Imidazole → (4R,5S)-5-[(tert-butoxycarbonyl)amino]-4-{[tert-butyl(dimethyl)silyl]oxy}-6-phenyl-2-[4-(2-pyridinyl)benzyl]hexanoic acid

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Reaction Conditions

Reaction Steps

A solution containing the product from Example 107B (10.55 g, 22.35 mmol) in a mixture of dioxane (130 mL) and water (65 mL) was treated with sodium hydroxide solution (33.5 mL, 1N), stirred for 30 minutes at 25° C., concentrated, cooled to 0° C., acidified to pH 5 using 10% citric acid, and partitioned between dichloromethane and water. The organic phase layer was washed with brine, dried over Na2SO4, filtered and concentrated. A solution of the concentrate in dimethylformamide (130 mL) was treated with imidazole (18.3 g, 268.80 mmol) and t-butyldimethylsilyl chloride (20.2 g, 134.01 mmol), stirred at 25° C. for 16 hours, and concentrated. The concentrate was combined with ice and extracted with ethyl acetate. The organic phase was washed with 10% citric acid and brine, dried over MgSO4, filtered, and concentrated. A solution of the residue in a mixture of THF (100 mL), acetic acid (100 mL) and water (33 mL) was stirred at 25° C. for 2 hours, and concentrated under reduced pressure. The residue was dissolved in toluene and concentrated several times, followed by drying under high vacuum to give the title compound, which was used without further purification.

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