methyl (2S)-3-hydroxy-2-(phenylmethoxycarbonylamino)propanoate

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

Procedure: To a solution of 24.01 g L-serine-methylester hydrochloride in 130 ml of water were added at 0° C. 29.8 g of benzyl chloroformate. The pH was kept at 6-7 by adding a 40% aqueous solution of sodium hydroxide. After 3 h at 0° C. the mixture was extracted with 5 portions of ethyl acetate, the combined extracts were dried and evaporated to give 37.12 g (95%) of pure methyl 3-hydroxy-(S)-2-benzyloxycarbonylamino-propionate. IR (neat): 3380 m (NH, OH), 1720 s, br. (C=O), 1540 s (amide II). After 3 h at 0° C. the mixture was extracted with 5 portions of ethyl acetate the combined extracts were dried evaporated

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

Procedure: N-CBZ-L-serine (25 g) was dissolved in 100 ml of dry N, N-dimethylformamide at 0° C. under argon. Triethylamine (2 e.g., 30 ml) and dimethylsulfate (20 ml) were added. The contents of the vessel were stirred overnight at room temperature and then poured into 500 ml of water and extracted with ethyl acetate (3×200 ml). The organic layer was washed with water and brine and dried with sodium sulfate. Rotary evaporation afforded an oil which crystallized after silica gel chromatography in pure ethyl ether. The structure of the product, N-CBZ-L-serine methyl ester, was confirmed by NMR spectroscopy. extracted with ethyl acetate (3×200 ml) The organic layer was washed with water and brine dried with sodium sulfate Rotary evaporation afforded an oil which crystallized after silica gel chromatography in pure ethyl ether

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

Procedure: Subsequently, to a solution of N-carbobenzyloxy-L-serine methyl ester (4.40 g, 16.7 mmol) in dimethylformamide (210 ml) were added t-butyldiphenylsilyl chloride (5.20 ml, 20.0 mmol) and imidazole (1.36 g, 20.0 mmol) in an ice bath, and the mixture was stirred at room temperature for 3 days. After checking the completion of the reaction, the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution. The organic layer was washed successively with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using n-hexane:ethyl acetate (8:1→6:1) as the eluant to afford t-butyldiphenylsilyloxy-N-carbobenzyloxy-L-serine methyl ester (18.8 g, 99%). the completion of the reaction the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution The organic layer was washed successively with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution dried over anhydrous sodium sulfate filtered concentrated under reduced pressure The residue was purified by chromatography on a silica gel column

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

Procedure: Subsequently, to a solution of N-carbobenzyloxy-L-serine methyl ester (4.40 g, 16.7 mmol) in dimethylformamide (210 ml) were added t-butyldiphenylsilyl chloride (5.20 ml, 20.0 mmol) and imidazole (1.36 g, 20.0 mmol) in an ice bath, and the mixture was stirred at room temperature for 3 days. After checking the completion of the reaction, the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution. The organic layer was washed successively with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution, dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using n-hexane:ethyl acetate (8:1→6:1) as the eluant to afford t-butyldiphenylsilyloxy-N-carbobenzyloxy-L-serine methyl ester (18.8 g, 99%). the completion of the reaction the reaction mixture was partitioned between ethyl acetate and 10% aqueous sodium chloride solution The organic layer was washed successively with saturated aqueous sodium hydrogencarbonate solution and saturated aqueous sodium chloride solution dried over anhydrous sodium sulfate filtered concentrated under reduced pressure The residue was purified by chromatography on a silica gel column

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

Procedure: To a solution of N-carbobenzyloxy-L-serine (4.0 g, 16.7 mmol) in benzene (200 ml) and methanol (50 ml) was added a solution of 2M trimethylsilyldiazomethane in hexane (10.9 ml, 21.7 mmol) in an ice bath, and the mixture was stirred at room temperature for 3 hours. After checking the completion of the reaction, the reaction mixture was concentrated under reduced pressure. The residue was purified by chromatography on a silica gel column using n-hexane:ethyl acetate (1:1→1:3) as the eluant to afford N-carbobenzyloxy-L-serine methyl ester (4.40 g, yield 100%) as a colorless oil. the completion of the reaction the reaction mixture was concentrated under reduced pressure The residue was purified by chromatography on a silica gel column

