Browsing by Author "Figueiredo, J.A."
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- Facile synthesis of oxo-/thioxopyrimidines and tetrazoles C–C linked to sugars as novel non-toxic antioxidant acetylcholinesterase inhibitorsPublication . Figueiredo, J.A.; Ismael, M.I.; Pinheiro, J.M.; Silva, A.M.S.; Justino, Jorge; Silva, Filipa V.M.; Goulart, Margarida; Mira, D.; Araújo, M.E.M.; Campoy, R.; Rauter, A.P.Microwave-assisted synthesis of oxo-/thioxopyrimidines and tetrazoles linked to furanoses with D-xylo and D-ribo configuration, and to a D-galacto pyranose is reported and compared to conventional methods. Reaction of dialdofuranoses and dialdopyranoses with a b-keto ester and urea or thiourea under micro wave irradiation at 300 W gave in 10 min the target molecules containing the 2-oxo- or 2-thioxo-pyrimidine ring in high yield. The tetrazole-derived compounds were obtained in two steps by reaction of the formyl group with hydroxylamine hydrochloride, copper sulfate, triethylamine and dicyclohexylcarbodiimide to give an intermediate nitrile, which was then treated with sodium azide. The use of microwave irradiation in the latter step also resulted in a considerably shorter reaction time (10 min) compared to hours under conventional heating to obtain a complete starting materials conversion. Acetylcholinesterase inhibition ranged from 20% to 80% for compounds concentration of 100 lg/mL, demonstrating the potential of this family of compounds for the control of Alzheimer’s disease symptoms. Most of the compounds showed antioxidant activity in the b-carotene/linoleic acid assay, some of them exhibiting IC50 values in the same order of magnitude as those of gallic acid. The bioactive compounds did not show cytotoxic effects to human lymphocytes using the MTT method adapted for non-adherent cells, nor geno toxicity determined by the short-term in vitro chromosomal aberration assay.
- Synthesis of new pseudo‐C‐nucleosides containing pyrazole rings in their structurePublication . Rauter, A. P.; Figueiredo, J.A.; Ismael, M.I.; Justino, JorgeSynthetic approaches to new 4-(furanos-4-C-yl)-1H-pyrazole and 3-(furanos-4-C-yl)-1H-pyrazole derivatives are described, including its pyrazole-5-carboxylate derivative, which is a pyrazofurin analogue. Preparation of related 5-acetoxy-1-acetyl-1H-pyrazole, 5-acetoxy-1H-pyrazole-1-carboxylate, and 4,5-dihydro-1-phenyl-1H-pyrazol-5-one derivatives is also reported. The formation of the pyrazole rings was accomplished either by reaction of enones and of 1,3-diketones with N-nucleophiles or by ring closure of a diazoketone.
- Synthesis of phenylseleno sugars from epoxides and of α,β-unsaturated carbonyl derivatives for the study of their insecticidal activityPublication . Rauter, A.P.; Canda, T.; Justino, Jorge; Ismael, M.I.; Figueiredo, J.A.This work reports the synthesis of sugar epoxides and their derivatives obtained by reaction with the dianion of phenyl selenoacetic acid. Approaches to the introduction of α,β-unsaturated carbonyl units in pyranoid systems were investigated. Preparation of a protected D-glycero-hex-3-enepyranosid-2-ulose and of a D-erythro-hex-2-enono-1,5-lactone is described. Some of the synthesized compounds possess insecticidal activity against fruit flies, house flies, and white flies.