Traceless solid-phase synthesis of 2,4,6-chlorodiamino and triaminopyrimidines

An effective traceless solid-phase synthesis of chloro-diaminopyrimidines via an amino-de-chlorination reaction of polymer-bound 4-alkoxycarbonylamino-2,6-dichloropyrimidines has been developed. After release from the polymer the target molecules were obtained in good to excellent purity, although with modest regiocontrol. Further reaction of solid-supported N-alkoxycarbonyl-chloro-diaminopyrimidines with secondary amines afforded triaminopyrimidines in good purity under mild conditions, whereas less nucleophilic primary amines did not perform well under the conditions explored so far.     

Quantum molecular study of sulfur mustard

The sulfur mustard, HD, a chemical warfare agent, has been studied by ab initio quantum molecular computations (HF /6-31G * and 6-31G ) on its various forms (neutral, ethylene sulfonium, and free carbonium ions). The geometries of these molecules have been completely optimized and the minimal energy conformations determined with their associated charge distributions. We discuss these results on electrostatic properties with respect to the mechanism of DNA alkylation by HD and compare them with our previous study of the nitrogen mustard mechlorethamine.     

The influence of ionic strength on the interaction of viruses with charged surfaces under environmental conditions

The influence of ionic strength on the electrostatic interaction of viruses with environmentally relevant surfaces was determined for three viruses, MS2, Q beta, and Norwalk. The virus is modeled as a particle comprised of ionizable amino acid residues in a shell surrounding a spherical RNA core of negative charge, these charges being compensated for by a Coulomb screening due to intercalated ions. A second model of the virus involving surface charges only is included for comparison. Surface potential calculations for each of the viruses show excellent agreement with electrophoretic mobility and zeta potential measurements as a function of pH. The environmental surface is modeled as a homogeneous plane held at constant potential with and without a finite region (patch) of opposite potential. The results indicate that the electrostatic interaction between the virus and the oppositely charged patch is significantly influenced by the conditions of ionic strength, pH and size of the patch. Specifically, at pH 7, the Norwalk virus interacts more strongly with the patch than MS2 (approximately 51 vs approximately 9kT) but at pH 5, the Norwalk-surface interaction is negligible while that of MS2 is approximately 5.9kT. The resulting ramifications for the use of MS2 as a surrogate for Norwalk are discussed.     

Sur la composition de l'arôme de thé

A gas-chromatographic investigation of black tea aroma has revealed, besides 19 known components, the presence of 4 new substances: 1-penten-3-ol, trans-2-hexen-1-ol, α-terpineol and β-ionone. The fragmentation pattern of 1-penten-3-ol has been determined by means of high resolution mass spectrography.     

Thermodynamic statistical evaluation ofS andF from ESR experimental order parameters.

Summary A statistical analytical procedure for calculating entropy (S) and Helmholtz free energy (F) from the order parameters obtained from ESR spectra of spin-labelled membranes is described. The method is here applied to some literature data. A brief discussion on the results is also reported.

---

Riassunto Si descrive un metodo statistico per calcolare l'entropia (S) e l'energia libera di Helmholtz (F) dai parametri d'ordine ottenuti da spettri ESR di membrane spin-marcate. Il metodo è applicato da alcuni dati di letteratura e sono brevemente discussi i risultati ottenuti.

---

Резюме Описывается статистическая аналитическая процедура вычисления энтропии (S) и свободной энергии Гельмгольца (F) из параметров порядка , полученных из ESR спектров для мембран со спиновыми метками. Развитый мэтод применяется к некоторым данным, имеюшимися в литературе. Проводится обсуждение полученных результатов.

     

Sur la composition de l'arôme de thé noir II

Trans-2-penten-1-ol, 1-ethyl-2-formyl-pyrrole, 2-trans, 4-cis-heptadienal, phenyl-acetonitrile, methyl benzoate, 2-phenyl-but-2-enal and the lactone of 2,6,6-trimethyl-2-hydroxy-cyclohexylidene acetic acid have been separated from black tea aroma by gas-liquid chromatography, and identified by infra-red and mass spectrometry.