methyl (2S)-2-amino-3,3-dimethylbutanoate

Conditions: temp:100.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of (3,3,3-trifluoro-1-nitroprop-1-enyl)cyclohexane (3) (0.62 gm), (S)-methyl 2-amino-3,3-dimethylbutanoate (4) (0.656 gm, 1.3 eq) and diisopropylethylamine (0.69 mL) in toluene (15 mL) was heated to 100° C. for 23 hours. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate, and washed successively with 1N hydrochloric acid, water, brine and then dried over anhydrous sodium sulfate. Evaporation to dryness under reduced pressure gave crude methyl 2-(3-cyclohexyl-1,1,1-trifluoro-3-nitropropan-2-ylamino)-3,3-dimethylbutanoate as a mixture of isomers. Separation by silica gel chromatography, eluting with 8% ethyl acetate/hexane, gave two fractions, a faster eluting compound, 5A-1 (0.553 gm) and a slower eluting compound, 5B-1 (0.3 gm). The two compounds are different diastereoisomers of methyl 2-(3-cyclohexyl-1,1,1-trifluoro-3-nitropropan-2-ylamino)-3,3-dimethylbutanoate (5), although the absolute stereochemistry has not yet been established. After cooling to room temperature washed successively with 1N hydrochloric acid, water, brine dried over anhydrous sodium sulfate Evaporation to dryness under reduced pressure

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

Procedure: A solution of L-t-leucine methyl ester (1.00 g, 6.89 mmol), 6-heptenoic acid (1.06 g, 8.26 mmol), EDC (1.58 g, 8.26 mmol) and HOAt (1.23 g, 8.26 mmol) in DMF (10 mL) was stirred at RT for 2 hours. The reaction mixture was diluted with aqueous saturated NaHCO3 (30 mL), and extracted with EtOAc (3×50 mL). The combined organic layers were washed with water (3×30 mL), brine (20 mL), dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica (5-50% EtOAc/hexane), to give the title compound (1.42 g). LRMS (ESI) m/z 256.3 [(M+H)+; calcd for C14H26NO3: 256.2]. extracted with EtOAc (3×50 mL) The combined organic layers were washed with water (3×30 mL), brine (20 mL) dried over Na2SO4 filtered concentrated The residue was chromatographed on silica (5-50% EtOAc/hexane)

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

Procedure: A solution of L-t-leucine methyl ester (1.00 g, 6.89 mmol), 6-heptenoic acid (1.06 g, 8.26 mmol), EDC (1.58 g, 8.26 mmol) and HOAt (1.23 g, 8.26 mmol) in DMF (10 mL) was stirred at 22° C. for 2 hours. The reaction mixture was diluted with aqueous saturated NaHCO3 (30 mL), and extracted with EtOAc (3×50 mL). The combined organic layers were washed with water (3×30 mL), brine (20 mL), dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica gel, eluting with 5-50% EtOAc/hexane, to give the title product (1.42 g, 81%). LRMS (ESI) m/z 256.3 [(M+H)+; calcd for C14H26NO3: 256.2]. extracted with EtOAc (3×50 mL) The combined organic layers were washed with water (3×30 mL), brine (20 mL) dried over Na2SO4 filtered concentrated The residue was chromatographed on silica gel eluting with 5-50% EtOAc/hexane

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

Procedure: A solution of L-tert-leucine methyl ester (1.00 g, 6.89 mmol), 6-heptenoic acid (1.06 g, 8.26 mmol), EDC (1.58 g, 8.26 mmol) and HOAt (1.23 g, 8.26 mmol) in DMF (10 mL) was stirred at 22° C. for 2 hours. The reaction mixture was diluted with aqueous saturated NaHCO3 (30 mL), and extracted with EtOAc (3×50 mL). The combined organic layers were washed with water (3×30 mL), brine (20 mL), dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica gel, eluting with 5-50% EtOAc/hexane, to give the title product (1.42 g, 81%). LRMS (ESI) m/z 256.3 [(M+H)+; calcd for C14H26NO3: 256.2]. extracted with EtOAc (3×50 mL) The combined organic layers were washed with water (3×30 mL), brine (20 mL) dried over Na2SO4 filtered concentrated The residue was chromatographed on silica gel eluting with 5-50% EtOAc/hexane

