Water → Dihydrocapsiate

8-Methylnonanoic acid (1.65 g, 9.59 mmol), vanillyl alcohol (1.34 g, 8.70 mmol), and lipase PS-C “Amano” I (enzyme immobilized on ceramic: 335 mg) were measured and placed in a flask (25 ml). The mixture in the flask free of a plug was heated with stirring in an oil bath at 45° C. for 37.5 hours. After 2 to 3 hours of stirring with heating, attachment of water on the wall of the upper part of the flask was observed. The flask was returned to room temperature, heptane (10 ml) was added to the reaction mixture, and the mixture was stirred for 10 minutes. The immobilized enzyme and a small amount of precipitated vanillyl alcohol were removed by filtration. The filtrate was concentrated under reduced pressure, and the obtained oil was analyzed by HPLC to find that dihydrocapsiate was contained in 95.7 area %. The mixture was partitioned with heptane (20 ml) and 10% aqueous citric acid solution (20 ml), and the aqueous layer was further extracted with heptane (20 ml). The combined heptane layer was washed with saturated brine (15 ml) and dried over anhydrous magnesium sulfate. Magnesium sulfate was removed by filtration, and the filtrate was concentrated under reduced pressure to give a mixture (2.50 g) of dihydrocapsiate and 8-methylnonanoic acid as a colorless oil. As a result of the analysis, the yield of dihydrocapsiate was 73.1%, and the purity was 99.3 area % by HPLC. The mixture contained 27.4 wt % of 8-methylnonanoic acid relative to dihydrocapsiate.