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To a solution of 16.8 g (77 mmol) of the (5S)-5,6-dihydroxy-3-oxohexanoic tert-butyl ester produced in Example 1 in 120 mL of methylene chloride were added 11.2 mL of pyridine and 10.2 mL of benzoyl chloride at 0° C., and the mixture was stirred at 0° C. for 2 hours. After completion of the reaction, the reaction mixture was diluted with 38 mL of water and adjusted to pH 7 with 20% aqueous NaOH solution. The aqueous layer was separated and further extracted with 2 portions of methylene chloride, 120 mL each. The organic layers were combined and dehydrated over anhydrous sodium sulfate and the solvent was distilled off under reduced pressure to give an oil. This residue was purified by silica gel column chromatography (Kieselgel 60, product of Merck; hexane:acetone=5:1) to give 19.3 g of (5S)-6-benzoyloxy-5-hydroxy-3-oxohexanoic tert-butyl ester (white solid).

1. customAfter completion of the reaction
2. customThe aqueous layer was separated
3. extractionfurther extracted with 2 portions of methylene chloride, 120 mL each
4. distillationthe solvent was distilled off under reduced pressure
5. customto give an oil
6. customThis residue was purified by silica gel column chromatography (Kieselgel 60, product of Merck; hexane:acetone=5:1)