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

Procedure: A solution (0.39 M) of methyl 3-methyl-L-valinate in a 2:1 mixture of saturated aqueous NaHCO3 and CH2Cl2 was cooled in an ice bath and stirred rapidly. The mixture was treated with triphosgene (0.45 eq) in one portion, and the resulting mixture was stirred for 0.5 h. The reaction was diluted with CH2Cl2, and the layers were separated. The aqueous phase was extracted with CH2Cl2, then the combined organics were washed with brine and dried. Removal of the solvent gave the title compound as clear oil that was kept for 12 h under vacuum (0.1 mbar) then used directly in the subsequent step. 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 3.75 (s, 1H), 1.00 (s, 9H). was cooled in an ice bath the resulting mixture was stirred for 0.5 h the layers were separated The aqueous phase was extracted with CH2Cl2 the combined organics were washed with brine dried Removal of the solvent

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

Procedure: A solution (0.39 M) of methyl 3-methyl-L-valinate in a 2:1 mixture of saturated aqueous NaHCO3 and CH2Cl2 was cooled in an ice bath and stirred rapidly. The mixture was treated with triphosgene (0.45 eq) in one portion, and the resulting mixture was stirred for 0.5 h. The reaction was diluted with CH2Cl2, and the layers were separated. The aqueous phase was extracted with CH2Cl2, then the combined organics were washed with brine and dried. Removal of the solvent gave the title compound as clear oil that was kept for 12 h under vacuum (0.1 mbar) then used directly in the subsequent step. 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 3.75 (s, 1H), 1.00 (s, 9H). was cooled in an ice bath the resulting mixture was stirred for 0.5 h the layers were separated The aqueous phase was extracted with CH2Cl2 the combined organics were washed with brine dried Removal of the solvent

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

Procedure: A solution (0.39 M) of methyl 3-methyl-L-valinate in a 2:1 mixture of saturated aqueous NaHCO3 and CH2Cl2 was cooled in an ice bath and stirred rapidly. The mixture was treated with triphosgene (0.45 eq) in one portion, and the resulting mixture was stirred for 0.5 h. The reaction was diluted with CH2Cl2, and the layers were separated. The aqueous phase was extracted with CH2Cl2, then the combined organics were washed with brine and dried. Removal of the solvent gave the title compound as clear oil that was kept for 12 h under vacuum (0.1 mbar) then used directly in the subsequent step. 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 3.75 (s, 1H), 1.00 (s, 9H). was cooled in an ice bath the resulting mixture was stirred for 0.5 h the layers were separated The aqueous phase was extracted with CH2Cl2 the combined organics were washed with brine dried Removal of the solvent

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

Procedure: A solution (0.39 M) of methyl 3-methyl-L-valinate in a 2:1 mixture of saturated aqueous NaHCO3 and CH2Cl2 was cooled in an ice bath and stirred rapidly. The mixture was treated with triphosgene (0.45 eq) in one portion, and the resulting mixture was stirred for 0.5 h. The reaction was diluted with CH2Cl2, and the layers were separated. The aqueous phase was extracted with CH2Cl2, then the combined organics were washed with brine and dried. Removal of the solvent gave the title compound as clear oil that was kept for 12 h under vacuum (0.1 mbar) then used directly in the subsequent step. 1H NMR (400 MHz, CDCl3) δ 3.79 (s, 3H), 3.75 (s, 1H), 1.00 (s, 9H). was cooled in an ice bath the resulting mixture was stirred for 0.5 h the layers were separated The aqueous phase was extracted with CH2Cl2 the combined organics were washed with brine dried Removal of the solvent

