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101.
102.
Saverio Florio Filippo M. Perna Renzo Luisi José Barluenga 《Tetrahedron letters》2004,45(43):8027-8030
The synthesis of α-oxazolinylalkanamides 2, based on the reaction of α-chloroalkyloxazolines 1 with hexacarbonyltungsten [W(CO)6] and lithium amides, has been developed. A plausible mechanism involving the ketene 5 as the intermediate is also proposed. 相似文献
103.
Florio S Lorusso P Granito C Luisi R Troisi L 《The Journal of organic chemistry》2004,69(15):4961-4965
The vicarious nucleophilic substitution reaction of dichloromethyloxazoline 2 with nitrobenzene has been investigated. Treatment of 2 with t-BuOK followed by the addition of nitrobenzene leads to benzylic carbanions 4 or 9 depending upon the solvent used (DMSO, DMF, or THF). Subsequent treatment of 4 or 9 with aldehydes, in a Darzens-like reaction, furnishes very good yields of nitrophenyl oxazolinyloxiranes 8 and 11. 1,2-Dioxazolinyl-1,2-dinitrophenylethene 7 forms quantitatively when carbanion 4 is allowed to warm to room temperature in the absence of external electrophiles. 相似文献
104.
The first stereoselective synthesis of oxazolinyl[1,2]oxazetidines based on the reaction of lithiated 2-(1-chloroethyl)-2-oxazolines with nitrones is described. Highly enantioenriched oxazolinyl[1,2]oxazetidines have also been prepared starting from a 1:1 diastereomeric mixture of optically active 2-(1-chloroethyl)-2-oxazolines. 相似文献
105.
The chemical characterization of horse liver alcohol dehydrogenase solubilized in isooctane via reverse micelles formed by the anionic surfactant di (2-ethyl-hexyl) sodium sulfosuccinate (AOT) and water (0.6 to 4% v/v) is presented. The enzyme’s catalytic activity toward acetaldehyde reduction is markedly dependent upon w0 = [H2O]/[AOT], and upon the pH of the stock aqueous solution (pHst), from which the hydrocarbon enzyme solution is prepared. Kinetically, the micellar solution appears to follow a normal Michaelis-Menten behavior, with a turnover number which, under the optimal conditions (w0 = 42, pHst = 8.8), appears to be higher than in bulk water. The affinity between enzyme and NADH, as judged from direct binding studies (quenching of the protein fluorescence), is much reduced with respect to water if concentrations refer to the water pool of the micelles, and comparable to water if concentrations refer to the overall volume (hydrocarbon plus water pool). Also, the Km values are much higher if concentrations refer to the water pool. Ultraviolet absorption studies show that the aromatic chromophores are not significantly perturbed on going from a water solution to the micellar solution. The essentially aqueous environment of the protein in the reverse micelles is confirmed by fluoresence studies. Circular dichroism studies show that the enzyme’s conformation in the micelles is similar to that in water; however, under certain conditions, small but significant changes of the main chain folding seem to occur, which do not impair enzymatic activity. The spectroscopic properties of NADH in the hydrocarbon phase (fluorescence and circular dichroism) are also investigated. The potential of the LADH-NADH system for technical applications (oxidoreduction of lipophylic substrates) is discussed. 相似文献
106.
RNA and vesicles are two important molecular classes in the origin of life and early evolution, but they are not generally considered as interacting partners. The present paper reports about the interaction between tRNA (Esherichia coli) and vesicles made of the zwitterionic surfactant POPC (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine), partially positively charged with small molar fractions (max 10%) of the single-chained CTAB (cetyltrimethylammonium bromide). CTAB is capable to insert efficiently in POPC vesicles (as determined by zeta-potential measurements), and the binding of tRNA to such charged vesicles operates a strong selection being critically dependent upon the vesicle size. The binding of tRNA to the vesicles is size-selective as it induces a strongly pronounced process of aggregation of large vesicles (ca. 160-nm diameter) but not of small ones (ca. 80-nm diameter) that are stable against vesicle aggregation (as followed by dynamic light-scattering and optical density measurements). The aggregation of the large vesicles is fully reversible upon the addition of RNase A. The selective behavior of tRNA with respect to differently sized vesicles is observable in separated samples as well as in a mixture of both populations. In the latter case, the fraction of large vesicles readily aggregates in the presence of the small ones that remain unaltered in the mixture. This kind of discrimination capability of RNA might have been of importance in the early phases of the formation of the protocells. 相似文献
107.
DNA was studied in lipid reverse micelles with the aim of investigating the interactions of DNA with lipids in a restricted compartment with minimal water content. Circular dichroic (CD) spectra of DNA at low water content showed the characteristic polymer-salt-induced (psi) spectra of condensed DNA. Dynamic light scattering showed a peak around a radius of 400 nm (corresponding to DNA-containing micelles), and a peak around 2.5 nm (corresponding to "empty" micelles). Fourier Transform-IR (FT-IR) spectroscopy was carried out and analyzed in terms of three distinct states of water inside the micelle water pool, where the local concentration of DNA reached an estimated value of ca. 600 mg/mL, comparable to that found in restricted biological compartments. 相似文献
108.