RESUMEN
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 ß-keto ester and urea or thiourea under microwave 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 µg/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 ß-carotene/linoleic acid assay, some of them exhibiting IC(50) 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 genotoxicity determined by the short-term in vitro chromosomal aberration assay.
Asunto(s)
Antioxidantes/síntesis química , Carbohidratos/síntesis química , Carbohidratos/farmacología , Técnicas de Química Sintética/métodos , Inhibidores de la Colinesterasa/síntesis química , Pirimidinas/química , Tetrazoles/química , Acetilcolinesterasa/metabolismo , Animales , Antioxidantes/química , Antioxidantes/farmacología , Antioxidantes/toxicidad , Carbohidratos/química , Carbohidratos/toxicidad , Bovinos , Línea Celular , Supervivencia Celular/efectos de los fármacos , Inhibidores de la Colinesterasa/química , Inhibidores de la Colinesterasa/farmacología , Inhibidores de la Colinesterasa/toxicidad , Humanos , Ácido Linoleico/química , beta Caroteno/químicaRESUMEN
Cellulose is the most important biopolymer in Nature and is used in preparation of new compounds. Molecular structure of cellulose is a repeating unit of beta-D-glucopyranose molecules forming a linear chain that can have a crystallographic or an amorphous form. Cellulose is insoluble in water, but can dissolve in ionic liquids. Hemicelluloses are the second most abundant polysaccharides in Nature, in which xylan is one of the major constituents of this polymer. There are several sources of cellulose and hemicelluloses, but the most important source is wood. Typical chemical modifications are esterifications and etherifications of hydroxyl groups. TEMPO-mediated oxidation is a good method to promote oxidation of primary hydroxyl groups to aldehyde and carboxylic acids, selectively. Modified cellulose can be used in the pharmaceutical industry as a metal adsorbent. It is used in the preparation of cellulosic fibers and biocomposites such as nanofibrils and as biofuels.
RESUMEN
The study of the acid and neutral parts of the n-hexane extract of Halimium viscosum (S. João da Pesqueira, Portugal) has led to the isolation of various known diterpenoids with the ent-halimane skeleton. Five new compounds have now been isolated, one with the ent-halimane skeleton, and four with the valparane skeleton, two of them with the valparane skeleton degraded. The structures of these compounds, determined by spectroscopic methods using 2D experiments (1H-13C, HMQC and HMBC), were dimethyl 1(10)-halimen-15,18-dioate, dimethyl 3,19-dinor-15-valparen-2,4-dioate, methyl 16-nor-2,3-secovalpara-3,15-dioxo-2-oate, 1,3,5,1 5-valparatetraene and 3R-4alpha-methoxy-15-valparen-2-one.