Synthesis of 4-aryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b][1,4]-diazepin-6-ones from 4,5-diamino-1H-pyrimidin-6-ones and 1-aryl-3-(dimethylamino)-1-propanones

The reaction of 1-aryl-3-(dimethylamino)-1-propanones 1 with one equivalent of 4,5-diamino-1H-pyrimidin-6-ones 2 , in acidic medium, leads to the formation of 4-aryl-2,3,6,7-tetrahydro-1H-pyrimido[4,5-b]-[1,4]diazepin-6-ones 3 . The structure elucidation of the products is based on detail nmr analysis of experiments such as ¹³C, ¹H and DEPT including selective ¹³C{¹H} decoupling experiments.     

Enzymatic desymmetrization of a meso polyol corresponding to the C(19)-C(27) segment of rifamycin S

The stereoselective acylation of meso polyol 2 by vinyl acetate (solvent and acyl donor) in the presence of porcine pancreas lipase gave the corresponding monoester 5 in good yield (76%) and high enantiomeric purity (ee > 98%). The enzymatic reaction was also highly regioselective for a primary alcohol end group, and the two unprotected secondary alcohols were not involved. Compound 5 corresponds to the C(19)-C(27) fragment of rifamycin S.     

Un nouveau type d'alcaloïdes isoquinoleiques,les bisaporphines

The structures of Beccapoline and Beccapolinium, two new isoquinoline alkaloids from $\text{Polyathia beccarii}$, Annonaceae, have been elucidated by spectroscopic analysis. They are the first examples of natural bisaporphines.     

The complete symmetrization of quantum operators: new thoughts on an old problem

The complete symmetrization with respect to x, p _x,... of the operators associated with dynamical properties can sometimes lead to results different from those obtained by the conventional quantum formalism based on the rule op (A ²)=(op A)². For example, angular momentum operators M _z ² and M ² are modified by the additive constants ²/2 and 3 ²/2 respectively (M ²0 for electron in the ground state of H atom, rotator never at rest, but spectra unchanged); the average quadratic dispersion of energy is different from zero. These results can be interpreted by assuming that the system is never strictly isolated but communicates with the other systems of the universe by means of electromagnetic interactions. Quantum mechanics would give only average values over a sufficiently long time and would exhibit a quasi-ergodic character. Examples supporting this possibility are given, in particular that of arsines for which quantum forecasts correspond to average values over one year.Dedicated to Professor J. Koutecký on the occasion of his 65th birthday     

High-performance liquid chromatographic determination of cocaine and benzoylecgonine by direct injection of human blood plasma sample into an alkyl-diol-silica (ADS) precolumn

A column-switching high-performance liquid chromatographic method with UV detection for the determination of cocaine (COC) and benzoylecgonine (BZE) in human blood plasma samples is described. The method uses an alkyl-diol-silica ADS-C18 extraction precolumn. A 50- micro L plasma sample was introduced to the ADS precolumn in order to separate the analytes from proteins and endogenous compounds. The fraction containing COC and BZE was back-flushed and transferred to an Alltech mixed-mode C(18)/cation-exchange analytical column for final separation. The validation of the method revealed quantitative recoveries from 95.0 to 99.0% for COC at three different concentrations (0.5, 1.0 and 2.0 micro g mL(-1)), and from 96.0 to 99.0% for BZE at the same concentration levels with coefficients of variation <4.00% (n=5). The detection limit (signal to noise ratio (S/N)>3) was 0.03 micro g mL(-1) for all the compounds with an injection volume of 50 micro L. However, it was possible to enhance the sensitivity further by injecting larger plasma volumes, up to 200 micro L, at the same optimal conditions. The overlap of sample preparation, analysis and reconditioning of the extraction column, increase the overall sample throughput to 5 samples h(-1). The developed method has been applied to human blood plasma samples from subjects suspected of cocaine abuse.     

Fungicidal properties of meso-arylglycosylporphyrins: influence of sugar substituents on photoinduced damage in the yeast Saccharomyces cerevisiae

A series of neutral meso-arylglycosylporphyrins has been tested in order to evaluate their potency as antifungal agents against the yeast Saccharomyces cerevisiae. Photodynamic activity of these molecules results in intracellular damage as evidenced by the loss of clonogenicity and DNA fragmentation. The ability of these photosensitizers to permeate yeast cells is determined by microspectrofluorimetry and is correlated with their antifungal potency. Amphiphilic porphyrin derivatives are shown to exhibit the more pronounced photoactivity.     

Flash photolysis studies of the reaction of NH2 radicals with NO

The kinetics of the reaction NH₂ + NO → N₂ + H₂O were studied, using a conventional flash photolysis system. A value of k₁ = (1.1 ± 0.2) × 10¹⁰ & mole^?1 s^?1 was obtained at room temperature and in the pressure range 2–700 torr in the presence of nitrogen. A slight negative temperature coefficient was observed between 300 and 500 K, equivalent to a negative activation energy of 1.05 ± 0.2 kcal mole^?1.     

