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101.
Graziano Baccolini Paolo E. Todesco Giuseppe Bartoli 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):387-393
Abstract The title reaction between substituted phenyl azides 2 and diastereomeric diazaphospholenes 1 gives the corresponding cyclic phosphazenes 3 with different stereochemical results. Hydrolysis of some phosphazenes 3 yield the corresponding ring-opened compounds Z-4I together with small amounts of diazaphospholene-oxide 5 and anilines 6. The configuration of the compounds obtained are established by 1H n.m.r. spectroscopy. The results are explained invoking the formation of pentacoordinate phosphorus intermediates. 相似文献
102.
Orazio Attanasi Paolo Battistoni Gabriele Fava 《Phosphorus, sulfur, and silicon and the related elements》2013,188(2):271-277
Abstract The rates of the base-catalyzed hydrogen-deuterium exchange at position 2, and the reverse, in some 5-and 6-substituted benzothiazoles are reported. The plots of log k sH, and log k sD against the [sgrave]m + [sgrave]p values of the substituents, according to the Hammett-Jaffé equations, are slightly curved. The primary hydrogen isotope effect k sH/k sD varies between 0.7 and 2.3 and the plot of log k sH/k sD against the [sgrave]m + [sgrave]p values of the substituents is a more pronounced curve, showing a maximum near to the [sgrave]m + [sgrave]p value of ?0.3. By these investigations the simple utilization of the primary hydrogen isotope effect in the prediction of reaction mechanisms seems extremely hazardous. 相似文献
103.
Paolo Marchini Giuseppe Trapani Gaetano Liso Vincenza Berardi 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):309-314
Abstract The title compounds (4b-d) together with the benzothiazolines (5b-d) have been obtained by a reaction between 2,2′-dithiodianiline (1) and β-keto esters (2b-d). The reaction between 1 and the β-keto ester 2a gives 1,4-benzothiazine 3a in addition to the benzothiazoline 5a. It has been established that the 1,4-benzothaizines 4b-d undergo an acid-catalysed thermal rearrangement involving a [1,3] shift of the sulfur atom, giving rise to the isomeric 1,4-benzothiazines 3b-d. 相似文献
104.
Abstract Three cases are described where chirality is recognized by achiral molecules, where chirality is induced into achiral compounds through interactions with chiral compounds, and lastly where induced chirality in the solid-state is utilized for an enantio-selective photoreaction. In the first instance, the thermodynamically and kinetically preferred diastereoisomer of an optically labile chromium complex depended on the nature of the achiral solvent. In the second case, for the first time 1,2-chloroethane was trapped and observed in a chiral near-eclipsed form and 1-chloropropane in the truly eclipsed form at room temperature in a 1:1 inclusion complex with an optically active host molecule. Finally, induced chirality in a prochiral compound in the solid-state was successfully employed in an enantio-selective photoreaction. In the two cases, solid-state CD provided valuable information. 相似文献
105.
Paolo Dapporto Paola Paoli Carla Bazzicalupi Andrea Bencini Nicoletta Nardi Barbara Valtancoli 《Supramolecular chemistry》2013,25(3):195-200
Abstract In preceding works, which have dealt with the synthesis and characterisation of a series of macrobicyclic compounds with five donor atoms, the unusually high basicity constants of these polyaminic cage-like molecules have been ascribed to the inclusion of the proton inside the macrobicyclic cavity which results in a very efficient hydrogen-bond network. The present paper, based on previously reported X-ray crystal structures regarding five-atoms bridging units and on molecular modelling studies shows that the disposition of the five donor atoms in the monoprotonated species is related to the protonation site. Precisely, if the protonation occurs on a bridge-head nitrogen the resulting geometry of the donors is a trigonal bipyramid, whereas it is square pyramidal when the proton is bound to a nitrogen belonging to a macrobicyclic chain. For what concerns the geometrical array of the donor atoms in the free amines, the favoured array seems to be the trigonal bipyramidal. 相似文献
106.
