Jorge Trilleras

A Novel Class of Selective Acetylcholinesterase Inhibitors: Synthesis and Evaluation of (E)-2-(Benzo[d]thiazol-2-yl)-3-heteroarylacrylonitriles

(E)-2-(benzo[d]thiazol-2-yl)-3-heteroarylacrylonitriles are described as a new class of selective inhibitors of acetylcholinesterase (AChE). The most potent compound in the series exhibited good AChE inhibitory activity (IC50 = 64 µM). Compound 7f was found to be more selective than galanthamine in inhibiting AChE and it showed a moderate selectivity index. Kinetic studies on AChE indicated that a competitive type of inhibition pattern exist for these acrylonitrile derivates. Molecular docking models of the ligand-AChE complexes suggest that compound 7g is located on the periphery of the AChE active site.

Microwave-assisted synthesis under solvent-free conditions of (E)-2-(Benzo[d]thiazol-2-yl)-3-arylacrylonitriles

Uma serie de (E)-2-(benzo[d]tiazol-2-il)-3-arilacrilonitrilas foi sintetizada pela condensacao de Knoevenagel assistida por microondas, na ausencia de solvente, partindo do correspondente 2-(benzo[d]tiazo-2-il)acetonitrila e aldeidos aromaticos, contendo tanto grupos doadores de eletrons, como retiradores. Os tempos de reacao foram consideravelmente curtos e os produtos, obtidos em rendimentos moderados (50-75%) e boa pureza. A configuracao da dupla ligacao da acrilonitrila nao pode ser estabelecida por metodos comuns de RMN. No entanto, estudos teoricos sugerem que nesses compostos o isomero E e mais estavel do que o Z, o que esta de acordo com algumas evidencias experimentais. A series of (E)-2-(benzo[d]thiazol-2-yl)-3-arylacrylonitriles was synthesized by microwave assisted Knoevenagel condensation under solvent-free conditions from the corresponding 2-(benzo[d]thiazol-2-yl)acetonitrile and aromatic aldehydes with electrondonating/electronwithdrawing groups. The reaction times were considerably short and the products obtained in moderate yields (50 to 75%) and good purity. The configuration of the acrylonitrile double bond could not be established by regular NMR methods. However, theoretical studies suggest that the E isomer is more stable than Z, which is in good agreement with some experimental evidences.

Ultrasound-assisted phase-transfer catalysis method in an aqueous medium to promote the Knoevenagel reaction: Advantages over the conventional and microwave-assisted solvent-free/catalyst-free method

Given the broad spectrum of uses of acrylonitrile derivatives as fluorescent probes, AChE inhibitors, and others, it is necessary to find easy, efficient and simple methods to synthesize and diversify these compounds. We report the results of a comparative study of the effects of three techniques on the reactions between heterocyclic aldehydes and 2-(benzo[d]thiazol-2-yl)acetonitrile: stirring; ultrasound coupled to PTC conditions (US-PTC); and MW irradiation (MWI) under solvent and catalyst-free conditions. The effects of conditions on reaction parameters were evaluated and compared in terms of reaction time, yield, purity and outcomes. The US-PTC method is more efficient than the MWI and conventional methods. The reaction times were considerably shorter, with high yields (>90%) and good levels of purity. In addition, X-ray diffraction analysis and quantum mechanical calculations, at the level of density functional theory (DFT), ratify obtaining acrylonitrile isomers with E configurations. The crystal structure of 3c is stabilized by weak C-Ho⋯N intermolecular interactions (Ho⋯NC=2.45 Å, Co⋯NC=3.348(3) Å, Ho⋯NC=162°), forming centrosymmetric ring R2(2) (20) along the crystallographic a axis.

N6-Substituted 2-amino-4-chloro-5-formylpyrimidines: puckered versus planar pyrimidine rings, and hydrogen-bonded aggregation in zero, one, two and three dimensions

The structures of 12 new N(6)-substituted 2-amino-4-chloro-5-formylpyrimidines, where the N(6) substituent is of the type NHR or NR(1)R(2), have been determined. The intramolecular dimensions provide strong evidence for the development of polarized, charge-separated molecular-electronic structures, with the positive charge delocalized over the two exocyclic amino N atoms and with negative charge on the formyl O atom. This polarization appears to be independent of the significant puckering, in seven of the compounds, of the pyrimidine rings from planarity towards boat, twist-boat or screw-boat conformations. In 11 of the compounds studied here, N-H...N hydrogen bonds link pairs of molecules into centrosymmetric R2(2)(8) dimer units, and their overall crystal structures are determined by the patterns of hydrogen bonds by which these units are further linked. Examples are reported in which no further hydrogen bonding occurs; in which the R2(2)(8) dimers are linked into chains of rings, or into sheets; and in which sheets are formed by the pi-stacking of hydrogen-bonded chains of rings. In the sole structure lacking the R2(2)(8) dimer motif, N-H...O and N-H...N hydrogen bonds cooperate to generate a three-dimensional framework structure.

Facile sonochemical synthesis of novel pyrazolyne derivates at ambient conditions.

