A solution of 4-fluorobenzoyl chloride (1.2 mL, 10 mmol) in CH2Cl2 (20 mL) was dropped into a solution of the compound produced in Example 17 (3.31 g, 8.0 mmol) and triethylamine (2.8 mL, 20 mmol) in CH2Cl2 (50 mL) during 30 minutes under cooling with ice. After the solvent was evaporated therefrom in vacuo, water was added to the residue and the mixture was extracted with ethyl acetate. The organic layers were combined, washed with water and a saturated saline solution and dried over anhydrous sodium sulfate. The residual oily product produced by evaporation of the solvent therefrom in vacuo was crystallized from petroleum ether to give the Compound 57 (3.76 g, 94%).
