methyl (2R)-2-(cyclopentylamino)butanoate

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

Procedure: Compound II (7.4 g) and cyclopentanone (4.1 g, 49 mmol) were dissolved in 80 mL DCM. After the addition of sodium acetate (4.0 g, 4 mmol) and sodium triacetoxyborohydride (15.0 g, 71 mmol) at 0° C., the mixture was stirred for 12 hr at rt and then 50 mL saturated sodium bicarbonate solution were added. The aqueous phase was extracted with dichloromethane. The combined organic phases were washed with water, dried over MgSO4 and evaporated down to give (R)-methyl 2-(cyclopentylamino)butanoate as a light yellow oil (compound III, 8.6 g, 95% yield). The aqueous phase was extracted with dichloromethane The combined organic phases were washed with water dried over MgSO4 evaporated down

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

Procedure: Compound II (7.4 g) and cyclopentanone (4.1 g, 49 mmol) were dissolved in 80 mL DCM. After the addition of sodium acetate (4.0 g, 4 mmol) and sodium triacetoxyborohydride (15.0 g, 71 mmol) at 0° C., the mixture was stirred for 12 hr at rt and then 50 mL saturated sodium bicarbonate solution were added. The aqueous phase was extracted with dichloromethane. The combined organic phases were washed with water, dried over MgSO4 and evaporated down to give (R)-methyl 2-(cyclopentylamino)butanoate as a light yellow oil (compound III, 8.6 g, 95% yield). The aqueous phase was extracted with dichloromethane The combined organic phases were washed with water dried over MgSO4 evaporated down

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

Procedure: Compound II (7.4 g) and cyclopentanone (4.1 g, 49 mmol) were dissolved in 80 mL DCM. After the addition of sodium acetate (4.0 g, 4 mmol) and sodium triacetoxyborohydride (15.0 g, 71 mmol) at 0° C., the mixture was stirred for 12 hr at rt and then 50 mL saturated sodium bicarbonate solution were added. The aqueous phase was extracted with dichloromethane. The combined organic phases were washed with water, dried over MgSO4 and evaporated down to give (R)-methyl 2-(cyclopentylamino)butanoate as a light yellow oil (compound III, 8.6 g, 95% yield). The aqueous phase was extracted with dichloromethane The combined organic phases were washed with water dried over MgSO4 evaporated down

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Methyl (2R)-2-(cyclopentylamino)butanoate 1k (2.50 g, 13.50 mmol) and sodium bicarbonate (4.54 g, 54 mmol) were dissolved in 100 mL of cyclohexane, stirred for 30 minutes followed by the addition of 2,4-dichloro-5-nitro-pyrimidine (2.88 g, 14.84 mmol), heated to 60° C. and stirred for another 12 hours. The reaction mixture was filtered, washed with dichloromethane (50 mL), and the filtrate was concentrated under reduced pressure, the resulting residue was recrystallized by 150 mL of the mixture solvent of ethyl acetate and n-hexane (V/V=1:4) to obtain the title compound methyl (2R)-2-[(2-chloro-5-nitro-pyrimidin-4-yl)-(1-cyclopentyl)amino]butanoate 1m (3.36 g, yield: 72.6%) as a light yellow solid. stirred for another 12 hours The reaction mixture was filtered washed with dichloromethane (50 mL) the filtrate was concentrated under reduced pressure the resulting residue was recrystallized by 150 mL of the mixture solvent of ethyl acetate and n-hexane (V/V=1:4)

Conditions: temp:60.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: Methyl (2R)-2-(cyclopentylamino)butanoate 1k (2.50 g, 13.50 mmol) and sodium bicarbonate (4.54 g, 54 mmol) were dissolved in 100 mL of cyclohexane, stirred for 30 minutes followed by the addition of 2,4-dichloro-5-nitro-pyrimidine (2.88 g, 14.84 mmol), heated to 60° C. and stirred for another 12 hours. The reaction mixture was filtered, washed with dichloromethane (50 mL), and the filtrate was concentrated under reduced pressure, the resulting residue was recrystallized by 150 mL of the mixture solvent of ethyl acetate and n-hexane (V/V=1:4) to obtain the title compound methyl (2R)-2-[(2-chloro-5-nitro-pyrimidin-4-yl)-(1-cyclopentyl)amino]butanoate 1m (3.36 g, yield: 72.6%) as a light yellow solid. stirred for another 12 hours The reaction mixture was filtered washed with dichloromethane (50 mL) the filtrate was concentrated under reduced pressure the resulting residue was recrystallized by 150 mL of the mixture solvent of ethyl acetate and n-hexane (V/V=1:4)

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

Procedure: The crude compound methyl (2R)-2-aminobutanoate 1j (11.24 g, 0.10 mol) and cyclopentanone (8.24 g, 0.10 mol) were dissolved in 150 mL of dichloromethane, stirred for 1.5 hours followed by the addition of sodium acetate (8.04 g, 0.10 mol) and sodium triacetoxyborohydride (30.52 g, 0.14 mol), and stirred for 3 hours. The reaction solution was poured into 150 mL 10% sodium bicarbonate solution, extracted with dichloromethane (100 mL×3). The combined organic phase was washed with saturated sodium chloride solution (100 mL×3), then dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound methyl (2R)-2-(cyclopentylamino)butanoate 1k (6.04 g, yield: 34.0%) as a light liquid. stirred for 3 hours extracted with dichloromethane (100 mL×3) The combined organic phase was washed with saturated sodium chloride solution (100 mL×3) dried over anhydrous magnesium sulfate filtered the filtrate was concentrated under reduced pressure The resulting residue was purified by silica gel column chromatography

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

Procedure: The crude compound methyl (2R)-2-aminobutanoate 1j (11.24 g, 0.10 mol) and cyclopentanone (8.24 g, 0.10 mol) were dissolved in 150 mL of dichloromethane, stirred for 1.5 hours followed by the addition of sodium acetate (8.04 g, 0.10 mol) and sodium triacetoxyborohydride (30.52 g, 0.14 mol), and stirred for 3 hours. The reaction solution was poured into 150 mL 10% sodium bicarbonate solution, extracted with dichloromethane (100 mL×3). The combined organic phase was washed with saturated sodium chloride solution (100 mL×3), then dried over anhydrous magnesium sulfate, filtered and the filtrate was concentrated under reduced pressure. The resulting residue was purified by silica gel column chromatography to obtain the title compound methyl (2R)-2-(cyclopentylamino)butanoate 1k (6.04 g, yield: 34.0%) as a light liquid. stirred for 3 hours extracted with dichloromethane (100 mL×3) The combined organic phase was washed with saturated sodium chloride solution (100 mL×3) dried over anhydrous magnesium sulfate filtered the filtrate was concentrated under reduced pressure The resulting residue was purified by silica gel column chromatography

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

Procedure: Compound II (7.4 g) and cyclopentanone (4.1 g, 49 mmol) were dissolved in 80 mL DCM. After the addition of sodium acetate (4.0 g, 4 mmol) and sodium triacetoxyborohydride (15.0 g, 71 mmol) at 0° C., the mixture was stirred for 12 hr at rt and then 50 mL saturated sodium bicarbonate solution were added. The aqueous phase was extracted with dichloromethane. The combined organic phases were washed with water, dried over MgSO4 and evaporated down to give (R)-methyl 2-(cyclopentylamino)butanoate as a light yellow oil (compound III, 8.6 g, 95% yield). The aqueous phase was extracted with dichloromethane The combined organic phases were washed with water dried over MgSO4 evaporated down