The novel C2-symmetric chiral organocatalysts of (2S,4R)-hydroxyproline containing podand type have been synthesized and evaluated in the asymmetric Biginelli reaction. Combination of polyether spacer with (2S,4R)-hydroxyproline allowed one to enhance the effect of the latter on enantioselectivity of the Biginelli reaction by a factor of 5. The best results have been achieved for salts of (2S,4R)-hydroxyproline containing podands with trifluoroacetic acid.
The first synthesis of 3,5-dimethyl-1-boraadamantane from its easily available tetrahydrofuran adduct comprised sequential treatment with BuLi, AcCl, (Cy2BH)2 and heating. The compound was converted into its electronic ‘antagonist’, namely, 3,5-dimethyl-1-azaadamantane.
Boiling intensifies the radiolytic conversion of diglyme since it stimulates the cleavage of the C–O bonds in the excited molecules and the primary radical cations, enhances the radical exchange reactions, and weakens the diglyme regeneration reactions.
A convenient approach to novel symmetric bispyrimidine diamines comprises SNAr reactions of 4-fluoropyrimidine N-oxide with alkane-α,ω-diamines with subsequent reduction of N-oxide function. The obtained substances were tested in patch-clamp experiments for the influence on the kainateinduced currents in Purkinje neurons and showed negative modulating effect.相似文献
Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc*) and degree of ionization of micelles were obtained at a fixed -CD concentration (mCD). From the cmc* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given mCD, the apparent molar volume V,CD and heat capacity C,CD of -CD in the two surfactants were calculated as functions of surfactant concentration mS. For both NaDS and DTAB, V,CD increases with mS up to about the cmc beyond which it decreases to a constant value at high mS, the opposite is observed for C,CD. With NaDS, a jump in the C,CD vs, mS trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume VS and heat capacity CS of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume VS and heat capacity CS of transfer of the surfactant from water to water+-CD mixture as functions of mS were calculated. For both surfactants, the VS vs. mS trends increase to the cmc and then decrease in a monotonic manner, whereas CS increases regularly with mS in the pre-micellar region and is essentially constant in the post-micellar region. The VS vs. mS trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions. 相似文献
Summary The thermal degradation products of the 7- and 7-cholesteryl 3-acetate hydroperoxides obtained by thermal oxidation of cholesteryl 3-acetate are reported and discussed. The hydroperoxides were degraded in both the vapour and condensed phases. The main components identified were 7-ketocholesteryl 3-acetate, 7- and 7-hydroxycholesteryl 3-acetates and the products generated from the loss of the hydroperoxide group and/or of acetic acid. Remarkable is the finding of the epoxy-hydroxy derivatives of cholesteryl acetate among the degradation products. 相似文献
