RESUMO
A simple and efficient method for regioselective acylation of mangiferin catalyzed by lipase under ultrasound irradiation is reported. Compared with the conventional methods, its main advantages are shorter reaction time and higher yields. The optimum conditions were screened out. Under the optimal conditions (lipase: PCL, acyl donor: vinyl acetate; reaction solvent: DMSO, reaction temperature: 45 degrees C, ultrasonic power: 200 W; substrate ratio: acyl donor/mangiferin 6/1, enzyme loading: 6 mg/ml), the regioselective acylation yield was up to 84%.
Assuntos
Lipase/metabolismo , Lipase/efeitos da radiação , Xantonas/química , Acilação , Catálise , Solventes , Estereoisomerismo , Compostos de Vinila/química , ÁguaRESUMO
The UV-vis spectra of peripherally substituted tetranitrometallophthalocyanines (TNMPcs) 1a-1d and non-peripherally substituted TNMPcs 2a-2d were investigated. In comparison of 1a with 2a, there is the only difference in the substitution position of nitro-groups. The structural diversity of 1a and 2a resulted in different electronic effects of nitro-group on Pc rings, which caused them have two kinds of Q bands. The Q band in the UV-vis spectra of 1a-1d was split into two peaks, which were obviously influenced by temperature, while no split was observed in the Q band of 2a-2d. We can draw a conclusion that tuning nitro-group electronic effect is an important approach for controlling the properties of Pcs.
Assuntos
Indóis/química , Nitrocompostos/química , Eletroquímica/métodos , Isoindóis , Modelos Moleculares , Espectrofotometria , TermodinâmicaRESUMO
The asymmetric esterification of octanoic acid with racemic 2-octanol catalyzed by a lipase from Pseudomonas sp. was investigated in several typical solvents. It was found that the catalytic activity and the enantioselectivity of the enzyme were governed by different physicochemical parameters of the solvent employed. While the former depended on the hydrophobicity (lgP) of the solvent, by contrast the latter was a function of the dielectric constant and the dipole moment. A mechanistic model for the binding site of the enzyme was postulated to rationalize this phenomenon based on the results of the kinetic studies of the reaction in some representative solvents.
