Establishing the synthetic origin of amphetamines by 2H NMR spectroscopy

Nine samples of N-acetyl-3,4-methylenedioxyamphetamine (N-acetyl-MDA), prepared according to the most common synthetic procedures, are submitted to (2)H NMR spectroscopy. The relative deuterium content at the various sites of the molecule is shown to depend on its synthetic history. The technique provides a chemical fingerprint of N-acetyl-MDAs and it can be used to trace back the precursor materials and the synthetic pathways employed in the preparation of the samples.     

Preparation of the Enantiomerically Enriched Isomers of the Odorous Cyclic Ethers Clarycet ®, Florol ®, and Rhubafuran ® by Enzymatic Catalysis

All the enantiomerically enriched stereoisomers of Clarycet ^® ( 1 ), Florol ^® ( 2 ), and Rhubafuran ^® ( 3 ) were prepared by biocatalysis routes. Their absolute configurations were established, and their olfactory properties were fully evaluated.     

Unusual nitration of substituted 7-amino-1,8-naphthyridine in the synthesis of compounds with antiplatelet activity

Several 1,8-naphthyridine derivatives have been diazotizated to obtain the corresponding hydroxy derivatives or mixture of hydroxy and hydroxy nitro derivatives. The respective amounts of hydroxy and hydroxy nitro derivatives depends on the nature of the substituents, on their position on the naphthyridine nucleus, on the amount of sodium nitrite and on the reaction temperature. A study of the electronic density of some molecules suggests a possible explanation of the effects induced by the nature of the substituents and of their position. Some of the compounds were tested for their ability to inhibit human platelet aggregation in vitro induced by arachidonic acid. Only compound 26 showed interesting antiplatelet activity.     

Testing equality in lisp-like environments

A function is presented to test equality between lists. In any case the function requires at most one single traversal of the lists and behaves as follows:

1. if there are no cycles, it works as standardEQU AL functions;
2. if there are cycles, it does not give information about equality, but it can detect cycles, i.e. it signals which lists are cyclic.

A simplified version of the function is also considered which is always at least as efficient as standardEQU AL; it grants protection against cycles without signaling them. A coroutine organized version of the function is shown.     

Unexpected formation of 1-diethylaminobutadiene in photosensitized oxidation of triethylamine induced by 2,3-dihydro-oxoisoaporphine dyes. A 1H NMR and isotopic exchange study

[reaction: see text] Photoreduction of oxoisoaporphine dyes occurs via a stepwise mechanism of electron-proton-electron transfer that leads to the N-hydrogen oxoisoaporphine anion. When triethylamine, TEA, was used as the electron donor in anaerobic conditions, 1-diethylaminobutadiene, DEAB, was one of the oxidation products of TEA, among diethylamine and acetaldehyde. DEAB was identified by (1)H NMR and GC-MS experiments by comparison with the authentic 1-diethylaminobutadiene. This is the first report of a butadienyl derivative formed in the dye-sensitized photooxidation of TEA. In addition, isotopic exchange experiments with TEA-d(15) and D(2)O show that the hydrogens at carbon-2 and carbon-4 of the butadienyl moiety are exchangeable. The observed isotopic exchange pattern could be explained by the head-to-tail coupling of an N,N-diethylvinylamine intermediate that exchanges hydrogens at the C-beta via the enammonium ion.     

An iterative extended Hückel calculation for some amino acids containing sulphur and selenium

Semiempirical iterative extended Hückel calculations are performed for the dipolar ions of cystine, cysteine, methionine and their selenium analogues. An attempt has been made to interprete the wave function of cysteine in terms of localized molecular orbitals.

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Zusammenfassung Semiempirische iterative Rechnungen wurden nach der erweiterten Hückeltheorie für die dipolaren Ionen Cystin, Cystein, Methionin und ihre Selen-Homologen durchgeführt. Für den Fall des Cysteins wurde die Wellenfunktion auf lokalisierte Orbitale transformiert.

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Résumé On a analisé les ions dipolaires de la cystine, cystéine, methionine et leurs analogues séléniates avec la méthode semiempirique de Hückel étendue itérative. On a cherché à intérpreter la fonction d'onde pour la cystéine dans le schème des orbitales moleculaires localisées.

