Justo Cobo

Synthesis of novel pyrazolic analogues of chalcones and their 3-aryl-4-(3-aryl-4,5-dihydro-1H-pyrazol-5-yl)-1-phenyl-1H-pyrazole derivatives as potential antitumor agents

Novel (E)-1-aryl-3-(3-aryl-1-phenyl-1H-pyrazol-4-yl)prop-2-en-1-ones 5/6 (pyrazolic chalcones) were synthesized from a Claisen-Schmidt reaction of 3-aryl-1-phenylpyrazol-4-carboxaldehydes 4 with several acetophenone derivatives 1. Subsequently, the microwave-assisted cyclocondensation reaction of chalcones 5/6 with hydrazine afforded the new racemic 3-aryl-4-(3-aryl-4,5-dihydro-1H-pyrazol-5-yl)-1-phenyl-1H-pyrazoles 7 or their N-acetyl derivatives 8 and 9 when reactions where carried out in DMF or acetic acid, respectively. Several of these compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines, where 5c and 9g showed remarkable activity mainly against leukemia (K-562 and SR), renal cancer (UO-31) and non-small cell lung cancer (HOP-92) cell lines, with the most important GI50 values ranging from 0.04 to 11.4 microM, from the in vitro assays.

Regioselective synthesis of 4,7,8,9-tetrahydro-2H-pyrazolo[3,4-b]quinolin-5(6H)-ones. Mechanism and structural analysis

Abstract Reactions of 5-amino-3-methyl-1H-pyrazole with dimedone and aldehydes afford regioselectivelly tricyclic linear 3,7,7-trimethyl-4,7,8,9-tetrahydro-2H-pyrazolo[3,4-b]quinolin-5(6H)-ones in good yields. Several aspects on this regioselective reaction, such as the reaction mechanism and structural studies of the predominant tautomeric form, are treated.

Synthesis of novel quinoline-2-one based chalcones of potential anti-tumor activity.

Novel quinoline-2-one based chalcones were synthesized from a Claisen-Schmidt condensation by using the couple KOH/1,4-dioxane as reaction medium. A relatively stable aldol was isolated and identified as the intermediate species in the formation of the target chalcones. Nine of the obtained compounds were in vitro screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 16c, 16d, 16h and 27 exhibited the highest activity, being compound 27 the most active, displaying remarkable activity against 50 human tumor cell lines, thirteen of them with GI(50) values ≤1.0 μM, being the HCT-116 (Colon, GI(50) = 0.131 μM) and LOX IMVI (Melanoma, GI(50) = 0.134 μM) the most sensitive strains. Compound 27 was referred to in vivo acute toxicity and hollow fiber assay by the Biological Evaluation Committee of the NCI. The acute toxicity study indicated that compound 27 was well tolerated intraperitoneally (150 mg/kg/dose) by athymic nude mice. This compound may possibly be used as lead compound for developing new anticancer agents.

Synthesis of novel 1,2,5-trisubstituted benzimidazoles as potential antitumor agents

Novel methyl 1-(5-tert-butyl-1H-pyrazol-3-yl)-2-(aryl)-1H-benzo[d]imidazole-5-carboxylates 11 were synthesized by following a four-step strategy involving a nucleophilic aromatic displacement (S(N)Ar) and a solvent free approach as key steps for the formation of the desired products. Structure of intermediates and products were confirmed by X-ray diffraction as well as the tautomeric rearrangement suffered by the pyrazole moiety during the curse of the final cyclization process. Several of the obtained compounds were screened by the US National Cancer Institute (NCI) for their ability to inhibit 60 different human tumor cell lines. Products 11b and 11n exhibited the highest activity against a range of cancer cell lines with remarkable values in panels of Non-Small Cell Lung Cancer, Melanoma and Leukemia, with GI(50) range of 1.15-7.33 μM and 0.167-7.59 μM, respectively, and suitable LC(50) with values greater than 100 μM.