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

Procedure: To a solution of 7-(tert-butoxycarbonyl)-3-phenyl-5,6,7,8-tetrahydroimidazo[1,5-a]pyrazine-1-carboxylic acid (Intermediate 3B) (2.0 g, 5.82 mmol) in DMF was added (S)-methyl 2-amino-3,3-dimethylbutanoate (1.18 g, 8.15 mmol), followed by DIEA (2.26 g, 17.47 mmol). The resulting mixture was stirred for 20 min and TBTU (2.43 g, 7.57 mmol) was added and the mixture was stirred overnight. The reaction mixture was diluted with water and extracted with EtOAc, washed with water, brine, dried over anhydrous Na2SO4, filtered and concentrated. The residue was purified by flash chromatography eluting with ethyl acetate/hexanes 10-50% gradient to give Intermediate 22A 2.73 g (98%). LCMS (+ESI) m/z 470.0 [M+H]+. the mixture was stirred overnight extracted with EtOAc washed with water, brine dried over anhydrous Na2SO4 filtered concentrated The residue was purified by flash chromatography eluting with ethyl acetate/hexanes 10-50% gradient

Conditions: temp:100.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of (3,3,3-trifluoro-1-nitroprop-1-enyl)cyclohexane (3) (0.62 gm), (S)-methyl 2-amino-3,3-dimethylbutanoate (4) (0.656 gm, 1.3 eq) and diisopropylethylamine (0.69 mL) in toluene (15 mL) was heated to 100° C. for 23 hours. After cooling to room temperature, the reaction mixture was diluted with ethyl acetate, and washed successively with 1N hydrochloric acid, water, brine and then dried over anhydrous sodium sulfate. Evaporation to dryness under reduced pressure gave crude methyl 2-(3-cyclohexyl-1,1,1-trifluoro-3-nitropropan-2-ylamino)-3,3-dimethylbutanoate as a mixture of isomers. Separation by silica gel chromatography, eluting with 8% ethyl acetate/hexane, gave two fractions, a faster eluting compound, 5A-1 (0.553 gm) and a slower eluting compound, 5B-1 (0.3 gm). The two compounds are different diastereoisomers of methyl 2-(3-cyclohexyl-1,1,1-trifluoro-3-nitropropan-2-ylamino)-3,3-dimethylbutanoate (5), although the absolute stereochemistry has not yet been established. After cooling to room temperature washed successively with 1N hydrochloric acid, water, brine dried over anhydrous sodium sulfate Evaporation to dryness under reduced pressure

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

Procedure: A solution of L-t-leucine methyl ester (1.00 g, 6.89 mmol), 6-heptenoic acid (1.06 g, 8.26 mmol), EDC (1.58 g, 8.26 mmol) and HOAt (1.23 g, 8.26 mmol) in DMF (10 mL) was stirred at RT for 2 hours. The reaction mixture was diluted with aqueous saturated NaHCO3 (30 mL), and extracted with EtOAc (3×50 mL). The combined organic layers were washed with water (3×30 mL), brine (20 mL), dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica (5-50% EtOAc/hexane), to give the title compound (1.42 g). LRMS (ESI) m/z 256.3 [(M+H)+; calcd for C14H26NO3: 256.2]. extracted with EtOAc (3×50 mL) The combined organic layers were washed with water (3×30 mL), brine (20 mL) dried over Na2SO4 filtered concentrated The residue was chromatographed on silica (5-50% EtOAc/hexane)

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

Procedure: A solution of L-t-leucine methyl ester (1.00 g, 6.89 mmol), 6-heptenoic acid (1.06 g, 8.26 mmol), EDC (1.58 g, 8.26 mmol) and HOAt (1.23 g, 8.26 mmol) in DMF (10 mL) was stirred at 22° C. for 2 hours. The reaction mixture was diluted with aqueous saturated NaHCO3 (30 mL), and extracted with EtOAc (3×50 mL). The combined organic layers were washed with water (3×30 mL), brine (20 mL), dried over Na2SO4, filtered and concentrated. The residue was chromatographed on silica gel, eluting with 5-50% EtOAc/hexane, to give the title product (1.42 g, 81%). LRMS (ESI) m/z 256.3 [(M+H)+; calcd for C14H26NO3: 256.2]. extracted with EtOAc (3×50 mL) The combined organic layers were washed with water (3×30 mL), brine (20 mL) dried over Na2SO4 filtered concentrated The residue was chromatographed on silica gel eluting with 5-50% EtOAc/hexane