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  • Open access
  • 79 Reads
STUDY OF A NEW HYDRAZONE SYSTEM WITH ION COMPLEXATION CAPACITY SUITABLE FOR SELECTIVE DETECTION.

The design and synthesis of chemosensors that allows the selectively detection of heavy metal cations by complexation, is an area of ​​growing interest. The hydrazone functional group has been widely used in supramolecular chemistry due to its complexing capacity, its conjugated electrons and its simple methods of synthesis. In this way, a nitrogen system derived from the condensation of vanillin (aromatic aldehyde) and 2-hydrazino benzothyazol to give the corresponding hydrazone for the detection of Cu2+ was developed. Spectroscopic determinations demonstrate whether the complexing took place. The hidrazone showed a response in UV-vis spectroscopy and a color shift is observed with the naked eye. In addition, theoretical analysis based on the density functional theory (DFT) was realized. The geometries of the benzothiazole hydrazone derived from vanillin (ligand) and its analog Cu2+-ligand complex were optimized at the B3LYP/631+G(d,p) level of theory. The adsorption spectra of this molecular system were analyzed and compared with experimental data. Theoretical study of the structural, electronics and optical properties allowed to understand the chemical changes that the ligand suffers in the complexation process with the Cu+2 ion.

  • Open access
  • 38 Reads
Polyphenols from Thelesperma megapotamicum and their antioxidant and neuroprotective activities

Polyphenols are attracting increasing attention to the discovery of useful agents for the treatment of neurodegenerative diseases.

Thelesperma megapotamicum (Spreng.) Kuntze belongs to the family Asteraceae which is known to have a high antioxidant capacity.

The phytochemical investigation of T. megapotamicum revealed the presence of 1’-S-acetoxyeugenol isobutyrate (1), 1’-S-isobutyroxyeugenol isobutyrate (2), stigmasterol (3), b-sitosterol (4), lupeol (5), luteolin (6), eriodictyol (7), and marein (8), as major secondary metabolites. Compounds 1-5, and 7 were isolated for the first time from T. megapotamicum.

The neuroprotective activity of this species was studied by evaluating the inhibition in vitro of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE), and antioxidant capacity of the sub-extracts and of the major metabolites isolated from them. The AChE and BChE inhibition were determined by Ellman’s method and the antioxidant activity by DPPH assay.

The chloroform (IC50 = 30.7 ± 1.5 μg/mL) and n-butanol sub-extracts (IC50 = 60.3 ± 2.3 μg/mL) were the most active against BChE. Metabolites 1, 2 and 8, isolated from these sub-extracts, exhibited the highest activity against this enzyme, with IC50 values of 59.0 ± 2.1 μM, 46.4 ± 1.2 μM, and 51.6 ± 2.3 μM, respectively.

The ethyl acetate (IC50 = 19.6 ± 0.7 μg/mL) and n-butanol sub-extracts (IC50 = 49.5 ± 2.2 μg/mL) showed an interesting antioxidant activity. Compounds 6, 7 and 8, obtained from these sub-extracts, were the most active, with IC50 values of 19.1 ± 2.8 μM, 17.9 ± 1.2 μM, and 78.6 ± 1.7 μM, respectively.

The inhibitory activity against BChE and antioxidant capacity of the polyphenols present in T. megapotamicum highlight this species as a promising source of active metabolites for the development of agents for the treatment of neurodegenerative diseases.

  • Open access
  • 109 Reads
6-Amino-4-aryl-3-carbamoyl-5-cyano-1,4-dihydropyridine-2-thiolates: Synthesis, reactions and docking studies

New triethylammonium 6-amino-4-aryl-3-carbamoyl-5-cyano-1,4-dihydropyridine-2-thiolates were prepared in good yields by ternary condensation of malononitrile, aldehydes and monothiomalonamide (3-amino-3-thioxopropanamide) in the presence of Et3N. The thiolates undergo S-alkylation under mild conditions to give new 1,4-dihydronicotinamides. Molecular docking studies were carried out in order to explore the interaction mechanism and to investigate suitable binding modes of the new compounds on the calcium channel proteins. Some of the compounds in experiments in silico were found to be more potent as calcium channel blockers than reference drug Nifedipine.

  • Open access
  • 71 Reads
Synthesis of tetrakis-tetrazole via a repetitive MCR

The synthesis of two novel and complex molecules tetrakis-tetrazole were synthesized via a Ugi-azide repetitive reaction from easily accessible starting materials in good yields. The use of orthogonal bifunctional reagents in isocyanide based multicomponent reactions (IMCR) allowed us the synthesis of structurally complex molecules in one pot manner. The molecules herein synthesized could have applications, such as chelating agents and organocatalysis.

  • Open access
  • 73 Reads
Synthesis of peptidomimetics via IMCR/post-transformation strategy

A series of three 2,5-diketopiperazine (DKP’s) were synthesized via one-pot process through the post-IMCR-transformation strategy. This strategy emphasizes the role of orthogonal bifunctional reagents in the IMCR process to increase their synthetic potential, allowing us accessing a synthetic platform from which it is possible to obtain privileged heterocyclic peptidomimetics via lactamization reaction.

  • Open access
  • 53 Reads
New reactions of 5-amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile

5-Amino-3-(cyanomethyl)-1H-pyrazole-4-carbonitrile, prepared by reaction of malononitrile dimer with hydrazine, smoothly react with chloroacetyl chloride to afford 2-chloro-N-(4-cyano-3-(cyanomethyl)-1H-pyrazol-5-yl)acetamide in good yield. The latter easily react with 3-cyanopyridine-2-thiolates to give hybrid molecules bearing nicotinonitrile and pyrazole units.

  • Open access
  • 45 Reads
The reactions of N,N'-diphenyldithiomalonamide with Michael acceptors

N,N'-diphenyldithiomalonamide (dithiomalondianilide) smoothly reacts with various Michael acceptors to give either stable Michael adducts or products of their further heterocyclization. The structure of the products was confirmed by 2D NMR experiments and X-ray data. The mechanisms of the reactions are discussed.

  • Open access
  • 74 Reads
N-(Thieno[2,3-b]pyridin-3-yl)cyanoacetamides: synthesis and cyclizations

A series of N-(thieno[2,3-b]pyridin-3-yl)cyanoacetamides were prepared by reaction of 3-aminothieno[2,3-b]pyridines with 1-cyanoacetyl-3,5-dimethytlpyrazole. Upon treatment with alkali, N-(2-alkoxycarbonylthieno[2,3-b]pyridin-3-yl)cyanoacetamides undergo Camps-type cyclization to give dipyridothiophenes. The relative stability of their tautomers was estimated by quantum chemical calculations. In contrast, cyclization of 3-(2-cyanoacetamido)thieno[2,3-b]pyridine-2-carboxamides lead to the formation of pyrido[3’,2’:4,5]thieno[3,2-d]pyrimidines.

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