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101.
Roccaldo Sardella Maura Marinozzi Federica Ianni Antonella Lisanti Benedetto Natalini 《Analytical and bioanalytical chemistry》2013,405(2-3):847-862
In the frame of a project aimed at finding non-steroidal farnesoid X receptor (FXR) agonists, we identified 4-(2,4-dimethoxyphenyl)-3,6-dimethyl-1-(2-tolyl)-4,8-dihydro-1H-pyrazole[3,4-e][1,4]thiazepin-7-one (1) as a hit endowed with FXR activity. Most of the compounds synthesised during the hit-to-lead optimisation work were characterised by the presence of two chiral centres and were therefore obtained as mixtures of anti(±)- and syn(±)-diastereoisomers. A restricted sub-set of species harboured with a carboxylic acid group on the distal phenyl ring of the biphenyl (a(±)5 (A1) and s(±)5 (S1)) or the phenoxyphenyl (a(±)6 (A2) and s(±)6 (S2)) moiety at C-4 position of the pyrazole[3,4-e][1,4]thiazepin-7-one core, resulted in suitable diastereo- and enantioresolution with a quinine (QN) carbamate-derived chiral stationary phase (CSP). Differently from the compounds usually analysed with QN-based CSPs, the couples A1/S1 and A2/S2 were atypical selectands, in which the two chiral carbon atoms reside at a remote position with respect to the carboxylic function, the main “point of attack” to the CSP. We produced evidence that the scarcely employed normal-phase (NP) eluent systems represent the elective choice for achieving the simultaneous diastereo- and enantioseparation of this class of compounds over the usually preferred reversed-phase (RP) and polar-organic (PO) modes of elution. Indeed, after the optimisation of the eluent composition, NP conditions allowed to obtain profitable enantioselectivity profiles, along with excellent diastereoselectivity levels (α(A1)?=?1.07, R S(A1)?=?1.15; α(S1)?=?1.09, R S(S1)?=?1.47; α(A2)?=?1.08, R S(A2)?=?1.31; and α(S2)?=?1.06, R S(S2)?=?1.18). The optimised NP methods are suitable for simultaneously providing information on the diastereo- and enantiopurity of the investigated compounds. Figure
Simultaneous diastereoand enantioseparation of two non-steroidal FXR agonists with a quinine carbamate-based chiral stationary phase, in the normal-phase mode of elution. 相似文献
102.
Roccaldo Sardella Antonella Lisanti Andrea Carotti Paolo Blasi Wolfgang Lindner Benedetto Natalini 《Journal of separation science》2014,37(19):2696-2703
With the present contribution, we demonstrate that the baseline separation of ketoprofen enantiomers can be successfully achieved (α = 1.09; RS = 1.60) in the reversed‐phase mode of elution with a commercially available anion‐exchange‐based chiral stationary phase, incorporating the quinine 2,6‐diisopropylphenyl carbamate derivative as the enantioresolving unit. Focused modification of the eluent composition indicated a stereoselective role of hydrophobic and π–π interactions between the selector and selectand units, besides the prime ionic intermolecular interaction. The mechanistic hypotheses based on the chromatographic data were confirmed by in silico molecular dynamic simulations, which allowed us to establish the network of selector–selectand interactions underlying the stereorecognition process at a molecular level. The validated method was successfully used to evaluate the drug content and release profile of ketoprofen‐loaded polymeric film, showing drug homogeneous distribution into the film and no preferential interactions between the polymer and one of the enantiomers, with the racemate released at each time point. 相似文献
103.
Benedetto D. Caglioti E. Carrillo J. A. Pulvirenti M. 《Journal of statistical physics》1998,91(5-6):979-990
We consider a nonlinear Fokker–Planck equation for a one-dimensional granular medium. This is a kinetic approximation of a system of nearly elastic particles in a thermal bath. We prove that homogeneous solutions tend asymptotically in time toward a unique non-Maxwellian stationary distribution. 相似文献
104.
Lorenzo Pellerito Alessandro Pellerito Francesco Maggio Mariano Beltramini Benedetto Salvato Fernanda Ricchelli 《应用有机金属化学》1993,7(2):79-84
Protoporphyrin IX (H4PPIX) complexes of diorganotin(IV)chloro moieties with formula (R2SnCl)2H2PPIX (R?Me, Bu and Ph) have been obtained and their solid-state and solution-phase configurations have been studied through spectroscopic investigations. Coordination of the side-chain carboxylates of H4PPIX to R2Sn(IV)Cl moieties, with bridging carboxylate (COO?) has been inferred by comparison of the free and coordinated H4PPIX IR spectra, while the occurrence of a five-coordinated tin(IV) atom in a cis-R2 trigonal bipyramidal structure has been deduced, for all of the synthesized complexes, by rationalization of the nuclear quadrupole splitting parameters, according to the point-charge model formalism. Fanally, the solution-phase spectral features of (R2SnCl)2?H2PPIX are in agreement with the monomeric character of the protoporphyrin IX, under the experimental conditions used. 相似文献
105.
