Sebastião J. de Melo

Synthesis and cytotoxic profile of glycosyl–triazole linked to 1,2,4-oxadiazole moiety at C-5 through a straight-chain carbon and oxygen atoms

The convergent synthesis of an unusual (but simple) class of compounds 5a-g has been achieved by the copper-catalyzed [3+2] cycloaddition reaction of 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl azide 4 with propynyl 3-[3-(aryl)-1,2,4-oxadiazol-5-yl] propionates 3a-g. The formerly known azide 4 has been prepared according to the literature procedure; however, the synthesis of esters 3a-g is being reported for the first time. The infrared as well as (1)H NMR spectra of all new products are in agreement with their proposed structures. By carrying out the nOe experiment of one of the final compounds 5a, we have been able to establish that only the 1,4-regioisomers have been formed in the cycloaddition reaction. All final products presented weak cytotoxic activity, but 5e and 5g had somewhat better behaviour showing 22-25% cell growth inhibition against two cell strains: NCI-H(292) (lung carcinoma) and HEp-2 (larynx carcinoma).

Synthesis of Some 3-Aryl-1,2,4-oxadiazoles Carrying a Protected L-Alanine Side Chain

A sintese de alguns derivados dos 1,2,4-oxadiazois (4a-d) partindo das arilamidoximas apropriadas (1a-d) e do acido N-t-butoxycarbonil-O-benzil-L-aspartico e descrita. As estruturas destes novos compostos foram determinadas por meios espectroscopicos.

Synthesis of new 4-amino-2,6-diarylpyrimidine-5-carbonitriles

A facile synthesis of the title compounds 5a–e, from appropriate amidines and benzylidenemalononitriles, is described.

Pharmacological screening and acute toxicity of bark roots of Guettarda platypoda

Due to its folk use, scientific reports and phytochemical screening, the purpose of this work was to study the phytochemical and the biological properties of the methanol extract and to evaluate the anti-inflammatory activity as well as determine the acute toxicity, antitumor and cytotoxic activity of the root barks of Guettarda platypoda DC., Rubiaceae. In this analysis the presence of flavonoids and therpenoids were identified. These data and the ones in the literature indicated it as a potential antioxidant and motivated the cytotoxic analysis related with three tumoral cell strains as well as to evaluate its antitumoral activity (sarcoma 180 and Ehrlich carcinoma) in female mice. Due to the presence of esteroids and the previous study of the ethanolic extract, its anti-inflammatory activity and toxicity were also evaluated. Absence or low toxicity in 2000 mg/kg doses was verified and the attention to their phytochemical and pharmacological properties is constantly increasing.

Comparative computational studies of 3,4-dihydro-2,6-diaryl-4-oxo-pyrimidine-5-carbonitrile derivatives as potential antinociceptive agents.

In this study, the antinociceptive properties of 3,4-dihydro-2,6-diaryl-4-oxo-pyrimidine-5-carbonitrile derivatives 5a–i at doses of 25 and 50 mg/kg were evaluated in mice, using the abdominal constriction test. Molecular modeling studies were also performed using density functional theory calculations. These data provided information about the electrostatic and ionization potentials and were used to compare the antinociceptive activity of the title compounds. The most active compounds were 3,4-dihydro-2-(4-chlorophenyl)-6-(4-methoxyphenyl)-4-oxo-pyrimidine-5-carbonitrile (5b) and 3,4-dihydro-2,6-diphenyl-4-oxo-pyrimidine-5-carbonitrile (5i), which inhibited the number of abdominal constrictions, at 50 mg/kg dose, in 88.6% and 88% of the sample, respectively. A preliminary SAR study demonstrated that halogen replacement in the phenyl rings of the compounds under study reduces the antinociceptive activity. DFT calculations showed that there is a high correlation between the ionization potentials and the analgesic properties of the compounds. It was found that compounds with a positive ionization potential (compounds 5b and 5i) were found to be the best analgesic drugs in this series.

Synthesis of new 1,2,4-oxadiazoles carrying (1'S,2'S)-t-butyloxycarbonyl-1-amino-2- methyl-1-butyl and (1'S)-t-butyloxycarbonyl-1'-amino-1'-ethyl groups at C-5

A facile and efficient synthesis of 3-aryl-5-[(1S)-t-butyloxycarbonyl-1-amino-(2 S)-methyl-1-butyl)]-1,2,4-oxadiazoles 4a-f and 3-phenyl-5-[(1S)-t-butyloxycarbonyl-1-amino-1-ethyl]-1,2,4 -oxadiazole 6 starting from arylamidoximes, N-t-Boc-L-isoleucine and N-t- Boc-L-alanine is decribed. The structures of the intermediates and final compounds have been deduced from spectroscopic data.

