Pyridine → tert-butyl(3S)-3-hydroxy-3-{6-[(methylamino)carbonyl]-2-naphthyl}-3-(1-trityl-1H-imidazol-4-yl)propanoate

Participants

Reaction Conditions

Reaction Steps

8 mL of THF and 0.15 mL (1.18 mmol) of chlorotrimethylsilane were added to 1.04 g (16 mmol) of zinc powders, and the mixture was stirred at 35˜40° C. for 5 minutes. A solution of 2.36 mL (16 mmol) of tert-butyl bromoacetate in 20 mL of THF was added dropwise at 45˜52° C. over 10 minutes. The mixture was stirred at 65˜67° C. for 1 hour, and cooled to 25° C. 8.5 mL of THF was added to 1.32 g (4.5 mmol, 1.25 eq) of (+)-cinchonine. The above Reformatsky reagent was added dropwise at 4˜6° C. over 15 minutes. 1.16 mL (14.4 mmol, 4 eq) of pyridine was added dropwise at 5˜7° C. over 2 minutes. The mixture was stirred at 5˜6° C. for 30 minutes. A solution of 1.88 g (3.6 mmol) of N-methyl-6-[(1-trityl-1H-imidazol-4-yl)carbonyl]-2-naphthamide in 15 mL of THF was added dropwise at −44˜−39° C. over 7 minutes. The mixture was stirred at −44˜−35° C. for 5 hours and 20 minutes. 10 mL of 1N hydrochloric acid was added, and the mixture was warmed to 0° C. The mixture was diluted with 50 mL of ethyl acetate, 10 mL of 1N hydrochloric acid was added, and the layers were separated. The organic layer was washed successively with 20 mL of 1N hydrochloric acid 2 times, 20 mL of water, and 20 mL of an aqueous saturated sodium bicarbonate solution. To the organic layer were added 10 mL of 0.1N hydrochloric acid, 10 mL of water and 10 mL of ethyl acetate, and the layers were separated. The organic layer was washed with 20 mL of an aqueous saturated sodium chloride solution, and concentrated at 20° C. or lower under reduced pressure. 10 mL of n-hexane was added to the concentration residue, crystals were loosened, filtered, and washed with 10 mL of n-hexane. Air drying to a constant weight afforded 2.48 g of tert-butyl (3S)-3-hydroxy-3-{6-[(methylamino)carbonyl]-2-naphthyl}-3-(1-trityl-1H-imidazol-4-yl)propanoate (enantiomer excess 95.0% ee).

Provenance & Evidence