G. Ajroldi G. Pezzin G. Astarita F. R. Schwarzl L. G. Napolitano E. Butta G. Marrucci U. Bianchi J. C. Halpin L. Nicolais M. Pegoraro E. Pedemonte P. L. Mazzucco L. Patron S. Eccher A. Seves A. Croce G. Manfré A. T. Di Benedetto R. Greco D. Acierno C. Rossi A. Perico G. P. Giuliani W. Conti E. Sorta C. Garbuglio L. Costantino G. Nardi V. Vitagliano L. Nicodemo L. Szilagyi A. C. Bassi U. Delle Piane F. de Candia G. Ballini S. Danesi A. Moroni A. Casale L. Corbelli 《Rheologica Acta》1972,11(1):133-142
106.
G. E. De Benedetto F. Catalano L. Sabbatini P. G. Zambonin 《Fresenius' Journal of Analytical Chemistry》1998,362(1):170-175
This paper is part of a systematic archaeometric investigation aimed at the characterisation of the pigments and related
materials (ligand, colour substrate) used in decoration of pottery excavated in the archaeological zone of Canosa (Puglia,
Italy). Shards found in thirteen different tombs have been analysed; in this paper samples exhibiting a white colouration
have been selected. Both surface (XPS) and bulk (FT-IR) spectroscopies were used which gave complementary information and
enabled white pigments to be divided into two groups. Moreover, X-ray diffraction was used in some cases to further support
some spectral assignments. The molecular specificity of FT-IR, when applied to the analysis of both pigments and ceramic body,
allowed the identification of the various constituents and, hence, provided indirect information on the end-use of the original
wares. The potential of the combined use of different spectroscopies to obtain valuable information on both painting materials
and technical aspects is shown.
Received: 5 December 1997 / Revised: 16 March 1998 / Accepted: 19 March 1998 相似文献
107.
108.
A chiral stationary phase based on tert-butylcarbamoyl quinine has shown remarkable enantiomer separation capability for the thyroid hormone thyroxine (T(4)) and its structural analogue triiodothyronine (T(3)) employing hydroorganic buffered mobile phases (typical RP conditions). To overcome the problem of a somehow limited chemoselectivity for the critical peak pair between adjacent L-thyroxine (L-T(4)) and D-thyroxine (D-T(4)) peaks on the chiral anion-exchanger CSP when all four compounds need to be analysed simultaneously like in impurity profiling of L-T(4 )drug products, an RP column (Gemini C18) was serially coupled with the chiral anion-exchanger column to add a hydrophobic selectivity increment and to improve thereby the critical resolution between L-T(3) and D-T(4). Various parameters such as organic modifier content, pH, buffer concentration and type, type of achiral column as well as sequence of achiral and chiral column have been investigated with individual and tandem columns. With the optimized conditions and use of the tandem column a significantly improved separation, as compared to the chiral anion-exchanger column alone, with a critical resolution as high as 3.7 and an almost equal band spacing of the four components of the test mixture could be obtained. The sequence of the columns (achiral-chiral or chiral-achiral) had no significant effect on the separation performance. 相似文献
109.
In this paper heat and mass transfer phenomena are studied in a catalytic monolith with a fast exothermic reaction taking place at the walls at fully developing laminar flow for different values of the kinetic parameters. A two-dimensional model has been adopted to simulate the behaviour of the monolith reactor. The unsteady Navier–Stokes equations have been discretized by adopting the control volume approach and solved by means of the CFD-ACE+ package. The model surface reaction is parametrically varied to account for the effects of the perturbation generated by heat production associated with the reaction on flow field, temperature and concentration profiles and then on transport. Results show that Nu and Sh trends are not monotonic functions but that there exists a transfer enhancement due to the perturbation of the flow field. This increase is shown to be dependent on the kinetics parameters of the surface reaction. We show that the definition of the new driving force we previously proposed, which relates the transfer coefficients to the adiabatic temperature rise, is also able to describe the effect of the kinetic parameters if the pre-exponential factor and the activation energy are included in the correlation. 相似文献
110.
Gioiello A Venturoni F Marinozzi M Natalini B Pellicciari R 《The Journal of organic chemistry》2011,76(18):7431-7437
Ethyl diazo(3-hydroxy-2-oxo-2,3-dihydro-1H-indol-3-yl)acetate was prepared by aldol-type condensation of ethyl diazoacetate with isatin. A systematic and mechanistic study on the Lewis acid induced decomposition reaction of this valuable diazo precursor was carried out with the aim to gain new insights into the mechanistic aspects of the reaction as well as to further understand the factors and experimental conditions which affect the relative product distribution. The reaction, which may proceed via cationic and noncationic mechanisms, was found to be significantly influenced by the reaction environment determined by the characteristics of the Lewis acid employed, by the ability of the Lewis acid to form a complex with the alcohol functionality of the α-diazo-β-hydroxy ester, and by the polarity and nucleophilicity of the solvent used. 相似文献