Pablo Machado

Solvent-Free Heterocyclic Synthesis

6.1. Oxadiazoles 4154 6.2. Diazaphospholes 4154 7. Six-Membered Heterocycles with One Heteroatom 4155 7.1. Pyridines 4155 7.2. Pyridinones 4155 7.3. Quinolines 4156 7.4. Quinolinones 4157 7.5. Isoquinolines 4157 7.6. Acridines 4158 7.7. Pyranones 4158 7.8. Flavones 4159 8. Six-Membered Heterocycles with Two Heteroatoms 4159 8.1. Pyridazinones 4159 8.2. Pyrimidines 4159 8.3. Pyrimidinones 4160 8.4. Quinazolines 4162 8.5. Quinazolinones 4162 8.6. Quinoxalines 4164 8.7. Quinoxalinediones 4165 8.8. Oxazines 4165 8.9. Oxazinones 4166 8.10. Thiazines 4166 9. Six-Membered Heterocycles with Three Heteroatoms 4166

Antinociceptive effect of novel trihalomethyl-substituted pyrazoline methyl esters in formalin and hot-plate tests in mice.

The aim of the present study was to evaluate the antinociceptive potential of four novel pyrazoline methyl ester compounds on chemical and thermal models of pain in mice. The following 5-trihalomethylated-4,5-dihydro-1H-pyrazole methyl ester compounds were tested: 3-methyl-5-trifluoromethyl-(MPF3), 4-methyl-5-trifluoromethyl-(MPF4), 3-methyl-5-trichloromethyl-(MPCl3) and 4-methyl-5-trichloromethyl-(MPCl4). MPF3, MPF4, MPCl3 and MPCl4 (0.03-1.0 mmol/kg) given intraperitoneally decreased neurogenic and inflammatory phases of nociception in the formalin test. Moreover, MPF3, MPF4, MPCl3, MPCl4 (0.1-1.0 mmol/kg) and dipyrone (1.5 mmol/kg) also produced a dose-dependent antinociceptive effect in the hot-plate test. However, MPF3, MPF4, MPCl3 and MPCl4 did not impair motor coordination in the rotarod test or spontaneous locomotion in the open field test. The antinociceptive effect of MPF4 (1.0 mmol/kg, i.p.) was reversed by the opioid receptor antagonist naloxone (2 mg/kg, i.p.), but not by the alpha(2)-adrenergic receptor antagonist yohimbine (0.15 mg/kg, i.p.) or by p-chlorophenylalanine ethyl ester (PCPA, 300 mg/kg, i.p.) treatment. In contrast to morphine (5 mg/kg, i.p.), MPF4 given daily for up to 8 days did not generate a tolerance to its antinociceptive effect. However, similar to morphine (11 mg/kg, i.p.), MPF4 reduced gastrointestinal transit in mice. Taken together these results demonstrate that these novel pyrazoline methyl esters tested may be promising prototypes of additional mild analgesics.

Cyclooxygenase-2/PGE2 pathway facilitates pentylenetetrazol-induced seizures

Cyclooxygenases (COXs) are rate-limiting enzymes in the metabolic pathways in which arachidonic acid is converted to prostaglandins. COX-2 is the isoform induced at injury/inflammation sites and expressed constitutively in a few tissues, such as the central nervous system, and plays a role in neurodegenerative diseases associated with increased excitatory activity. However, the role of COX-2 and its main product, prostaglandin E(2) (PGE(2)), in the convulsive states is not fully established. In this study we showed that the selective COX-2 inhibitor, celecoxib (at the dose of 2mg/kg, but not at the doses of 0.2 or 20mg/kg, p.o.), protects against the seizures induced by pentylenetetrazol (PTZ, 60 mg/kg, i.p.). The role of PGE(2) in the convulsions induced by PTZ was further investigated by administering anti-PGE(2) antibodies (4 microg/2 microl, i.c.v.), and assessing electroencephalographic changes induced by PTZ (PTZ, 60 mg/kg, i.p.). Anti-PGE(2) antibodies attenuated PTZ-induced seizures in rats. In addition, combining PGE(2) (100 ng/2 microl, i.c.v.) with a subconvulsant dose of PTZ (20mg/kg, i.p.) caused seizures, further supporting a role for this prostaglandin in the convulsions induced by PTZ. Finally, we showed that the anticonvulsant action of celecoxib (2mg/kg, p.o.) was reversed by the intracerebroventricular administration of PGE(2) (10 ng/2 microl, i.c.v.). These data constitute strong converging pharmacological evidence supporting a facilitatory role for the COX-2/PGE(2) pathway in the seizures induced by PTZ. However, whether selective COX-2 inhibitors are safer anti-inflammatory drugs for epileptic patients than nonspecific inhibitors remains to be determined.

