass continuous flow photochemical reactor is reported. Their ¹ H and ¹³C NMR spectra are fully assigned, revealing some general characteristics not previously reported for this class of compound, which should aid the assignment and prediction of the NMR spectra of PCUD derivatives. Copyright © 2012 John Wiley & Sons, Ltd.     

The Synthesis of 4,5-Acetylenic Prostaglandins

The synthesis of cis-Δ⁴ prostaglandins has been reported.¹ The conversion of these Δ⁴ analogs to 4,5-acetylenic prostaglandins can be accomplished via the bromination-dehydrobromination procedure reported earlier.² A new approach to the synthesis of 4,5-acetylenic prostaglandins via readily available intermediate has been developed. We wish to report herein this general approach.³     

High-resolution 13C and 43Ca solid-state NMR and computational studies of the ethylene glycol solvate of atorvastatin calcium

We report ⁴³Ca and ¹³C solid-state nuclear magnetic resonance (NMR) spectroscopic studies of the ethylene glycol solvate of atorvastatin calcium. The ¹³C and ⁴³Ca chemical shift and ⁴³Ca quadrupolar coupling tensor parameters are reported. The results are interpreted in terms of the reported X-ray diffraction crystal structure of the solvate and are compared with the NMR parameters of atorvastatin calcium trihydrate, the active pharmaceutical ingredient in Lipitor®. Hartree–Fock and density functional theory calculations of the NMR parameters based on a cluster model derived from the optimized X-ray diffraction crystal structure of the ethylene glycol solvate of atorvastatin calcium are in reasonable agreement with the experimental ⁴³Ca and ¹³C NMR measurables.     

Mechanochemical Activation of Zinc and Application to Negishi Cross‐Coupling

A form independent activation of zinc, concomitant generation of organozinc species and engagement in a Negishi cross‐coupling reaction via mechanochemical methods is reported. The reported method exhibits a broad substrate scope for both C(sp³)–C(sp²) and C(sp²)–C(sp²) couplings and is tolerant to many important functional groups. The method may offer broad reaching opportunities for the in situ generation organometallic compounds from base metals and their concomitant engagement in synthetic reactions via mechanochemical methods.     

19F-detected dual-optimized inverted 1JCC 1,n-ADEQUATE

Modification of the recently reported ¹⁹F-detected 1,1-ADEQUATE experiment that incorporates dual-optimization to selectively invert a wide range of ¹J_CC correlations in a 1,n-ADEQUATE experiment is reported. Parameters for the dual-optimization segment of the pulse sequence were modified to accommodate the increased size of ¹J_CC homonuclear coupling constants of poly- and perfluorinated molecules relative to protonated molecules to allow broadband inversion of the ¹J_CC correlations. The observation and utility of isotope shifts are reported for the first time for 1,1- and 1,n-ADEQUATE correlations.     

Structural Revision and Elucidation of the Biosynthesis of Hypodoratoxide by 13C,13C COSY NMR Spectroscopy

Feeding of (2,3,4,5,6‐¹³C₅)mevalonolactone to the fungus Hypomyces odoratus resulted in a completely labeled sesquiterpene ether. The connectivity of the carbon atoms was easily deduced from a ¹³C,¹³C COSY spectrum, revealing a structure that was different from the previously reported structure of hypodoratoxide, even though the reported ¹³C NMR data matched. A structural revision of hypodoratoxide is thus presented. Its absolute configuration was tentatively assigned from its co‐metabolite cis‐dihydroagarofuran. Its biosynthesis was investigated by feeding of (3‐¹³C)‐ and (4,6‐¹³C₂)mevalonolactone, which gave insights into the complex rearrangement of the carbon skeleton during terpene cyclization by analysis of the ¹³C,¹³C couplings.     

