Gas chromatographic separation and mass spectrometric identification of mixtures of oxyphytosterol and oxycholesterol derivatives application to a phytosterol-enriched food

Pure individual phytosterols were prepared using reversed-phase HPLC in order to obtain the oxidized compounds of sitosterol, campesterol, stigmasterol and brassicasterol. 7-Hydroxy-, 7-keto-, 5,6-epoxy-, 4beta-hydroxy-, 4-ene-6-hydroxy-, 6-keto- and 5alpha,6beta-dihydroxyphytosterols were obtained as well as analogous compounds of cholesterol. The gas chromatographic properties as well as the electronic impact mass spectra of these compounds (as trimethylsilyl ether derivatives) were studied. These data were used to identify oxyphytosterols in a spread enriched in phytosterols: the oxyphytosterols represented no more than 68 microg/g of spread (about 0.08% of phytosterols were oxidised).     

Theoretical study of pyridine and 4,4'-bipyridine adsorption on the lewis acid sites of alumina surfaces based on ab initio and density functional cluster calculations

The interactions of pyridine and 4,4'-bipyridine with the Lewis acid sites of alumina surfaces are investigated using ab initio and density functional calculations. Four cluster models of different sizes and shapes are chosen to represent the Lewis acid sites: three hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12) and one non-hydrogenated cluster Al(4)O(6). The Hartree-Fock (HF) and B3LYP approaches with two basis sets 6-31G and 6-31+G are used to calculate the geometries, the electronic structures, the vibrational frequencies, and the adsorption energies of the complexes formed upon interaction of pyridine or 4,4'-bipyridine ligands on the cluster surfaces. Electronic structures are determined by the electrostatic potential (ESP) analysis of charges. Adsorption energies are calculated with corrections made for zero-point energies (ZPE) and basis set superposition error (BSSE). The ESP analysis of atomic charges reveals that the charge-transfer effects are more important in Lewis complexes formed with Al(4)O(6) cluster than in those formed with hydrogenated clusters Al(OH)(3), Al(4)O(9)H(6), and Al(10)O(21)H(12). The significantly larger charge transferred from pyridine or 4,4'-bipyridine ligand to Al(4)O(6) cluster should increase the adsorption energy of these complexes. Consequently, at all levels of calculation, the adsorption energies of pyridine and 4,4'-bipyridine complexed to Al(4)O(6) cluster ( approximately 46 kcal/mol), which compare very well to experiment, are strongly larger than those obtained for both pyridine and 4,4'-bipyridine ligands complexed to Al(OH)(3) (32 kcal/mol), Al(4)O(9)H(6) (24 kcal/mol) and Al(10)O(21)H(12) (25 kcal/mol) clusters. The corrected adsorption energy is found to be insensitive to basis set and electron correlation effects. It essentially depends on the ionic character of the cluster model rather than on its size. For 4,4'-bipyridine complexes, similar results to those obtained for pyridine are found, and the geometry and the amount of charge of the unbound pyridyl ring are unchanged upon complexation. The calculated vibrational frequencies and frequency shifts are little sensitive to the size and shape of the cluster model. The two ring stretching modes 8a and 19b of pyridine and 4,4'-bipyridine observed in the 1400-1600 cm(-1) region are the most affected modes upon adsorption, in good agreement with the available infrared and Raman data.     

An inclusion complex between acetonitrile andp-tert-butylcalix[6]arene

p-tert-Butylcalix[6]arene forms a complex with 1.5 acetonitrile molecules, that are included in the macrocycle cavity. This complex crystallizes in the monoclinic system: space groupP2₁/m,a=14.043(4),b=16.916(11),c=14.199(11) Å,=98.27(6)°,V=3338(4) ų,Z=2 (formula units). Refinement led to a final conventionalR value of 0.113 for 1654 reflections. Thepinched cone conformation of the calixarene is the same as that of the neutral and freeR-calix[6]arene already described. The two acetonitrile molecules interact with some phenyl ring -clouds, a methylene bridge and sometert-butyl groups of the calixarene. Supplementary Data relating to this article (atomic coordinates for hydrogen atoms, anisotropic displacement parameters, selected geometrical parameters and observed and calculated structure factors) are deposited with the British Library as Supplementary Publication No. SUP 82188 (16 pages).     