Effect of 5-trifluoromethyl-4,5-dihydro-1H-pyrazoles on chronic inflammatory pain model in rats.

Nonsteroidal antiinflammatory drugs (NSAIDs) are commonly used for treatment of arthritis. However, their long-term use has been associated with considerable morbidity, limiting their application. Thus, there remains a need to develop new drugs for the effective and safe relief of chronic inflammatory pain. In this context, the present study was designed to evaluate the antinociceptive and antiedematogenic effects of the 5-trifluoromethyl-4,5-dihydro-1H-pyrazole derivatives EPFCA3 and MPFCA4 after acute (1-1000 micromol/kg) and chronic (100 micromol/kg for 15 days) administration in rats submitted to a model of adjuvant-induced arthritis. We also analyzed some biochemical indicators of toxicity (alanine aminotransferase, aspartate aminotransferase, urea and creatinine levels) after prolonged administration of these compounds. We found that acute and chronic subcutaneuous administration of EPFCA3 and MPFCA4 produces an antinociceptive, but not antiedematogenic, effect on the arthritis animal model induced by complete Freunds adjuvant (CFA). No signs of toxicity were observed in the animals chronically treated with EPFCA3 or MPFCA4. Dipyrone (1-1000 micromol/kg) was used as the positive control and its effect was similar to that of the novel pyrazoles. The activity of tissue myeloperoxidase, the tissue TNF-alpha level and the serum haptoglobin level was increased by intraplantar CFA injection. However, chronic administration of EPFCA3, MPFCA4 or dipyrone was not able to alter the relation between these parameters and inflammation. Our results suggest that EPFCA3 and MPFCA4 are good candidates for the development of new drugs for pain treatment.

Ultrasound promoted synthesis of 2-imidazolines in water: a greener approach toward monoamine oxidase inhibitors.

A series of sixteen 2-substituted-2-imidazolines (where the substituent R=Ph, Me-4-Ph; MeO-4-Ph; (MeO)(2)-3,4-Ph; (MeO)(3)-3,4,5-Ph; Ph-4-O-C(O)-Ph; Cl-4-Ph; Cl-2-Ph; Cl(2)-2,4-Ph; NO(2)-4-Ph; NO(2)-3-Ph; Naphth-2-yl; Fur-2-yl; Benzofur-2-yl; Pyridin-2-yl; Quinolin-2-yl) has been synthesized from the reaction of the substituted-aldehydes and ethylenediamine by ultrasound irradiation with NBS in an aqueous medium in high yields (80-99%). The 2-imidazoline ability to inhibit the activity of the A and B isoforms of monoamine oxidase (MAO) was investigated and some of them showed potent and selective MAO inhibitory activity especially for the MAO-B isoform and could become promising candidates for future development.

Antinociceptive action of 4-methyl-5-trifluoromethyl-5-hydroxy-4, 5-dihydro-1H-pyrazole methyl ester in models of inflammatory pain in mice.

AIMSnThe aim of the present study was to evaluate the antinociceptive effect of the novel pyrazoline methyl ester: 4-methyl-5-trifluoromethyl-5-hydroxy-4,5-dihydro-1H-pyrazole methyl ester (MPF4).nnnMAIN METHODSnThe effect of MPF4 was assessed in two models of pain: arthritic pain caused by Complete Freunds Adjuvant (CFA) and postoperative pain caused by surgical incision in mice.nnnKEY FINDINGSnMPF4 given intraperitoneally (1.0 mmol/kg, i.p.) produced marked antinociception in inflammatory allodynia caused by CFA. The antinociceptive effect produced by MPF4 was reversed with the pre-treatment of animals with naloxone or naltrindole. Oral administration of MPF4 (1.0 mmol/kg, p.o), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.) also produced an anti-allodynic effect. However, none of the compounds evaluated reversed the paw edema produced by CFA. Moreover, MPF4, dipyrone and morphine also produced an anti-allodynic effect in the surgical incisional pain model. The maximal inhibitions obtained with preemptive drug treatment were 66+/-7%, 73+/-9% and 88+/-8% for MPF4 (1.0 mmol/kg, p.o.), dipyrone (1.0 mmol/kg, p.o.) and morphine (0.026 mmol/kg, p.o.), respectively. The maximal inhibitions obtained with curative drug treatment were 53+/-9%, 83+/-7% and 84+/-7%, for MPF4, dipyrone and morphine, respectively. Unlike indomethacin, MPF4 did not induce gastric lesions at the dose that caused the highest antinociception (1.0 mmol/kg, p.o). The anti-allodynic action of MPF4, dipyrone and morphine was not associated with impairment of motor activity.nnnSIGNIFICANCEnThe results of the present study suggest that MPF4 represents a potential target for the development of new drugs to treat persistent inflammatory pain.

