3.5 g (8.6 mmol) of ethyl 7-(N-benzyloxycarbonylamino)-3-hydroxy-2-phenylheptanoate obtained in Example 9 was dissolved in 28 ml of pyridine. 240 mg (1.96 mmol) of dimethylaminopyridine was added to the mixture. The mixture was cooled at 0° C. in an ice bath. 2.5 g (13 mmol) of p-toluenesulfonyl chloride was added for 5 minutes, which was stirred for one hour at a same temperature and further stirred at room temperature for 48 hours. After the consumption of the raw material was confirmed by means of HPLC, 100 ml of ethylacetate was added and 2N hydrochloric acid were further added to the reaction mixture to adjust the pH to 4 to extract. A saturated sodium bicarbonate solution was added to the organic layer prepared to neutralize. The neutralized organic layer was washed with saturated brine and then deied with magnesium sulfate anhydride. After the organic layer was concentrated under reduced pressure, the residue was purified by means of SGIC (eluent: hexane/ethylacetate=3/1) to obtain the target compound as a pale yellow oil in an amount 2.3 g at a yield of 47.6%. The analytical results on the target compound are given below.
