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3-Aminopyrazole was utilized as a starting material for the preparation of certain pyrazolo-[1,5-a]-1,3,5-triazines. 4-Chloro-2-methylthiopyrazolo[1,5-a]-1,3,5-triazine was prepared and used for studies of nucleophilic displacement reactions, and it has been found that both the chloro and methylthio groups may be displaced by nucleophiles. By modifications of these procedures we have prepared the adenine, hypoxanthine, and xanthine analogs of the pyrazolo-[1,5-a]-1,3,5-triazine ring system. Electrophilic substitution occurs in the 8-position of this ring system. The methyl group was introduced into the 4-position by a novel ring opening and ring closing of the 1,3,5-triazine ring. 相似文献
4.
A core model approach to the calculation of deuteron quadrupole coupling constants is investigated using NH3 as an example. First the deuteron quadrupole coupling constant is calculated from a CNDO wave function. This result is subsequently improved by recomputing the N—D bond orbital by means of a variational calculation using the CNDO function to construct a core potential for the bond Hamiltonian. In order to simplify integrations a single-center basis is chosen to represent the variational wave function. A projection operator formalism is used as a computational scheme to maintain orthogonality of the bond orbital to core orbitals. Excellent agreement with experiment is obtained. The procedure is applicable to more complicated molecules. 相似文献
5.
A series of N-phenyl-3-methylthiopropylamine hydrochlorides were prepared by reacting a series of anilines with methional and sodium cyanoborohydride. These were cyclized upon oxidation by N-chloro-succinimide to the corresponding N-phenyl-S-methylisothiazolidinium derivatives which were isolated as the tetraphenylborate salts. Compounds successfully prepared included the m-methyl, p-methyl, m-methoxy, and p-methoxyphenyl derivatives. 相似文献
6.
The ligand, 1,2-bis(difluorophosphino)ethane, (PF2C2H4PF2), reacts with Ni(CO)4 in the gas phase and in solution to produce carbon monoxide and a polymer, [Ni(PF2C2H4PF2)2]x. PF2C2H4PF2 displaces norbornadiene from (C7H8)Mo(CO)4 to yield the relatively air-stable complex, Mo(CO)4-(PF2C2H4PF2). Analysis of the infrared spectrum of the monomeric complex indicates that the ligand exhibits π-acceptor strength equal to PF2C6H10PF2. 相似文献
7.
L. Ambrosone L. Costantino G. D’Errico V. Vitagliano 《Journal of solution chemistry》1997,26(7):735-748
The self-diffusion coefficients of HDO and some surfactants in aqueous mixtures at different concentrations, below the critical
micelle concentration, have been determined by means of the NMR, spin-echo pulsed field gradient method. The surfactant solutes
chosen were ethylene glycol-pentyl alcohol (diethylene glycolpentylalcohol, ethylene glycol-hexyalcohol, diethylene glycol-hexyl
alcohol, triethylene glycol-hexyl alcohol, tetraethylene glycol-hexyl alcohol, pentaethylene glycol-hexyl alcohol). The interactions
in solution are studied by analyzing the solute self-diffusion coefficients extrapolated to infinite dilution. These values
are compared with those of 1-alkanols. The slope of the self diffusion coefficientsvs. the solute concentration are correlated with the microscopic friction coefficients. A model for interpreting the experimental
data is suggested. 相似文献
8.
Pirrung MC Liu Y Deng L Halstead DK Li Z May JF Wedel M Austin DA Webster NJ 《Journal of the American Chemical Society》2005,127(13):4609-4624
The principle of methyl scanning is proposed for determination of the sites of interaction between biologically active small molecules and their macromolecular target(s). It involves the systematic preparation of a family of methylated derivatives of a compound and their biological testing. As a functional assay, the method can identify the regions of a molecule that are important (and unimportant) for biological activity against even unknown targets, and thus provides an excellent complement to structural biology. Methyl scanning was applied to demethylasterriquinone B1, a small-molecule mimetic of insulin. A new, optimal total synthesis of this natural product was developed that enables the family of methyl scan derivatives to be concisely prepared for evaluation in a cellular assay. The results of this experiment were used to design a biotin-demethylasterriquinone conjugate for use as an affinity reagent. This compound was prepared in tens of milligram quantities in a four-step synthesis. 相似文献
9.
Marzio Cassandro Enza Orlandi Errico Presutti 《Probability Theory and Related Fields》1993,96(1):57-96
Summary We consider a one dimensional Ising spin system with a ferromagnetic Kac potential J(|r|),J having compact support. We study the system in the limit, »0, below the Lebowitz-Penrose critical temperature, where there are two distinct thermodynamic phases with different magnetizations. We prove that the empirical spin average in blocks of size –1 (for any positive ) converges, as »0, to one of the two thermodynamic magnetizations, uniformly in the intervals of size –p
, for any given positivep1. We then show that the intervals where the magnetization is approximately constant have lengths of the order of exp(c
–1),c>0, and that, when normalized, they converge to independent variables with exponential distribution. We show this by proving large deviation estimates and applying the Ventsel and Friedlin methods to Gibbs random fields. Finally, if the temperature is low enough, we characterize the interface, namely the typical magnetization pattern in the region connecting the two phases.The research has been partially supported by CNR, GNFM, GNSM and by grant SC1CT91-0695 of the Commission of European Communities 相似文献
10.
Ghazali NF Patterson DA Livingston AG 《Chemical communications (Cambridge, England)》2004,(8):962-963
Organic solvent nanofiltration (OSN) was used to investigate the mechanism of chiral selectivity in diastereomeric salt formation of alpha-phenylethylamine with D-tartaric acid and di-p-toluoyl-D-tartaric acid as resolving agents; results indicate that for these systems chiral selectivity occurs only upon crystallisation and chiral interactions in solution were negligible. 相似文献