Dimethyl itaconate (DI), a promising biomass-derived intermediate, cannot be synthesized from itaconic acid (IA) in organisms due to the lack of metabolic pathways. It is necessary to develop a green and high-efficiency method to synthesis DI from IA. In this study, DI was, for the first time, produced from IA in an aqueous medium by an ionic liquid-strengthened enzymatic method. We found that when pretreated by the ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF₆]), the pH tolerance range of the lipase shrunk and the hydrolysis activity of it was greatly inhibited, while its esterification activity was not. Moreover, when the [bmim][PF₆]-treated immobilized Rhizomucor miehei lipase (RML, 50 mg/mL) was employed in a reaction containing IA/methanol at a molar ratio of 1:30 and methanol/water in a volume ratio of 1:10 at 30 °C after 24 h, a 64.3% yield and 73.2% selectivity of DI was obtained. The results of HPLC and GC–MS revealed that in addition to the main product DI, other side products including acetic acid, propionic acid, and itaconic acid cyclolactone were also generated, which indicates that the RML-catalyzed esterification of IA and methanol has various side reactions, such as lactonization and self-decomposition of IA.

中文翻译：

---

离子液体增强固定化根瘤菌米黑脂酶在水性介质中催化衣康酸的催化酯化

衣康酸二甲酯（DI）是一种有前途的生物质衍生中间体，由于缺乏代谢途径，因此无法在生物体中从衣康酸（IA）合成。有必要开发一种绿色高效的方法来从IA合成DI。在这项研究中，DI是首次通过离子液体强化酶法在水性介质中由IA生成的。我们发现，用离子液体1-氟-3-甲基咪唑六氟磷酸盐（[bmim] [PF ₆ ]）预处理时，脂肪酶的pH耐受范围缩小，其水解活性大大降低，同时酯化活性不是。此外，当[bmim] [PF ₆ ]处理的固定化根瘤菌脂肪酶（RML，50 mg / mL）在24小时后于30°C于30°C的反应中使用以1:30的摩尔比的IA /甲醇和以1:10的体积比的甲醇/水的反应得到的DI选择性为73.2％。HPLC和GC-MS的结果表明，除了主要产物DI外，还生成了其他副产物，包括乙酸，丙酸和衣康酸环内酯，这表明RML催化的IA和甲醇的酯化反应有多种副反应，例如内酰胺的内酯化和自分解。