Synthesis of 4-amino-2,6-diaryl-5-cyanopyrimidines as antimicrobial agents

ABSTRACT This article describes an efficient and facile synthesis of 11 2,4,6-trisubstituted 5-cyanopyrimidines starting from meta- and para-substituted 2-cyanocinnamonitriles and arylamidines. The synthesized heterocycles, 3a–k, were characterized by infrared (IR), 1H NMR, 13C NMR, and mass spectral data. The probable mechanism of formation of the title compounds employing 2-cyanocinnamonitriles and arylamidines in the presence of a base was clarified. A preliminary screening of the antibacterial tests clearly showed that 4 out of 11 pyrimidines, 3a, 3e, 3f, and 3k, were effective against bacteria Staphyloccus aureus, Bacillus subtillis, and Pseudomonas aeruginosa. Further, the minimum inhibitory concentration (MIC) against the bacteria has been determined. GRAPHICAL ABSTRACT

Synthesis of Some Unusual (1,2,4‐Oxadiazole)‐Linked Hexenopyranosides and Mannopyranosides

A copper‐catalyzed reaction of propargyl 4,6‐di‐O‐acetyl‐2,3‐dideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside with 3‐(4‐azidophenyl)‐1,2,4‐oxadiazoles gave the corresponding hexenopyranosides bearing an 1,2,4‐oxadiazole subunit in the aglyconic part of the molecule. The same reaction between ethyl 4‐azido‐2,3,4‐trideoxy‐α‐D‐erythro‐hex‐2‐enopyranoside and acetylenic 1,2,4‐oxadiazoles afforded the corresponding hexenopyranosides carrying a triazole and a 1,2,4‐oxadiazole ring at C‐4 of the carbohydrate. Combination of the two sequences gave hexenopyranosides displaying two 1,2,4‐oxadiazole subunits, each one being embedded in the C‐1 and C‐4 frameworks, of the carbohydrate moiety. A simple dihydroxylation reaction of these unsaturated carbohydrates yielded a series of mannopyranosides bearing one or two 1,2,4‐oxadiazole subunits at C‐1 or C‐4. These new compounds were evaluated for their cytotoxic activities against two cell strains: NCI‐H292 (lung carcinoma) and Hep‐2 (larynx carcinoma), some of them presenting impressive cell growth inhibitions.

Use of GC/MS to identify chemical constituents and cytotoxic activity of the leaves of Phoradendron mucronatum and Phoradendron microphyllum (Viscaceae)

Phoradendron mucronatum and P. microphyllum are plants that found in tropical and subtropical areas, used in traditional medicine and popularly known as mistle-thrush. The aim of this study was to identify the chemical constituents of different leaf extracts from P. mucronatum and P. microphyllum and assess cytotoxic activity against strains from a human tumour cells. Extracts obtained with hexane, dichloromethane, chloroform and ethyl acetate from the leaves were analysed by gas chromatography coupled with mass spectrometry (GC-MS) and the cytotoxicity was assessed by the MTT method (bromide (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide)). The tested human tumour cells were NCI-H292 (human pulmonar mucoepidermoid carcinoma), MCF-7 (human breast adenocarcinoma) and HEp-2 (epidermoid carcinoma of the larynx). Analysis by GC/MS of the extracts from leaves of P. microphyllum and P. mucronatum detected 51 different compounds, such as alkaloids, diterpenes, triterpenes, sterols, alcohols, aldehydes, fatty acids and hydrocarbons. In the cytotoxic evaluation, hexane and ethyl acetate extracts from the leaves P. microphyllum inhibited cell growth of NCI-H292 strains (72.97%) and HEp-2 (87.53%), respectively. The extracts of P. mucronatum species showed an inhibitory effect towards NCI-H292 (83.19%/hexane), MCF-7 (88.69%/dichloromethane) and HEp-2 (93.40%/hexane). The extracts showed cytotoxic activity against the tested strains, especially the P. mucronatum, which presented the highest percentages of inhibition of cell growth.

A SIMPLE APPROACH FOR THE SYNTHESIS OF 2,6-DIARYL-4-OXO-3,4-DIHYDROPYRIMIDINE-5-CARBONITRILES

A concise, facile and straightforward synthesis of 2,6-diaryl-4-oxo-3,4-dihydropyrimidine-5carbonitriles 12a-h is reported. The reaction for this preparation involves the condensation of ethyl a cyanocinnamate and its para substituted analogs 8a-e with arylamidines 9a-d under very mild conditions. A probable mechanism of 12a-h from l l a h is proposed. A preliminary pharmacological evaluation of compounds 12c, 12d, 12f e 12h has shown that these compounds possess analgesic activity.