Hemiasterlin analogues incorporating an aromatic,and heterocyclic type C-terminus: design,synthesis and biological evaluation

A representative series of structural analogs of the antimitotic tripeptides hemiasterlins have been designed and synthesized, as potential inhibitors of tubulin polymerization. Relying also on a computational approach, we aimed to explore unknown extensive changes at the C-fragment, by incorporating the conformationally required double bond into five- and six-membered rings. Key steps of the synthetic strategy are a dynamic resolution affording the A-fragment in 97 % ee and the preparation of six new cyclic C fragments, all potentially able to interact with tubulin by means of H bonds. Unexpectedly, biological evaluation of these analogs did not provide evidences neither for cytotoxic effect nor for inhibition of tubulin polymerization.     

Crystalline Intermediates during Polycondensation Reactions in the C–N–Cl System – The Paddle‐Wheel Molecule N(C6N7Cl2)3

Solid state metathesis reactions between cyanuric chloride and C–N–H or alkali metal–(B–)C–N compounds, respectively, were carried out in the temperature range between 150 °C to 500 °C, studying intermediate stages of reactions and targeting the formation of carbon nitride materials by elimination of HCl or alkali metal chlorides. Although cyanuric chloride was reacted with quite a number of different reaction partners such as melamine, cyanamide, lithium nitride, lithium or sodium carbodiimide, lithium nitridoborate or sodium dicyandiamide, always the same intermediate compounds appeared in the reactions mixtures. Colorless, needle‐shaped crystals of the tertiary amine N(C₃N₃Cl₂)₃ ( 1 ) were obtained at temperatures around 200–250 °C. Temperatures as high as 400 °C yielded yellow, plate‐like crystals of the heptazine compound C₆N₇Cl₃ ( 2 ). At even higher temperatures, the reaction products were of poorer crystallinity, but evidence of the formation of another crystalline intermediate was given by X‐ray powder diffraction and electron diffraction experiments. This third intermediate is assumed to be a tertiary amine, quite similar to 1 , however, having heptazine ligands instead of triazine ligands and is assigned with the formula N(C₆N₇Cl₂)₃ ( 3 ). Theoretical calculations were performed for the structures and the vibrational spectra of 1 and 3 . Theoretical calculations and a structure refinement based of X‐ray powder diffraction data yielded a plausible structural model for compound 3 .     

Wonderful Models for Generalized Dowling Arrangements

Order - For any triple given by a positive integer n, a finite group G, and a faithful representation V of G, one can describe a subspace arrangement whose intersection lattice is a generalized...     

Study of the release of gallic acid from (–)‐epigallocatechin gallate in old oolong tea by mass spectrometry

Liquid chromatography combined with multiple‐stage mass spectrometry (LC/MSⁿ) was used to study the pathway of the release of gallic acid (GA) from epigallocatechin gallate (EGCG) in infusion of old oolong tea. The possibility of releasing GA from EGCG in old tea preparations was supported by an in vitro observation of GA degraded from EGCG under heating conditions mimicking the drying process. Negative electrospray ionization with the data‐dependent mode of MSⁿ was used to study the formation pathway of GA in old oolong tea. The MSⁿ data show that GA was released from the dimer of EGCG, not directly degraded from EGCG. Copyright © 2010 John Wiley & Sons, Ltd.     

Giant Pores in a Chromium 2,6‐Naphthalenedicarboxylate Open‐Framework Structure with MIL‐101 Topology

Large, larger, …? Replacement of 1,4‐benzenedicarboxylate by 2,6‐naphthalenedicarboxylate in the MIL‐101 structure leads to an isoreticular mesoporous framework containing cages with diameters of 39 and 46 Å. High‐throughput methods are employed to determine appropriate reaction conditions. The microcrystalline compound is characterized by molecular simulation techniques, powder X‐ray diffraction, N₂‐sorption, and TEM investigations.

     

Corrective meshless particle formulations for time domain Maxwell''s equations

In this paper a meshless approximation of electromagnetic (EM) field functions and relative differential operators based on particle formulation is proposed. The idea is to obtain numerical solutions for EM problems by passing up the mesh generation usually required to compute derivatives, and by employing a set of particles arbitrarily placed in the problem domain. The meshless Smoothed Particle Hydrodynamics method has been reformulated for solving the time domain Maxwell's curl equations. The consistency of the discretized model is investigated and improvements in the approximation are obtained by modifying the numerical process. Corrective algorithms preserving meshless consistency are presented and successfully used. Test problems, dealing with even and uneven particles distribution, are simulated to validate the proposed methodology, also by introducing a comparison with analytical solution.