Peter C. Griffiths Nicolo Mauro Damien M. Murphy Emma Carter Simon C. W. Richardson Paul Dyer Paolo Ferruti 《Macromolecular bioscience》2013,13(5):641-649
A series of nanoparticles is prepared via layer‐by‐layer assembly of oppositely charged, synthetic biocompatible polyamidoamine polymers as potential carriers. Particle size, surface charge and internal chain mobility are quantified as a function of the polymer type and number of layers. The effect of addition of surfactant is examined to simulate the effects of nanoparticle dissolution. The cyctotoxicity of these particles (in epithelia and murine cell lines) are orders of magnitude lower than polyethyleneimine controls. Stable nanoparticles may be prepared from mixtures of strongly, oppositely charged polymers, but less successfully from weakly charged polymers, and, given their acceptable toxicity characteristics, such modularly designed constructs show promise for drug and gene delivery.
107.
A method for C-Br/C-H bis-phenylation of methyl 4-bromocrotonate via nickel-catalyzed cross-coupling reaction has been developed. This protocol involves commercially available catalyst components and furnishes a suitable doubly phenylated building block. 相似文献
108.
P. Sreejith Shankar Serena Bigotti Paolo Lazzari Ilaria Manca Marco Spiga Monica Sani Matteo Zanda 《Tetrahedron letters》2013
Tubulysins are potent anti-mitotic natural compounds and a scalable and efficient synthetic route for generation of its analogues has been developed and extended to the synthesis of diastereoisomers and N-terminal analogues of tubulysin-U. Structure–activity-relationship studies on these synthetic analogues reaffirmed the significance of native stereochemistry of tubulysins for optimal biological activity and cytotoxicity. However, while modification of Tup stereochemistry has only minor effect on the tubulysins cytotoxicity, Tuv stereochemistry is critically important and modification of either Tuv stereocentre produced a dramatic drop in cytotoxicity. 相似文献
109.
Dr. Alessandro Barge Marina Caporaso Prof. Giancarlo Cravotto Dr. Katia Martina Dr. Paolo Tosco Prof. Silvio Aime Dr. Carla Carrera Dr. Eliana Gianolio Dr. Giorgio Pariani Dr. Davide Corpillo 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(36):12086-12092
We report the synthesis and characterization of a water‐soluble, star‐shaped macromolecular platform consisting of eight β‐cyclodextrin (β‐CD) units anchored to the narrower rim of a γ‐CD core through bis(triazolyl)alkyl spacers. The efficient synthetic protocol is based on the microwave (MW)‐promoted Cu‐catalyzed 1,3‐dipolar cycloaddition of CD monoazides to CD monoacetylenes. The ligand‐hosting capability of the construct has been assessed by relaxometric titration and nuclear magnetic relaxation dispersion (NMRD) profiling, which showed it to be good, and this was supported by molecular dynamics simulations. To demonstrate the feasibility of obtaining supramolecular structures with high hosting ability, we designed a dimeric platform, formed by joining two nonamers through the γ‐CD cores through a bis(lithocholic acid) linker. With a view to the potential biological applications, cytotoxicity and extent of binding to human serum albumin were assessed. The properties of this dendrimeric multicarrier make it suitable for pharmaceutical and diagnostic purposes, ranging from targeted drug delivery to molecular imaging. 相似文献
110.
Olga Bortolini Dr. Alberto Cavazzini Pier Paolo Giovannini Roberto Greco Nicola Marchetti Dr. Alessandro Massi Luisa Pasti 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(24):7802-7808
The heterogeneous proline‐catalyzed aldol reaction was investigated under continuous‐flow conditions by means of a packed‐bed microreactor. Reaction‐progress kinetic analysis (RPKA) was used in combination with nonlinear chromatography for the interpretation, under synthetically relevant conditions, of important mechanistic aspects of the heterogeneous catalytic process at a molecular level. The information gathered by RPKA and nonlinear chromatography proved to be highly complementary and allowed for the assessment of optimal operating variables. In particular, the determination of the rate‐determining step was pivotal for optimizing the feed composition. On the other hand, the competitive product inhibition was responsible for the unexpected decrease in the reaction yield following an apparently obvious variation in the feed composition. The study was facilitated by a suitable 2D instrumental arrangement for simultaneous flow reaction and online flow‐injection analysis. 相似文献