Efficient and highly regioselective synthesis of ethyl 1-(2,4-dichlorophenyl)-1H-pyrazole-3-carboxylates under ultrasound irradiation

A series of 14 ethyl 1-(2,4-dichlorophenyl)-1H-pyrazole-3-carboxylates has been synthesized from the cyclocondensation reaction of ethyl 4-methoxy-2-oxoalk[cycloalk]-3-enoates [EtO(2)CC(O)C(R(2))=C(R(1))OR, where R=H, Me; R(1)=Pr, Ph, 4-MeOC(6)H(4), 4-MeC(6)H(4), 4-FC(6)H(4), 4-ClC(6)H(4), 4-BrC(6)H(4), 4-NO(2)C(6)H(4), fur-2-yl; R(2)=H; R(1), R(2)=-(CH(2))(3)-, -(CH(2))(4)-, -(CH(2))(5)-, -(CH(2))(6)-, 3,4-dihydronaphth-2-yl] with 2,4-dichlorophenyl hydrazine hydrochloride under ultrasound irradiation with high regioselectivity and in 71-92% yields. The main goal of this methodology was the significant reduction of reaction times. The compounds were obtained after irradiation for 10-12 min. In addition, the structure of the ethyl 1H-pyrazole-3-carboxylates was supported by crystallographic data.

Microwave-assisted synthesis of 5-trichloromethyl substituted 1-phenyl-1H-pyrazoles and 1,2-dimethylpyrazolium chlorides

Abstract A series of five 5-trichloromethyl-1-phenyl-1 H -pyrazoles and six 5-trichloromethyl-1,2-dimethylpyrazolium chlorides have been synthesized in 80–98% yield by environmentally benign microwave induced techniques involving the cyclocondensation of 4-alkoxy-1,1,1-trichloro-3-alken-2-ones [Cl 3 C(O)C(R 2 )=C(R 1 )OR, where R 2 =H, Me; R 1 =H, alkyl, phenyl and R=Me, Et] with phenyl hydrazine and 1,2-dimethylhydrazine dihydrochloride, respectively, using toluene as solvent. The use of microwave and classical methods are comparable for making pyrazoles, but the formation of pyrazolium chlorides can be achieved in a significant shorter time, and in some cases better yield.

Antioxidant Potential of New Pyrazoline Derivatives to Prevent Oxidative Damage

The antioxidant capacity of a series of six novel synthetic pyrazoline derivatives (i) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-carbaldehyde-pyrazole, (ii) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-acetyl-pyrazole, (iii) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-carboxyamide-pyrazole, (iv) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-benzoyl-pyrazole, (v) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-(2-hydroxybenzoyl)-pyrazole and (vi) 5-hydroxy-3-methyl-5-trifluoromethyl-4,5-dihydro-1H-1-(4-methoxybenzoyl)-pyrazole was evaluated as the capacity of compounds to transfer a hydrogen atom (protection against brain lipid peroxidation and glutathione oxidation) and their capacity to transfer a single electron [ferric-reducing antioxidant power (FRAP) and 1,1-diphenyl-2-picrylhydrazyl radical scavenging (DPPH) assays]. Compound 5 had the highest free radical scavenging capacity in the DPPH assay, while compound 2 had the highest FRAP value (P < 0.05). Only compounds 1, 4 and 5 protected against lipid peroxidation in rat brain homogenate. However, compound 5 was the most effective to prevent basal and iron-, sodium nitroprusside- and H(2)O(2)-stimulated lipid peroxidation (IC(50) < 15 microM) and the only one effective to block glutathione oxidation-mediated by H(2)O(2) (at 150 microM). Our results indicate that compound 5 has the greatest potential to prevent oxidative damage in brain homogenates.

Microwave-assisted synthesis of novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole methyl esters under solvent free conditions

Twelve novel 5-trichloromethyl-4,5-dihydro-1H-1-pyrazole ethyl esters have been synthesized in good yields (70-98%) by using environmentally benign microwave induced techniques. The compounds were synthesized from the cyclocondensation of 1,1,1-trichloro-4-alkoxy-3-alken-2-ones [CCl3C(O)C(R2)=C(R1 )OR, where R, R2 = H, alkyl; R1 = H, alkyl and aryl] with hydrazine methyl carboxylate. The advantages obtained by the using of microwave irradiation under solvent-free conditions, rather than a conventional method, were demonstrated.