N-acyl glycinates as acyl donors in serine protease-catalyzed kinetic resolution of amines. Improvement of selectivity and reaction rate

Enzymatic kinetic resolution of aliphatic and benzylic amines leading to (S)-amides was achieved by using alkaline protease as the catalyst and N-octanoyl glycine trifluoroethyl ester as the acyl donor; enantioselectivity ranged between 4 to 244, while reaction times were dramatically shortened and ranged between 15 min to 6 h.     

Synthesis of DEFG ring of complestatin and chloropeptin I: highly atropdiastereoselective macrocyclization by intramolecular Suzuki-Miyaura reaction

Palladium-catalyzed intramolecular Suzuki-Miyaura reaction of linear tripeptide (23) afforded the 16-membered DEFG ring of complestatin (3) in good yield with an excellent atropdiastereoselectivity. Acidic treatment of 3 triggers a stereospecific rearrangement leading to the corresponding DEFG ring 4 of chloropeptin I.     

Lithium-cation/pi complexes of aromatic systems. The effect of increasing the number of fused rings

The gas-phase lithium cation basicities (LCBs) of naphthalene, azulene, anthracene, and phenanthrene were measured by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The structures of the corresponding complexes and their relative stabilities were investigated at the B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d) level of theory. In the theoretical survey, pyrene, coronene, [3]phenylene, angular [3]phenylene, and circumcoronene were also included. The strength of the binding to a given aromatic cycle decreases as the number of cycles directly fused to it increases. Hence, the stability of the outer pi-complexes, in which Li(+) is attached to the peripheral rings, is systematically greater than that of the complexes in which the metal is attached to the inner rings. The energy gap between these local minima decreases as the number of fused rings in the system increases. This result seems to indicate that, as the size of the system increases, the rings tend to lose their peculiarities, in such a way that in the limit of a graphite sheet all rings would exhibit identical characteristics and reactivity. The good agreement between calculated LCBs and experimental values lends support to the enhanced stability of the outer complexes. The activation barriers connecting these local minima decrease as the number of fused cycles increases, but seems to tend toward a limit. [3]Phenylene and angular [3]phenylene exhibit enhanced LCBs reflecting nonnegligible Mills-Nixon effects that increase the electron-donor properties of these annelated benzenes.     

Iron(II)/copper(I)-mediated stereoselective carbozincation of ynamides. One-pot synthesis of α-allyl-tetrasubstituted-enamides

The iron(II) chloride- and copper(I) iodide-mediated carbozincation of a panel of substituted ynamides is described in this article. The reaction is totally regio- and stereoselective. Experiments showed that the reaction mediated with Fe(II) was more substrate dependent than the reaction performed with Cu(I). Interestingly, in the presence of allylbromide, stereoselective carboallylation can be achieved for the first time in a one-pot procedure, leading to skipped dienamides.     

Crystallization kinetics of yttrium aluminate glasses

Journal of Thermal Analysis and Calorimetry - Yttrium aluminate glasses with eutectic AY-E and near-eutectic composition AY-NE were prepared in the form of glass microspheres. Their basic...     

Dependence of the Average Size of Particles Formed during Steady Mixing on their Concentration in Immiscible Polymer Blends

A linear increase in the size of ethylene-propylene rubber particles with its content in polypropylene matrix at steady mixing in a batch mixer was observed. This type of the dependence is predicted by the theory of dynamic equilibrium between the droplet breakup and coalescence. However, theoretical calculation of droplet radius extrapolated to zero concentration of EPR and slope of the dependence of droplet radius versus concentration, based on the effective shear rate (related to mixing conditions), are in strong disagreement with the experimental results. Reasons for these discrepancies between theories and experimental results are thoroughly elucidated.     

[(C C)Au(N N)]+ Complexes as a New Family of Anticancer Candidates: Synthesis,Characterization and Exploration of the Antiproliferative Properties

A library of eleven cationic gold(III) complexes of the general formula [(C C)Au(N N)]⁺ when C C is either biphenyl or 4,4’-ditertbutyldiphenyl and N N is a bipyridine, phenanthroline or dipyridylamine derivative have been synthesized and characterized. Contrasting effects on the viability of the triple negative breast cancer cells MDA-MB-231 was observed from a preliminary screening. The antiproliferative activity of the seven most active complexes were further assayed on a larger panel of human cancer cells as well as on non-cancerous cells for comparison. Two complexes stood out for being either highly active or highly selective. Eventually, reactivity studies with biologically meaningful amino acids, glutathione, higher order DNA structures and thioredoxin reductase (TrxR) revealed a markedly different behavior from that of the well-known coordinatively isomeric [(C N C)Au(NHC)]⁺ structure. This makes the [(C C)Au(N N)]⁺ complexes a new class of organogold compounds with an original mode of action.