We report the synthesis of 1,3-dioleoyl-2-palmitoylglycerol (OPO) by a three-step method. Vinyl oleate was first synthesized by transvinylation between vinyl acetate and oleic acid. This was further reacted with glycerol at 35 °C for 8 h using 10% (w/v) Novozym 435 to synthesize 1,3-diolein. The 1,3-diolein content in the crude reaction mixture was 90.8% and was obtained at 82.3% (w/w) yield with 98.6% purity after purification. Finally, OPO was chemically synthesized by reacting purified 1,3-diolein with palmitic acid. 94.8% OPO was produced in the crude reaction mixture and the regiopurity of OPO after purification was 98.7% at 90.5% yield based on positional distribution analysis. This is an innovative approach for the synthesis of 1,3-diolein in a solvent-free system as an alternative to previously presented studies that applied solvent system.

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Earlier findings on the nutritional benefits of diacylglycerols (DAGs) have attracted much attention on the synthesis of DAGs. In this study, we reported an improved method for the lipase-catalyzed synthesis of 1,3-diolein by the irreversible glycerolysis of vinyl oleate with glycerol. The effects of reaction system, lipase loading, molar ratio of vinyl oleate to glycerol, reaction temperature and time on 1,3-diolein content in crude reaction mixture were investigated. When the reaction was conducted in a solvent-free system at 30 °C for 8 h by reacting 2 mmol vinyl oleate with 1 mmol glycerol with 8 % (w/w, relative to total reactants) Lipozyme RM IM (Novozymes, Beijing, China) as catalyst, there were 90.5 ± 2.9 % (area/area) 1,3-diolein and (3.3 ± 0.3) % 1,2-diolein produced. After purification, 1,3-diolein was obtained at 81.4 % yield with 98.2 % purity. The lipase-catalyzed synthesis of 1,3-diolein using vinyl oleate as acyl donor by glycerolysis was also conducted using a medium with 50 mmol of glycerol and 100 mmol vinyl oleate. Compared to enzymatic esterification in a solvent, enzymatic glycerolysis for the synthesis 1,3-diolein is more effective due to the irreversible reaction, mild due to the low reaction temperature, and environmentally benign due to the use of solvent-free reaction system.