Dicyclohexylcarbodiimide → Ritonavir

Participants

Reaction Steps

To a solution of the product of Example 70 (9.1 g, 21.4 mmol), HOBT (3.6 g, 23.5 mmol) and N-((N-Methyl-N-((2-isopropyl-4-thiazolyl)methyl)amino)-carbonyl)-L-valine (7.37 g, 23.5 mmol) in THF (170 mL) was added DCC (4.85 g, 23.5 mmol). The solution was stirred at ambient temperature for 16 hours (DCU precipitates). THF was removed under vacuum and the resulting paste was stirred with cold 1N HCl (106 mL at 5° C.) for 3 hours to dissolve the the crude product. The DCU was removed by filtration and the filter cake was washed with 1N HCl (30 mL). KH2PO4 (3.2 g) was dissolved in the combined HCl filtrates. The solution was mixed with ethyl acetate (80 mL) and neutralized to pH 7 with aqueous NaOH (60.3 g of 10% w/w NaOH). The aqueous layer was extracted with another 25 mL ethyl acetate and the combined ethyl acetate extracts were washed with aqueous NaHCO3 (2×37 mL of 5% w/w NaHCO3). The organic layer was dried with Na2SO4 (13 g), filtered, and concentrated under vacuum at ≤45° C. The residue was dissolved in a 1:1 ethyl acetate/heptane mixture (200 mL) at 70° C. The solution was allowed to cool slowly and stirred overnight at room temperature to provide a thick slurry. The product was collected by filtration and washed with 1:1 ethyl acetate/heptane (20 mL). The product was dried briefly at 55° C. in a vacuum oven to obtain an approximate weight prior to the second crystallization (12.85 g, 83%). A second crystallization from 144 mL of 2:1 ethyl acetate/heptane (dissolved at ~70° C., then stirred at room temperature 12 hours) produced a thick slurry of fine white solid. The product was collected by filtration and washed with 15 mL 2:1 ethyl acetate/heptane, then dried in a vacuum oven at 55° C. for 2 days to give the desired product. Yield 11.9 g (77%).

Provenance & Evidence