Linear and angular annelation effects on the 13C NMR spectra of tricyclic aromatic ketones. 1—annelated indanones

Carbon-13 NMR chemical shifts are reported for nine tricyclic aromatic ketones formally derived from indanone. The influences of remote ring size, as well as linear, angular exo and angular endo ketone orientation are examined. Results are compared with available ¹H NMR data. For indanone itself, based on selective ¹H decoupling experiments, a recently reported CIDNP derived ¹³C signal assignment is shown to be in error.     

One decade of research on ion-selective electrodes in Iran (1996–2006)

This review presents a general overview about the development of ion-selective electrodes in Iran during the past decade (1996–2006). All of the reported ion-selective sensors (for cations, anions and organic species) are cited in this review. Sensors for 39 cations, 12 anions, and 23 organic compounds and drugs have been reported in this reivew. Some of the main group cations (e.g. beryllium) as well as most of the lanthanide ion (i.e., presidium, erbium, lutetium, cerium, neodymium, europium, gadolinium, terbium, dysprosium, holmium, ytterbium, and thulium) sensors have been reported for the first time. It is noticable that the best reported sensors for HPO₄ ^2?, SO₄ ^2?, Cl^?, ClO₄ ^?, Br^?, and I₃ ^? have been designed and constructed by the Iranian researchers.     

Allowed transitions and intercombination lines in B II

Systematic multiconfiguration results are reported for the 2s ^{2 1} S ₀ → 2s2p ³ P ₁ intercombination line in B II. Both Breit-Pauli and fully relativistic calculations have been performed. The two methods are compared and the results are found to be in good agreement. Length and velocity forms of the oscillator strengths of related allowed transitions are also reported. The latter are used as a check on accuracy along with term energy separation. Fine-structure splitting is also reported but shown not to be a check on accuracy in the Breit-Pauli approximation.     

Renner spliting in the first ionized state of BeF2

The splitting of the ²Π_g state of BeF₂⁺ into the ²B₂ and ²A₂ components has been investigated theoretically by ab initio UHF calculations. The ²A₂ component is found to be linear, and the ²B₂ state is calculated to have minima at bond angles of 180° and ≈100°, with the bent conformation lying lower. Analysis of a possible interaction between two states of ²B₂ symmetry is made. Electron binding energies and symmetric bending force constants are reported. For comparison, a parallel investigation is reported on the analogous states of the isoelectronic CO₂⁺.     

Nuclear magnetic resonance studies: VII—13C and 15N n.m.r. of diazo compounds

The ¹³C and ¹⁵N n.m.r. results for a series of diazo compounds are reported. It is found that the diazo carbon is shielded by an extraordinary amount compared with normal sp² hybridized carbons. The ¹⁵N chemical shifts reveal that the terminal nitrogen is deshielded relative to the central one. This is contrary to that expected from charge effects but support is found for this phenomenon in other systems. One-bond ¹³C? ¹⁴N coupling in diazomethane is also reported for the first time. INDO MO calculations of the charges and finite perturbation calculations of ¹³C? ¹⁴N and C? H couplings are compared with the experimental results.     

Characterisation of the seasonal exposure to air pollutants for a respiratory epidemiological study

In 2006, elementary schools of inner-city Lisbon, Portugal were given questionnaires to identify respiratory problems. In 1,175 children aged 5–10 years, 27.7% reported rhinitis, 2.5% reported hay fever and 25.9% reported asthma symptoms. April and August were the months with higher incidence of rhinitis, with a considerable difference nonetheless (10.5% and 2.3%, respectively.). The former trends are addressed here by using meteorological data, PM_2.5, and its elemental speciation. Mann-Whitney U-tests were applied to the data sets. Significantly higher values were found for humidity, K⁺, NH₄ ⁺, Sb and Zn in April, and for temperature, Cl⁻, Mg²⁺ and Na⁺ in August. Commuter and heavy-duty traffic may contribute to rhinitis episodes.     