Microwave induced synthesis of novel 8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines as potential antitumor agents

A series of new racemic 4-amino-6-aryl-8-(1,3-benzodioxol-5-yl)-8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines 4a-f and 4-amino-8-aryl-6-(1,3-benzodioxol-5-yl)-8,9-dihydro-7H-pyrimido[4,5-b][1,4]diazepines 5a-f were obtained regioselectively from the reaction of 4,5,6-triaminopyrimidine 1 with 1equiv of methylenedioxychalcones 2a-f and 3a-f, under microwave irradiation. Detailed NMR measurements confirm the high regioselectivity of this reaction. These compounds have been evaluated in the US National Cancer Institute (NCI) for their ability to inhibit approximately 60 different human tumor cell lines, where 4e, 5a and 5b presented remarkable activity against 47, 11 and 37 cancer cell lines, respectively, with the most important GI50 values ranging from 0.068 to 0.35 microM, in vitro assay.

Synthesis of new indeno[1,2-e]pyrimido[4,5-b][1,4]diazepine-5,11-diones as potential antitumor agents

Novel racemic indeno[1,2-e]pyrimido[4,5-b][1,4]diazepine-5,11-diones 3-29 were obtained regioselectivily from the reaction of 5,6-diamino-3,4-dihydropyrimidin-4-ones 1 and 2-arylideneindandiones 2 as reagents. These compounds have been evaluated at the US National Cancer Institute (NCI) for their ability to inhibit approximately 60 different human tumor cell lines, where 5 and 6 presented remarkable activity against 57 and 48 cancer cell lines, respectively, with the most important GI(50) values ranging from 0.49 to 1.46 microM, in vitro assay.

Molecular modeling study of dihydrofolate reductase inhibitors. Molecular dynamics simulations, quantum mechanical calculations, and experimental corroboration.

A molecular modeling study on dihydrofolate reductase (DHFR) inhibitors was carried out. By combining molecular dynamics simulations with semiempirical (PM6), ab initio, and density functional theory (DFT) calculations, a simple and generally applicable procedure to evaluate the binding energies of DHFR inhibitors interacting with the human enzyme is reported here, providing a clear picture of the binding interactions of these ligands from both structural and energetic viewpoints. A reduced model for the binding pocket was used. This approach allows us to perform more accurate quantum mechanical calculations as well as to obtain a detailed electronic analysis using the quantum theory of atoms in molecules (QTAIM) technique. Thus, molecular aspects of the binding interactions between inhibitors and the DHFR are discussed in detail. A significant correlation between binding energies obtained from DFT calculations and experimental IC₅₀ values was obtained, predicting with an acceptable qualitative accuracy the potential inhibitor effect of nonsynthesized compounds. Such correlation was experimentally corroborated synthesizing and testing two new inhibitors reported in this paper.

Microwave-assisted synthesis of pyrimido[4,5-b][1,6]naphthyridin-4(3H)-ones with potential antitumor activity

The 6,7,8,9-tetrahydropyrimido[4,5-b][1,6]naphthyridin-4(3H,5H,10H)-ones 4,5a-g and their oxidized forms 6,7a-g were obtained from the catalyst-free reaction of 6-amino-2-methylthiopyrimidin-4(3H)-one 3 and (E)-3,5-bis(benzylidene)-1-alkyl-4-piperidones 1,2a-g under Microwave irradiation and their subsequent oxidation process with p-chloranil. Eighteen of the new compounds were evaluated in the US National Cancer Institute (NCI), where compound 4g presented a remarkable activity against 57 cancer cell lines, with the most important GI(50) values ranging from 1.48 to 9.92 μM from in vitro assays.

Efficient catalyst-free four-component synthesis of novel γ-aminoethers mediated by a Mannich type reaction.

Herein, it is provided an efficient and one-pot procedure for the synthesis of novel and diversely substituted γ-aminoethers in good yields through a four-component process by treatment of benzylamines with polyformaldehyde and activated alkenes in aliphatic alcohols acting both as solvent and as etherificant agents. Reactions proceeded via a Mannich-type reaction, where the formation of iminium ions and aminals was identified as the key intermediates to obtain the target products.

New aspects on the selective synthesis of 7-arylpyrido[2,3-d]pyrimidines

Pyrido[2,3-d]pyrimidines have been synthesized via a selective cyclocondensation reaction between 6-aminopyrimidines 1 and the Mannich bases, propiophenone hydrochlorides 2. Intermediates for this reaction, such as the Michael addition adduct and the further hydrated pyrido[2,3-d]pyrimidine were isolated to prove the postulated mechanism. NMR analysis of bidimensional experiments allowed to determine unambiguously the process to obtain 7-arylpyrido[2,3-d]pyrimidines.