70 mg (1.85 mmol) of sodium borohydride were added to a solution of 207 mg (0.418 mmol) of N-(2-t-butyl-5-carbamoylphenyl)-3-[4-(1-oxobutyl)-2-methoxyphenyl]octanamide (prepared as described in Example 99) in 5 ml of ethanol, and the resulting mixture was stirred for 3.5 hours. At the end of this time, the mixture was ice-cooled, acetone was added to the reaction mixture to decompose any excess of the reagent, and the solvent was removed by distillation under reduced pressure. The resulting residue was mixed with water and then extracted with ethyl acetate. The extract was washed with a saturated aqueous solution of sodium chloride and dried over anhydrous magnesium sulfate. The solvent was then removed by evaporation under reduced pressure. The residue thus obtained was purified by column chromatography through 15 g of silica gel using a gradient elution method, with mixtures of ethyl acetate and methanol ranging from 20:0 to 20:1 by volume as the eluent, to give 203 mg (yield 98%) of the title compound as crystals, melting at 153°-155° C.
