AbstractEsterification reactions were evaluated by using lipases fromRhizomucor miehei (Lipozyme IM20) andPseudomonas cepacia (PS‐30) with equimolar levels (1.77 mmol) of undecanoic acid and glycerol or 1,3‐propanediol (1,3‐PD) or 1,2‐propanediol (1,2‐PD) in organic solvents of log P (partition coefficient between 1‐octanol/water) values of (−0.33–4.5. Reaction yields (percentage of esterified undercanoate) with glycerol ranged from 1.4 to 72%, with greatest yields observed in solvents of log P 4.0–4.5 for Lipozyme, whereas the PS‐30 lipase was similarly effective (27–38% yield) over the full range of solvent polarities. For both enzymes, as solvent apolarity increased, so did the extent of acylation of glycerol in the final product mixture. Reaction yields with 1,3‐PD ranged from 8.1 to 64% for Lipozyme and from 18 to 84% for PS‐30 lipase, with greatest yields observed for both enzymes in solvents of log P values in the range 1.2–5.0. For both lipases, the shift to greater solvent apolarity was accompanied by an increased molar ratio of diacylated‐1,3‐PD/monoacylated‐1,3‐PD in the product mixture. Reaction yields with 1,2‐PD ranged from 2.5 to 45% for Lipozyme and from 12 to 52% for PS‐30 lipase, with greatest yields observed in solvents of log P values in the ranges 1.4–1.9 and 1.4–4.5, respectively. The shift to greater solvent apolarity was accompanied by an increased molar ratio of diacylated‐1,2‐PD: monoacylated‐1,2‐PD in the product mixture, except for Lipozyme in the three most apolar solvents (log P of 3.5–4.5) in which there was a general attenuation of activity. These results suggest the existence of a solvent polarity influence on reaction product selectivity in multiproduct reactions, which can be partially explained on the basis of differential solvation and extraction properties of solvents.
摘要 在对数 P(1-辛醇/水之间的分配系数)值为(-0.33-4.5)的有机溶剂中,使用来自 Rhizomucor miehei(Lipozyme IM20)和 Pseudomonas cepacia(PS-30)的脂肪酶与等摩尔量(1.77 mmol)的十一烷酸和甘油或 1,3-丙二醇(1,3-PD)或 1,2-丙二醇(1,2-PD)进行了酯化反应评估。与甘油的反应产率(酯化的undercanoate的百分比)从1.4%到72%不等,在对数P为4.0-4.5的溶剂中观察到Lipozyme的产率最高,而PS-30脂肪酶在整个溶剂极性范围内的效果相似(产率为27-38%)。对于这两种酶来说,随着溶剂极性的增加,最终产品混合物中甘油的酰化程度也在增加。Lipozyme与1,3-PD的反应产量从8.1%到64%不等,PS-30脂肪酶的反应产量从18%到84%不等,两种酶在对数P值为1.2-5.0的溶剂中的产量最大。对于这两种脂肪酶来说,溶剂极性变大的同时,产品混合物中二乙酰化-1,3-PD/单乙酰化-1,3-PD 的摩尔比也随之增加。Lipozyme 和 PS-30 脂肪酶与 1,2-PD 的反应产率分别为 2.5% 至 45% 和 12% 至 52%,在对数 P 值分别为 1.4-1.9 和 1.4-4.5 的溶剂中观察到的产率最高。随着溶剂极性的增大,产品混合物中二乙酰化-1,2-PD:单乙酰化-1,2-PD 的摩尔比也随之增大,只有 Lipozyme 在三种极性最大的溶剂(log P 值为 3.5-4.5)中的活性普遍减弱。这些结果表明,在多产物反应中,溶剂极性对反应产物的选择性有影响,这可以根据溶剂的溶解和萃取特性的不同得到部分解释。