A new fluorescent functionalized amino acid, 4-chloromethylcoumarin-6-yl-alanine, was used in the synthesis of an amino acid conjugate by coupling with a model N-protected alanine, through an ester linkage. The photophysical properties of the fluorescent conjugate are presented, as well as its behaviour towards photocleavage by irradiation in methanol/HEPES buffer (80:20) solution, in a photochemical reactor at different wavelengths (254, 300, 350 and 419 nm), followed by HPLC/UV and 1H NMR monitoring.

The novel functionalised oxygen heterocycle 4-(hydroxymethyl)-6-methoxy-2-oxo-2H-benzo[h]benzopyran was synthesised and used in the preparation of a fluorescent ß-alanine conjugate. In order to evaluate its photosensitivity, photocleavage reaction in methanol/HEPES buffer (80:20) solution at different wavelengths of irradiation (250, 300 and 350 nm) was carried out and photocleavage kinetic data were obtained.

test abstract

The concept of bond-based quadratic indices is generalized to codify chemical structure information for chiral drugs, making use of a trigonometric 3D-chirality correction factor. In order to evaluate the effectiveness of this novel approach in drug design, we have modeled several well-known data sets. In particularly, Cramer's steroid data set has become a benchmark for the assessment of novel QSAR methods. This data set has been used by several researchers using 3D-QSAR approaches. Therefore, it is selected by us for the shake of comparability. In addition, to evaluate the effectiveness of this novel approach in drug design, we model the angiotensin-converting enzyme inhibitory activity of perindoprilate's σ-stereoisomers combinatorial library, as well as codify information related to a pharmacological property, highly dependent on the molecular symmetry, of a set of seven pairs of chiral N-alkylated 3-(3-hydroxyphenyl)-piperidines, which bind σ-receptors. The validation of this method is achieved by comparison with earlier publications applied to the same data sets. The non-stochastic and stochastic bond-based 3D-chiral quadratic indices appear to provide a rather interesting alternative to other more common 3D-QSAR descriptors.

The non-stochastic and stochastic atom-based quadratic indices are applied to develop quantitative structure-activity relationship (QSAR) models for the prediction of aquatic toxicity. The used dataset, consisting of 392 benzene derivatives for which toxicity data to the ciliate Tetrahymena pyriformis were available, is divided into training and test sets. The obtained multiple linear regression models are statistically significant (R2 = 0.787 and s = 0.347, R2 = 0.806 and s = 0.329, for non-stochastic and stochastic quadratic indices, respectively) and show rather good stability in a cross-validation experiment (q2 = 0.769 and scv = 0.357, q2 = 0.791 and scv = 0.337, correspondingly). In addition, a validation through an external test set is performed, which yields significant values of R2 pred of 0.745 and 0.742. The comparison with other approaches exposes a good behavior of our method of predicting the aquatic toxicity of benzenes. The obtained results suggest that, the non-stochastic and stochastic quadratic indices seem to provide an interesting alternative to costly and timeconsuming experiments for determining toxicity.

In this work, we have studied from a theoretical perspective the electronic properties such as HOMO → LUMO excitation energy, ionization potential and reorganization energy of oligotiophenes and their alkyl and alcoxy derivatives. The effect of charge injection was also studied. The oligomeric approximation was employed in order to calculate the band gap and ionization potential of an ideal polymeric chain for each one of the selected systems. The variation of reorganization energy on the backbone length was also analyzed.

The mechanism of ketonization of acetic acid over SiO₂ was investigated by semiempirical quantum chemical AM1 method using the cluster approach. It has been found that the adjacent acid-base pair of the catalytic sites provokes dissociative adsorption of the acetic acid molecules resulting in the formation of surface carboxylate species. The adsorption process proceeds spontaneously. After blocking the acid-base pairs of catalyst, the new portions of acetic acid molecules interact with active species in the gas phase, converting into acyl cations. The adsorbed carboxylate species is attacked from the methyl group side by the acyl cation resulting in the formation of an acetone molecule and CO₂ by bimolecular electrophilic substitution reaction.

This work presents the results obtained in the characterization and development of gold nanoparticles (AuNPs) immobilized onto two kinds of gel-supported Ionic Liquids (gel-Supported Ionic Liquid like phases, g-SILLPs) and their study as catalysts for the oxidation of organic compounds. The benchmark reaction selected for this purpose was the oxidation of 1-phenylethanol. Besides, the reactions were performed under the concept of the exploitation of enabling techniques using: Microwave heating (as the energy source), water (as the solvent), hydrogen peroxide (as a benign oxidant agent), and supported catalysts (providing a more efficient catalytic processes and easy recovery of the catalyst).

Microporus materials are active catalysts in regioselective synthesis of pyrimidobenzimidazoles. Five kinds of zeolites were studied and they showed quite different catalytic activities due to their wide acid sites distributions and various pore structures. Hβ zeolite was found to be the best in activity for synthesis of isomer 5 while the basic catalyst NaY zeolite found suitable for synthesis of isomers 4. The main acid sites of H-zeolites were Brönsted acid sites, and H+ was the catalytic acid site. The methodology involves a ring closure by different ways based on the reaction medium was confirmed by NOE and X-ray studies.

Some phthalein dyes have been synthesized by the condensation of phthalic anhydride with various phenols through a novel route of microwave irradiation technique under solvent free condition in high yields within minutes. The inexpensive, solvent free and fast reaction conditions are the important features of this procedure.