Claisen-Schmidt condensation reaction of 4-acetamidoacetophenone with aromatic aldehydes under ultrasonic irradiation affords acetylaminochalcones (yields: 71-90%) which also under ultrasonic irradiation and in the presence of sodium acetate and acetic acid aqueous undergo facile and clean cyclocondensation with hydrazine to afford 3-(4-acetamidophenyl)-5-(aryl)-1-H-pyrazolines. The pyrazolines were obtained in good to excellent yields (81-89%), and were characterized by conventional spectral data. The work-up is simple and the results obtained indicate that, unlike classical heating, ultrasonic irradiation results in higher yields, shorter reaction times (1.5-2.3 h) and milder conditions.

Supramolecular aggregation in three 4-aryl-6-(1H-indol-3-yl)-3-methyl-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitriles.

Both 6-(1H-indol-3-yl)-3-methyl-4-(4-methylphenyl)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile and 6-(1H-indol-3-yl)-3-methyl-4-(4-methoxyphenyl)-1-phenyl-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile crystallize from dimethylformamide solutions as stoichiometric 1:1 solvates, viz. C(29)H(21)N(5).C(3)H(7)NO, (I), and C(29)H(21)N(5)O.C(3)H(7)NO, (II), respectively; however, 6-(1H-indol-3-yl)-3-methyl-1-phenyl-4-(3,4,5-trimethoxyphenyl)-1H-pyrazolo[3,4-b]pyridine-5-carbonitrile, C(31)H(25)N(5)O(3), (III), crystallizes in the unsolvated form. The heterocyclic components of (I) are linked by C-H...pi(arene) hydrogen bonds to form cyclic centrosymmetric dimers, from which the solvent molecules are pendent, linked by N-H...O hydrogen bonds. In (II), the heterocyclic components are linked by a combination of C-H...N and C-H...pi(arene) hydrogen bonds into chains containing two types of centrosymmetric ring, and the pendent solvent molecules are linked to these chains by N-H...O hydrogen bonds. Molecules of (III) are linked into simple C(12) chains by an N-H...O hydrogen bond, and these chains are weakly linked into pairs by an aromatic pi-pi stacking interaction.

(E)-3-{2-amino-4-ethoxy-6-[N-(4-methoxyphenyl)-N-methylamino]pyrimidin-5-yl}-1-phenylprop-2-en-1-one: a boat-shaped pyrimidine ring and a chain of hydrogen-bonded R4(2)(8) and R2(2)(20) rings.

In the title compound, C23H24N4O3, the pyrimidine ring adopts an almost perfect boat conformation, and the bond distances provide evidence for some polarization of the molecular-electronic structure. Two independent N-H...O hydrogen bonds link the molecules into chains of edge-fused R2(4)(8) and R2(2)(20) rings.

Novel (E)-1-(pyrrole-2-yl)-3-(aryl)-2-(propen-1-one) derivatives as efficient singlet oxygen quenchers: kinetics and quantum chemical calculations

Chalcones constitute an important group of natural and synthetic products that have been screened due to their wide range of pharmacological applications. Herein, we studied the antioxidant activity of five newly synthetized (E)-1-(pyrrole-2-yl)-3-(aryl)-2-(propen-1-one) (PAPs) derivatives against singlet oxygen (1O2). The differences among the compounds are related to aryl substitution in the p-position where: 3a = C6H5, 3b = 4-H3COC6H4, 3c = 4-FC6H4, 3d = 4-ClC6H4, 3e = 4-BrC6H4. The PAPs were synthesized using a Claisen–Schmidt condensation reaction between 2-acetylpyrrole and aromatic aldehydes under ultrasonic irradiation (yields between 79–86%) and were characterized by IR, mass spectrometry, NMR and quantum chemical calculations. The total singlet oxygen quenching rate constants (kQ) of the PAPs were measured spectrophotometrically in ethanol at 25 °C and determined by using the Stern–Volmer model. As the character of the EWGs is increased from 3a to 3e, the kQ diminishes smoothly. The best quencher is found to be the 3a compound (where the aryl group is unsubstituted) with a kQ = 5.71 (±0.21) × 107 M−1 s−1, which is similar to those for other antioxidants e.g. flavonoids. These results suggest these compounds are efficient quenchers of singlet oxygen and their potential applicability in biological systems.

N-(4-((E)-3-arylacryloyl)phenyl)acetamide derivatives and their antileishmanial activity

The antileishmanial activity of a series of enonic derivatives (chalcones) synthesized via Claisen-Schmidt condensation reactions assisted by ultrasonic radiation was characterized by analyzing their cytotoxicity against Leishmania (Viannia) panamensis promastigotes, a species responsible for over 90% of Leishmania cases in Colombia. Two compounds were active against Leishmania with selectivity indexes of LC50 EC50-1 (lethal concentration 50 and effective concentration 50) higher than 27 and 3, respectively. These results suggest that a substitution on one of the two chalcone rings (aromatic ring A) with oxygen is convenient. Compound 3g should be further investigated for its antileishmanial activity, especially for being easy to obtain in high yields, making it possible to produce drugs for the treatment of cutaneous leishmaniasis.

Efficient Microwave-Assisted Synthesis of 5-Deazaflavine Derivatives

A series of pyrimido[4,5-b]quinolines (5-deazaflavines), were synthesized by microwave assisted intramolecular cyclization. The N4-substituted-2,4-diamino-6-chloro-pyrimidine-5-carbaldehydes, were prepared by selective monoamination of 2-amino-4,6-dichloropyrimidine-5-carbaldehyde with aliphatic and aromatic amines.