3,4-Methylenedioxyphenyl-2-propanone → (2R,3S)-2-acetoxy-5,5-diethoxy-3-(3,4-methylenedioxyphenyl)pentane

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31.98 g of (2RS,3RS)-5,5-diethoxy-3-(3,4-methylenedioxyphenyl)pentan-2-ol [synthesized by the same method as Reference Example 1(1) and (2) using 3,4-methylenedioxyphenylacetone and iodoacetaldehyde diethyl acetal as the starting materials] was dissolved in 320 ml of vinyl acetate, and 15.1 ml of triethylamine was added thereto. Then, 1.0 g of immobilized lipase (Toyothium LIP) was added thereto, followed by stirring at 30° C. for 16 hours. Further, 0.9 g of immobilized lipase was added thereto, followed by stirring at the same temperature for 46 hours. Then, insoluble matters were filtered off. The filtrate was diluted with ethyl acetate, then sequentially washed with 1N hydrochloric acid, a saturated sodium hydrogencarbonate aqueous solution and a saturated sodium chloride aqueous solution and dried over anhydrous magnesium sulfate. The drying agent was filtered off, and then, the solvent was distilled off under reduced pressure. The residue was purified by silica gel column chromatography (hexane/ethyl acetate=5/1→1/1) to obtain 16.05 g of the above-identified compound, [α]D20 -31.8° (c 1.0, methanol) as colorless oily substance and 18.40 g of (2R,3S)-2-acetoxy-5,5-diethoxy-3-(3,4-methylenedioxyphenyl)pentane as colorless oily substance. Further, the absolute configuration of the above-identified compound was determined by Mosher method (J. Am. Chem. Soc., vol. 113, p. 4092 (1991)).

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