The Biginelli Reaction with an Imidazolium–Tagged Recyclable Iron Catalyst: Kinetics,Mechanism, and Antitumoral Activity

The present work describes the synthesis, characterization, and application of a new ion‐tagged iron catalyst. The catalyst was employed in the Biginelli reaction with impressive performance. High yields have been achieved when the reaction was carried out in imidazolium‐based ionic liquids (BMI ? PF₆, BMI ? NTf₂, and BMI ? BF₄), thus showing that the ionic‐liquid effects play a role in the reaction. Moreover, the ion‐tagged catalyst could be recovered and reused up to eight times without any noticeable loss in activity. Mechanistic studies performed by using high‐resolution electrospray‐ionization quadrupole‐time‐of‐flight mass (HR‐EI‐QTOF) spectrometry and kinetic experiments indicate only one reaction pathway and rule out the other two possibilities under the development conditions. The theoretical calculations are in accordance with the proposed mechanism of action of the iron catalyst. Finally, the 37 dihydropyrimidinone derivatives, products of the Biginelli reaction, had their cytotoxicity evaluated in assays against MCF‐7 cancer cell linages with encouraging results of some derivatives, which were virtually non‐toxic against healthy cell linages (fibroblasts).     

Laser direct writing of combinatorial libraries of idealized cellular constructs: Biomedical applications

The ability to control cell placement and to produce idealized cellular constructs is essential for understanding and controlling intercellular processes and ultimately for producing engineered tissue replacements. We have utilized a novel intra-cavity variable aperture excimer laser operated at 193 nm to reproducibly direct write mammalian cells with micrometer resolution to form a combinatorial array of idealized cellular constructs. We deposited patterns of human dermal fibroblasts, mouse myoblasts, rat neural stem cells, human breast cancer cells, and bovine pulmonary artery endothelial cells to study aspects of collagen network formation, breast cancer progression, and neural stem cell proliferation, respectively. Mammalian cells were deposited by matrix assisted pulsed laser evaporation direct write from ribbons comprised of a UV transparent quartz coated with either a thin layer of extracellular matrix or triazene as a dynamic release layer using CAD/CAM control. We demonstrate that through optical imaging and incorporation of a machine vision algorithm, specific cells on the ribbon can be laser deposited in spatial coherence with respect to geometrical arrays and existing cells on the receiving substrate. Having the ability to direct write cells into idealized cellular constructs can help to answer many biomedical questions and advance tissue engineering and cancer research.     

Methods for the structural investigation of xanthones: Part II. Location of hydroxyl groups by ultraviolet and visible spectroscopy1

Ultraviolet spectral shifts in presence of certain additives may be used to determine the hydroxylation pattern of xanthones. Thus, 3-hydroxyxanthones are characterized by an intense band around 355 nm which appears in presence of sodium hydroxide, o- and p-Dihydroxyxanthones decompose in presence of this reagent, the reaction rate depending on the position of the substituents. While the spectra of 1-and 2-hydroxyxanthones do not suffer modification in presence of sodium acetate, 3- and 4-hydroxy groups produce typical shifts which are dependent on the presence of additional oxygen functions. The spectra of 1-hydroxy-, as well as of o-dihydroxyxanthones, are affected by the addition of aluminum chloride. 1- and 4-Hydroxy groups with unsubstituted p-positions may be detected and distinguished through the visible spectrum (350–750 nm) of the reaction product of the xanthone with 2,6-dichlorobenzoquinone chloroimide (Gibbs test). Relatively acidic hydroxyls give rise to two maxima in this region. Two maxima, even if of different relative intensity, are also obtained with o- and p-dihydroxy-, as well as with o- and p-hydroxyallylxanthones.     

Rapid analysis of isomeric exogenous metabolites by differential mobility spectrometry-mass spectrometry

The direct separation of isomeric glucuronide metabolites from propranolol dosed tissue extracts by differential mobility spectrometry-mass spectrometry (DMS-MS) with the use of the polar gas-phase chemical modifier acetonitrile was demonstrated. The DMS gas-phase separation was able to resolve the isomeric metabolites with separation times on the order of milliseconds instead of minutes which is typically required when using pre-ionization chromatographic separation methods. Direct separation of isomeric metabolites from the complex tissue extract was confirmed by implementing a high-performance liquid chromatography (HPLC) separation prior to the DMS-MS analysis to pre-separate the species of interest. The ability to separate isomeric exogenous metabolites directly from a complex tissue extract is expected to facilitate the drug development process by increasing analytical throughput without the requirement for pre-ionization cleanup or separation strategies.     

Hologram QSAR Models of 4-[(Diethylamino)methyl]-phenol Inhibitors of Acetyl/Butyrylcholinesterase Enzymes as Potential Anti-Alzheimer Agents

Hologram QSAR models were developed for a series of 36 inhibitors (29 training set and seven test set compounds) of acetyl/butyrylcholinesterase (AChE/BChE) enzymes, an attractive molecular target for Alzheimer's disease (AD) treatment. The HQSAR models (N = 29) exhibited significant cross-validated (AChE, q² = 0.787; BChE, q² = 0. 904) and non-cross-validated (AChE, r² = 0.965; BChE, r² = 0.952) correlation coefficients. The models were used to predict the inhibitory potencies of the test set compounds, and agreement between the experimental and predicted values was verified, exhibiting a powerful predictive capability. Contribution maps show that structural fragments containing aromatic moieties and long side chains increase potency. Both the HQSAR models and the contribution maps should be useful for the further design of novel, structurally related cholinesterase inhibitors.     

Superelectrophilic amidine dications: dealkylation by triflate anion

Superelectrophiles: Formamides were designed that when treated with triflic anhydride would be transformed into superelectrophilic amidine dications. These dications were so electrophilic that they underwent in?situ dealkylation by the triflate anion (see scheme; Tf=trifluoromethanesulfonyl). DFT calculations were used to determine the mechanistic details of the dealkylation reaction.