Ethyl (R)-3-((tert-butoxycarbonyl)amino)-4-(2,4,5-trifluorophenyl)butanoate

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid ethyl ester 1e (10 g, 27.7 mmol) and sodium hydroxide (3.32 g, 83.1 mmol) were dissolved in the solvent mixture of 100 mL of methanol and 50 mL of water under stirring. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours, then part of the solution was evaporated under reduced pressure. The residue was added with some water, then pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath. The mixture was extracted with ethyl acetate (200 mL×3), and the combined organic phase was washed with 200 mL of saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (R)-3-tert-butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid if (9.2 g) as a white solid, which was directly used in the next step. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours part of the solution was evaporated under reduced pressure The residue was added with some water pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath The mixture was extracted with ethyl acetate (200 mL×3) the combined organic phase was washed with 200 mL of saturated brine dried over anhydrous sodium sulfate filtered concentrated under reduced pressure recrystallized from ethyl acetate/n-hexane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid ethyl ester 1e (10 g, 27.7 mmol) and sodium hydroxide (3.32 g, 83.1 mmol) were dissolved in the solvent mixture of 100 mL of methanol and 50 mL of water under stirring. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours, then part of the solution was evaporated under reduced pressure. The residue was added with some water, then pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath. The mixture was extracted with ethyl acetate (200 mL×3), and the combined organic phase was washed with 200 mL of saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (R)-3-tert-butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid if (9.2 g) as a white solid, which was directly used in the next step. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours part of the solution was evaporated under reduced pressure The residue was added with some water pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath The mixture was extracted with ethyl acetate (200 mL×3) the combined organic phase was washed with 200 mL of saturated brine dried over anhydrous sodium sulfate filtered concentrated under reduced pressure recrystallized from ethyl acetate/n-hexane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid ethyl ester 1e (10 g, 27.7 mmol) and sodium hydroxide (3.32 g, 83.1 mmol) were dissolved in the solvent mixture of 100 mL of methanol and 50 mL of water under stirring. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours, then part of the solution was evaporated under reduced pressure. The residue was added with some water, then pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath. The mixture was extracted with ethyl acetate (200 mL×3), and the combined organic phase was washed with 200 mL of saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (R)-3-tert-butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid 1f (9.2 g) as a white solid, which was directly used in the next step. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours part of the solution was evaporated under reduced pressure The residue was added with some water pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath The mixture was extracted with ethyl acetate (200 mL×3) the combined organic phase was washed with 200 mL of saturated brine dried over anhydrous sodium sulfate filtered concentrated under reduced pressure recrystallized from ethyl acetate/n-hexane

Conditions: temp:0.00; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: (R)-3-tert-Butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid ethyl ester 1e (10 g, 27.7 mmol) and sodium hydroxide (3.32 g, 83.1 mmol) were dissolved in the solvent mixture of 100 mL of methanol and 50 mL of water under stirring. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours, then part of the solution was evaporated under reduced pressure. The residue was added with some water, then pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath. The mixture was extracted with ethyl acetate (200 mL×3), and the combined organic phase was washed with 200 mL of saturated brine, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure, and then recrystallized from ethyl acetate/n-hexane to obtain the title compound (R)-3-tert-butoxycarbonylamino-4-(2,4,5-trifluoro-phenyl)-butyric acid if (9.2 g) as a white solid, which was directly used in the next step. The reaction mixture was reacted at 40-45° C. for 1-1.5 hours part of the solution was evaporated under reduced pressure The residue was added with some water pH was adjusted to 2-3 with 1 N hydrochloric acid in an ice-water bath The mixture was extracted with ethyl acetate (200 mL×3) the combined organic phase was washed with 200 mL of saturated brine dried over anhydrous sodium sulfate filtered concentrated under reduced pressure recrystallized from ethyl acetate/n-hexane