Determination of chlorite at very low levels by using differential pulse polarography

A method is reported for the determination of μgl^?1 levels of chlorite by using differential pulse polarography. The electrochemical reduction of chlorite was studied between pH 3.7 and 14 and in an ionic strength range of 0.05–3.0 M. The optimum conditions are pH 4.1–4.4 and an ionic strength of 0.45 M. The current under these conditions is diffusion-controlled and is a linear function of chlorite concentration ranging from 2.77×10^?7 to 2.80×10^?4 M (19 μgl^?1 to 19 mg l^?1). The imprecision is better than ±1.0% and ±3.4% at concentrations of 2.87×10^?5 M and 1.74×10^?6M, respectively, with a detection limit of 1×10^?7 M (7μgl^?1). An interference study and the application of this method for determining chlorite in drinking water are reported.     

A Facile Preparation of the Ethylene Glycol Mono-Ketal of Cyclohexane-1, 4-Dione

The ethylene glycol mono-ketal of cyclohexane-1,4-dione (4) is an exceedingly useful bifunctional synthetic intermediate. In order to prepare synthetically useful amounts of the previously reported ¹ pyrrolidine enamine 5, we have developed a straightforward route which starts from cyclohexane-1,4-diol (1). We have found that oxidation of diol 1 with slightly less than 1 equivalent of Jones reagent² gives a mixture which contains a 90% yield of the desired hydroxy-ketone 2.³ The ketal 3 could be prepared directly from the crude hydroxy-ketone 2 by the standard procedure employing ethylene glycol and benzene with minimal extractive work up. We utilize a chromium trioxide-pyridine oxidation⁴ of the alcohol 3 to obtain the ketone-ketal 4. This procedure circumvents the problem caused by the high water solubility of intermediates 2 and 3 which frustrate some of the previously reported preparations.     

Novel heterocyclic systems. Part 27. The synthesis of various diazathianthrenes and the discrimination of isomeric structures using 13C-NMR and lanthanide induced shift data

Syntheses of the previously unknown 1,7-1,8- and 1,9-diazathianthrenes are reported. The former two systems were prepared via the condensation of the dianion of 2,3-dimercaptopyridine with 3-chloro-4-nitropyridine 1-oxide while the latter employed 2-chloro-3-nitropyridine. The preparation of the 1,9-diazathianthrene also led to the formation of the previously reported 1,6-diazathianthrene as a by-product in a 22% yield. The new ring systems were characterized by a combination of ¹³C nmr and ¹H lanthanide-induced shifts using Eu(fod)₃.     

Total synthesis and structure revision of petrobactin

The total synthesis and the revised structural assignment of petrobactin, a siderophore isolated from the marine bacterium Marinobacter hydrocarbonoclasticus, is reported. The key step in the synthesis involved condensation of N¹-(2,3-dibenzoyloxybenzoyl)-N⁴-benzylspermidine with 1,3-di-(p-nitrophenyl)-2-tert-butyl citrate. Proton NMR spectra of the synthesized product compared with those reported for the natural product revealed that the compound did not contain 2,3-dihydroxybenzoyl moieties as published; instead, the splitting pattern suggested 3,4-dihydroxybenzoyl fragments. The 3,4-dihydroxybenzoyl analogue was accessed via a similar route; the proton and carbon-13 NMR spectra of this compound were consistent with those reported for natural petrobactin.     

Photophysical characteristics and density functional theory calculations of indole 2-carboxylic acid in the presence of mercurous ions

Many photo-physical studies have been reported for the detection of Hg²⁺ ions. Here we present the effect of Hg ₂ ²⁺ ions on the absorption and fluorescence of indole-2-carboxylic acid (I2C). Experimental evidence, supported by density functional theory B3LYP/LANL2DZ/PCM, for the formation of a I2C-Hg ₂ ²⁺ complex, is reported for the first time. It was observed that I2C forms a ground-state complex with Hg ₂ ²⁺ ions in a ratio of 3:1. The possibility of I2C to be used as a selective novel chemical sensor for the spectrophotometric detection of mercurous ions is described.