Substitution directe de l'azote N-9 de la théophylline

In alkaline medium, 8-(2-chloroethyl)aminotheophylline (1) cyclizes into two imidazopurines: the imidazo[1,2-e]purine (2A) (cyclization on 9-N) and the imidazo[2,1-f]purine (2B) (cyclization on 7-N). The structure of each compound was determined by an unambiguous synthesis and confirmed by spectrographic methods. Synthesis of one pyrrlo[2,1-f]purine, a novel heterocycle, is described.     

Lithiation of functionalized fluoroquinolines: synthesis of dihalo-2-phenylquinoline-4-carboxamides and in vitro evaluation as NK-3 receptor ligands for medical imaging studies

Fluoroiodo-2-phenylquinoline-4-carboxamides, analogues of NK-3 antagonist SB 223412, were synthesized and evaluated as NK-3 ligands with the aim of developing radioligands suitable for both Positron Emission Tomography (PET) and Single Photon Emission Computed Tomography (SPECT) studies. The key step utilizes metalation directed by the fluorine atom for iodination of the quinoline ring.     

X- and Q-band EPR studies of the dinuclear Mn(II) complex [(Bpmp)Mn2(mu-OAc)2]+. Determination of the spin parameters for the S = 1 and S = 2 spin states

A new mu-phenoxo-bis-mu-acetato di-Mn(II) complex using the BpmpH ligand was isolated as a perchlorate salt (BpmpH = 2,6-bis[bis(2-pyridylmethyl)aminomethyl]-4-methyl-phenol). The X-ray structure has been solved showing that the two Mn(II) ions are in a distorted octahedral environment. Investigation of the variation of the molar magnetic susceptibility upon temperature reveals an antiferromagnetic exchange interaction between the two high-spin Mn(II) ions. Fitting of the experimental data led to g = 1.99 and J = 9.6 cm(-1) (H(HDvV) = JS(A).S(B)). EPR spectra recorded on a powder sample of [(Bpmp)Mn(2)(mu-OAc)(2)](ClO(4)).0.5H(2)O at X-band between 4.3 K and room temperature and at Q-band between 5 and 298 K are presented. A new method based on a scrupulous examination of the variation upon temperature of these experimental spectra is developed here to first assign the transitions to the relevant spin states and second to determine the associated spin parameters. This approach is compared to the deconvolution process that has been previously applied to dinuclear Mn(II) complexes or metalloenzyme active sites. Crystallographic data is as follows: triclinic, space group P one macro, a = 10.154(2) A, b = 12.0454(2) A, c = 17.743(4) A, alpha = 101.69(3) degrees, beta = 93.62(3) degrees, gamma = 94.67(3) degrees, Z = 2.     

Synthesis and Structure of a Bis-calix[4]arene with an o-Xylene Linkage

The reaction of p-tert-butyl calix[4]arene 1 with,'-dibromo-o-xylene in basic conditions leads totwo new compounds. One of them is a bis-calix[4]arene, whose crystal structure has been determined.     

Crystal Structure of a p-Benzylcalix[5]arene- pyridine Complex

p-Benzylcalix[5]arene.3py (py = pyridine) (1) crystallizes in the triclinic space group P1, a = 10.641(3), b = 13.975(3), c = 24.052(12) Å, = 94.60(4), = 91.51(4), = 111.46(2)°, V = 3312(4) ų, Z = 2. Refinement led to a final conventional R value of 0.065 for 5457 reflections. The calixarene is in a distorted cone conformation. Two pyridine molecules are hydrogen bonded to phenolic oxygen atoms and one of them is included in the hydrophobic cavity of the neighboring calixarene molecule along the a axis.     

Sensitive assay for nicotinamide adenine dinucleotide phosphate and its reduced form based on the bioluminescence method

An assay of reduced nicotinamide adenine dinucleotide phosphate (NADPH) by bioluminescence was investigated and applied for NADP⁺. The NADP⁺ is first reduced by glucose-6-phosphate dehydrogenase and then assayed in a mixture containing a NADPH/flavin mononucleotide oxidoreductase which in turn activates luciferase. Many interferences were observed and the method was modified accordingly. NADP⁺ and NADPH can be assayed separately or simultaneously within the range 1–100 pmol, which is sufficiently sensitive to be applied to biological materials. Many details and precautions must be taken into consideration.