To the compound of formula (9) (261.25 g, 0.79 mol) obtained by concentration under reduced pressure in Example 2 (it was assumed that the compound of formula (9) was obtained in a yield of 79% starting from Example 1, since the peak area by HPLC was 78.54%) were added NMP [1050 ml, 4 ml/g with respect to the compound of formula (9)] and DBMP (307 g, 1.2 mol). To the reaction mixture was added LTB (107 g, 1.3 mol), which was then stirred under the condition of not exceeding 45° C. After about 6˜19 hours, completion of the reaction was confirmed by HPLC, and 14% aqueous NH4Cl solution [1830 ml, 7 ml/g with respect to the compound of formula (9)] was added thereto to stop the reaction. MTBE [first: 1050 ml, 4 ml/g with respect to the compound of formula (9); second: 520 ml, 2 ml/g with respect to the compound of formula (9)] was added thereto twice for phase-separation. Thus obtained organic layers were combined and washed with 21% aqueous NaCl solution [1650 ml, 6.3 ml/g with respect to the compound of formula (9)]. The remaining organic layer was concentrated under reduced pressure, and heptane [1300 ml, 5 ml/g with respect to the compound of formula (8)] was added thereto. The mixture was cooled to −10° C., and filtered after about 3 hours to give the title compound of formula (10) (586 g, Purity 96.23%, Yield 71.3%) as a solid.
