To a mixture of the compound (5.09 g) obtained in Example 417d, nickel (II) chloride hexahydrate (61 mg) and methanol (130 ml), sodium borohydride (1.46 g) was added. The reaction mixture was stirred at room temperature for 20 min and, after addition of 2 N HCl, adjusted to pH 8 with a saturated aqueous sodium hydrogencarbonate solution and then concentrated under reduced pressure. To the resulting residue, water was added and the mixture was subjected to extraction with ethyl acetate. The organic layer was washed with a saturated aqueous sodium chloride solution, dried with anhydrous sodium sulfate and concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography (eluent, ethyl acetate:n-hexane=1:4) to give the titled compound (yield, 85%).
