| Vitamin E octenylsuccinate was synthesized by the esterification of vitamin E (VE) and octenylsuccinic anhydride (OSA). The reaction was performed by using ethyl acetate as solvents and dimethyl amine pyridine (DMAP) and zinc powder (Zn) as catalysts. The effects of the separation conditions of high performance liquid chromatography (HPLC) on the separation of the reaction products was investigated, and then a optimum HPLC sepatation conditions, including a Dionex Kromasil C18colum and mobile phase of methanol and0.033mol/L phosphoric acid (100/1, v/v) were established. Combination of UV spectra and HPLC-atmospheric pressure chemical ionization (APCI)-mass spectrometry (MS) data, two substances were identified as the isomers of vitamin E octenylsuccinate (VE-OS ester).FTIR and NMR techniques were used for further structure identification and quantitative analysis of VE-OS ester. New absorption peaks at1860cm-1,1776cm-1and1755cm-1were found in the FTIR spectra, suggesting the formation of the structure of the carboxylic acid ester.1H-nuclear magnetic resonance (NMR) spectrum showed the hydroxy group of VE was substituted because of the disappearing of the signal of13-OH. The distribution of H-9signal at3.05ppm and3.20ppm, and four peaks of C-11and C-12at170-180ppm in13C-NMR spectrum, showed that VE-OS ester had two isomers (a and b). The configurations of VE-OS ester were optimized by Density Functional Theory (DFT) B3LYP/6-311++g**, and the results indicated that isomer a is much easier to be formed than isomer b, which agreed well with the analysis data. In addition, the comparison of different high performance liquid chromatography (HPLC) quantitative methods of the VE-OS ester found that measurement of the VE conversion rate was a rapid and accurate method to quantify VE-OS ester, which could be applied in the study on synthesis of VE-OS ester.The synthesis conditions of VE-OS ester were optimized. Effects of the amounts of OSA, catalyst (DMAP, Zn) and slovent, reaction temperature and solvent type on VE conversion rate were investigated. The results showed that the amounts of OSA, DMAP and solvent obviously affect the VE conversion rate. According to the Box-Behnken Design (BBD) center composite design principle, the response surface method experiments of three factors and three levels were designed using VE conversion rate as response value, and the results were analyzed by SAS9.2. The maximum VE conversion rate of100%was obtained when the amounts of OSA, DMAP and solvent were7.85g,0.40g and 61.67mL, respectively. |
