RESUMEN
α-exo-Methylene-γ-butyrolactones and α-exo-methylene-δ-valerolactones constitute an important group of natural and bioactive products. A simple and general protocol of halolactonization of dienoic acids to obtain various α-exo-methylene-lactones in excellent yields is described. The resulting halogenated α-exo-methylene-lactones were found to exhibit potent cytotoxic activities.
Asunto(s)
Antineoplásicos/farmacología , Lactonas/farmacología , Antineoplásicos/síntesis química , Antineoplásicos/química , Línea Celular Tumoral , Proliferación Celular/efectos de los fármacos , Relación Dosis-Respuesta a Droga , Ensayos de Selección de Medicamentos Antitumorales , Halogenación , Humanos , Lactonas/síntesis química , Lactonas/química , Estructura Molecular , Relación Estructura-ActividadRESUMEN
The strained olefins in trans-cyclooctenes serve as efficient catalysts for halolactonizations, including bromolactonizations and iodolactonizations. The trans-cyclooctene framework is essential for excellent catalytic performance, and the substituents also play important roles in determining efficiency. These results are the first demonstration of catalysis by a trans-cyclooctene.
RESUMEN
Halolactones are used both in chemical synthesis as intermediates as well as in various industries. These compounds may be secondary metabolites of living organisms, although they are mainly obtained by chemical synthesis. The substrates for the synthesis of chloro-, bromo- and iodolactones are often unsaturated carboxylic acids, and sometimes they are unsaturated esters. The article presents a number of different methods for the production of halolactones, both racemic mixtures and enantiomerically enriched compounds.
RESUMEN
Phase-vanishing reactions are triphasic reactions which involve a reagent, a liquid perfluoroalkane as a phase screen and a substrate. The perfluoroalkane does not dissolve any of the reactants and is used to separate them. Halolactonization of neat substrates under phase-vanishing conditions avoids use of both solvents and basic reaction conditions. Both gamma,delta-alkenoic acids as well as the corresponding methyl esters are suitable substrates for phase-vanishing halolactonizations. The reaction works well both on solid and liquid substrates and the products are obtained in good to excellent yields, particularly in the case of rigid bicyclic systems. Bromine (Br(2)) and iodine monochloride (ICl) are suitable electrophiles for bromolactonization and iodolactonization, respectively. Although in some cases iodine gave satisfactory yields of the corresponding iodolactone, it is generally inferior to iodine monochloride.