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Work performed with the financial support of the Consiglio Nazionale delle Ricerche.     

Predictive models to describe VLE in ternary mixtures water + ethanol + congener for wine distillation

The modeling of liquid–vapor equilibrium in ternary mixtures that include substances found in alcoholic distillation processes of wine and musts is analyzed. In particular, vapor–liquid equilibrium in ternary mixtures containing water + ethanol + cogener has been modeled using parameters obtained from binary mixture data only. The congeners are substances that although present in very low concentrations, of the order of part per million, 10⁻⁶ to 10⁻⁴ mg/L, are important enological parameters [1] and [2]. In this work two predictive models, the PSRK equation of state and the UNIFAC liquid phase model and two semipredictive activity coefficient models: NRTL and UNIQUAC have been used. The results given by these different models have been compared with literature data and conclusions about the accuracy of the models studied are drawn, recommending the best models for correlating and predicting the phase equilibrium in this type of mixtures.     

V2O5/TiO2 Catalytic Xerogels Raman and EPR Studies

Raman spectroscopy and Electron Paramagnetic Resonance (EPR) studies were performed on a series of V₂O₅/TiO₂ catalysts prepared by a modified sol-gel method in order to identify the vanadium species. Two species of surface vanadium were identified by Raman measurements, monomeric vanadyls and polymeric vanadates. Monomeric vanadyls are characterized by a narrow Raman band at 1030 cm^–1 and polymeric vanadates by two broad bands in the region from 900 to 960 cm^–1 and 770 to 850 cm^–1. The Raman spectra do not exhibit characteristic peaks of crystalline V₂O₅. These results are in agreement with those of X-ray Diffractometry (XRD) and Fourier Transform Infrared (FT-IR) previously reported (C.B. Rodella et al., J. Sol-Gel Sci. Techn., submitted). At least three families of V⁴⁺ ions were identified by EPR investigations. The analysis of the EPR spectra suggests that isolated V⁴⁺ ions are located in sites with octahedral symmetry substituting for Ti⁴⁺ ions in the rutile structure. Magnetically interacting V⁴⁺ ions are also present as pairs or clusters giving rise to a broad and structureless EPR line. At higher concentration of V₂O₅, a partial oxidation of V⁴⁺ to V⁵⁺ is apparent from the EPR results.     

Theoretical study of the electronic spectrum of binuclear gold(I) complexes

The electronic structure and the spectroscopic properties of [Au₂(CS₃)₂]^?2, [Au₂(pym‐2‐S)₂] (pym = pyrimidethiolate), [Au₂(dpm)₂]⁺² (dpm = bis(diphosphino)methane) were studied using density functional theory (DFT) at the B3LYP level. The absorption spectrum of these binuclear gold(I) complexes was calculated by single excitation time‐dependent (TD) method. All complexes showed a ¹(5dσ* → 6pσ) transition associated with a metal–metal charge transfer, which is strongly interrelated with the gold–gold distance. Furthermore, we have calculated the frequency of the gold–gold vibration (ν_Au2) on the above complexes. The values obtained are theoretically in agreement with experimental range. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005     

FLUORESCENCE QUANTUM YIELDS OF 124-kDa PHYTOCHROME FROM OAT UPON EXCITATION WITHIN DIFFERENT ABSORPTION BANDS

Abstract— A fluorescence quantum yield (emission at650–850 nm) of π= (2.3 ± 0.3)10⁻³ was measured for the red-absorbing form (Pr) of 124-kDa phytochrome from etiolated oat seedlings ( Avena sativa ) upon excitation in the Soret band at Λ^exc= 380 nm. The small difference between this value and the previously determined quantum yield with Λ^exc= 640 nm, π= (3.5 ± 0.4)10⁻³is attributed to a blue-absorbing emitter responsible for the "anomalous" or "blue" emission of the chromoprotein in the region from ca. 400 to 550 nm. The absorption of Pr at 380 nm is consequently somewhat lower than that measured directly from the spectrum. Processes from upper excited states of the Pr phytochromobilin-derived chromophore other than rapid relaxation to the emitting state are not important. A quantum yield of Φ ' 1.2 times 10⁻³ is estimated for the blue fluorescence. The proportion of the blue emitters relative to Pr appears to be relatively high.