Enantiospecific synthesis of the (9S,18R)-diastereomer of the leukocyte adhesion inhibitor cyclamenol A

Cyclamenol A is one of the very few non-carbohydrate and non-peptide natural products that inhibit leukocyte adhesion to endothelial cells. We report on the first enantioselective total synthesis of the (9S, 18R)-diastereomer of this macrocyclic polyene lactam. Key elements of the synthesis are i) the synthesis of the required chiral building blocks by employing readily accessible building blocks from the chiral pool, that is, (S)-malic acid and (R)-hydroxyisobutyric acid, ii) assembly of a linear polyene precursor by means of Wittig and Horner olefination reactions as key C-C bond-forming transformations, iii) ring closure by means of a vanadium-mediated pinacolisation reaction and iv) conversion of the generated cis-diol into a (Z)-olefin to complete the entire polyene system of the natural product. Attempts to close the macrocyclic ring by a macrolactamisation, a double Stille coupling or direct olefination in a McMurry reaction failed. Crucial to the successful completion of the synthesis was the correct orchestration of the final steps. It was necessary to first deprotect the intermediate formed after macrocycle formation and to generate the sensitive heptaene system in the last step by means of a Corey-Hopkins sequence.     

Synthesis and X-ray crystal structure determination of first examples of donor-functionalized terphenyl lanthanide complexes

The molecular structures of novel donor-functionalized terphenyl derivatives of trivalent ytterbium, yttrium, and samarium of composition [DanipYb(mu2-Cl)2(mu3-Cl)Li(THF)]2 (1) and [DanipLn(mu2-Cl)2(mu2-Cl)Li(THF)2]2 (Ln = Y, 2; Ln = Sm, 3) are reported [Danip = 2,6-di(o-anisol)phenyl]. The complexes are obtained from the reaction of equimolar amounts of DanipLi and LnCl3 (Ln = Yb, Y, Sm) in tetrahydrofuran at room temperature in 60% yield. 1-2 toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 1-2 toluene at 203 K: a = 9.7281(9) A; b = 12.7989(12) A; c = 13.4870(12) A; alpha = 91.553(2) degrees; beta = 103.957(2) degrees; gamma = 109.916(2) degrees; V = 1521.2(2) A(3); Z' = 1; D(calcd) = 1.615 g cm(-3); R1 = 3.43%. 2-toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 2-toluene at 203 K: a = 10.4152(10) A; b = 12.5783(12) A; c = 14.4640(14) A; alpha = 69.963(2) degrees; beta = 80.900(2) degrees; gamma = 66.603(2) degrees; V = 1633.3(3) A(3); Z' = 1; D(calcd) = 1.386 g cm(-3); R1 = 4.07%. 3-toluene crystallizes in the monoclinic space group Ponebar. Crystal data for 3-toluene at 203 K: a = 10.3457(8) A; b = 12.5658(10) A; c = 14.4365(11) A; alpha = 70.2250(10) degrees; beta = 81.2820(10) degrees; gamma = 66.8330(10) degrees; V = 1623.3(2) A(3); Z' = 1; D(calcd) = 1.521 g cm(-3); R1 = 3.40%. Complexes 1-3 represent first examples of donor-functionalized terphenyl complexes of the elements ytterbium, yttrium, and samarium, respectively. The molecular structures of 1-3 feature a "constraint geometry" type arrangement of the Danip ligand at the lanthanide atom. The complexes reported are dimeric and composed of lithium chloride bridged DanipLnCl(2) moieties (Ln = Yb, Y, Sm), stabilized through additional coordination of two methoxy functions to the lanthanide atom.     

Influence of reduction conditions on H2 adsorption in high-surface Rh/CeO2 catalysts as deduced by volumetry, calorimetry, and 1H NMR techniques

1H NMR spectra corresponding to H2 adsorption on high-surface Rh/CeO2 catalysts (S(BET) approximately 55 m2/g) are formed by two lines, attributed to hydrogen adsorbed on ceria (resonance line A) and rhodium-metal particles (upfield-shifted line B). The evolution of 1H NMR spectra as a function of temperature, time, and type of reduction (static or dynamic) allows the study of the progressive establishment of the strong metal-support interaction (SMSI) in Rh/CeO2 catalysts. As the reduction progresses, the mean adsorption heat and the amount of hydrogen adsorbed on the metal, deduced from volumetry, NMR, and calorimetry techniques, decrease considerably. As a consequence of the decrease in metal activity, the amount of hydrogen transferred to the support CeO2 is also reduced (spill-over processes). Outgassing of samples at 773 K eliminates hydrogen species retained at the metal-support surface, and oxidation treatments at 473 and 673 K eliminate the electronic effect and physical blocking of metal particles. The oxidation at 673 K recuperates the total adsorption capacity of metal particles. On the basis of these treatments, the contribution of different processes to the SMSI effect is analyzed. Electronic perturbation of rhodium particles is higher when reductions are performed in dynamic conditions; however, the importance of physical blocking of metal particles increases in static reductions. High reducibility of ceria strengthens electronic effects in Rh/CeO2 compared to those observed in Rh/TiO2 catalysts.