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

Procedure: N-CBZ-L-serine methyl ester (3.15 g) was dissolved in 40 ml of dichloromethane at 0° C. under argon. Methylenecyclopentane (20 ml) was added, followed by 16 drops of concentrated sulfuric acid. The contents of the vessel were stirred at room temperature overnight then poured into dilute aqueous sodium hydrogen carbonate and extracted with chlorofrom (2×30 ml). The organic layer was dried over sodium sulfate and evaporated. The residual oil was chromatographed on silica gel with 50/50 petroleum ether/diethyl ether to give an oil (78% yield). The product, N-CBZ-O-(1-methylycyclopentyl)-L-serine methyl ester, was confirmed by NMR spectroscopy. extracted with chlorofrom (2×30 ml) The organic layer was dried over sodium sulfate evaporated The residual oil was chromatographed on silica gel with 50/50 petroleum ether/diethyl ether

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

Procedure: N-CBZ-L-serine methyl ester (3.15 g) was dissolved in 40 ml of dichloromethane at 0° C. under argon. Methylenecyclopentane (20 ml) was added, followed by 16 drops of concentrated sulfuric acid. The contents of the vessel were stirred at room temperature overnight then poured into dilute aqueous sodium hydrogen carbonate and extracted with chlorofrom (2×30 ml). The organic layer was dried over sodium sulfate and evaporated. The residual oil was chromatographed on silica gel with 50/50 petroleum ether/diethyl ether to give an oil (78% yield). The product, N-CBZ-O-(1-methylycyclopentyl)-L-serine methyl ester, was confirmed by NMR spectroscopy. extracted with chlorofrom (2×30 ml) The organic layer was dried over sodium sulfate evaporated The residual oil was chromatographed on silica gel with 50/50 petroleum ether/diethyl ether

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

Procedure: N-CBZ-L-serine (25 g) was dissolved in 100 ml of dry N,N-dimethylformamide at 0° C. under argon. Triethylamine (2 e.g., 30 ml) and dimethylsulfate (20 ml) were added. The contents of the vessel were stirred overnight at room temperature and then poured into 500 ml of water and extracted with ethyl acetate (3×200 ml). The organic layer was washed with water and brine and dried with sodium sulfate. Rotary evaporation afforded an oil which crystallized after silica gel chromatography in pure ethyl ether. The structure of the product, N-CBZ-L-serine methyl ester, was confirmed by NMR spectroscopy. extracted with ethyl acetate (3×200 ml) The organic layer was washed with water and brine dried with sodium sulfate Rotary evaporation afforded an oil which crystallized after silica gel chromatography in pure ethyl ether

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

Procedure: The synthesis of indazole amino acid B begins with the iodination of 2,6-dimethylaniline by the action of iodine monochloride (Scheme 3). This intermediate was temporarily set aside. N-CBZ-L-serine methyl ester undergoes a one-pot methanesulfonylation/elimination reaction to afford N-CBZ-dehydroalanine methyl ester. With the iodide and dehydroalanine in hand, they are efficiently coupled using palladium (II) acetate in a Heck coupling to afford the product in 65% yield. At this point, the chiral center is installed using a catalytic asymmetric hydrogenation utilizing (−)-1,2-bis((2R,5R)-2,5-diethylphospholano)benzene(cyclooctadiene)rhodium(I) tetrafluoroborate and hydrogen (60 psi) to give the chiral amino acid in ˜96% ee. The indazole ring is then formed by the action of iso-amyl nitrite. The resulting indazole is highly crystalline. One recrystallization from acetone/hexanes affords the indazole amino acid in excellent purity and with an improved 99.8% ee. Removal of the CBZ protecting group under hydrogenation conditions completes the preparation of fragment B. Indazole amino acid B can also be prepared using enzymatic resolution of the racemic amino acid or keto acid (Hanson, Ronald L.; Davis, Brian L.; Goldberg, Steven L.; Johnston, Robert M.; Parker, William L.; Tully, Thomas P.; Montana, Michael A.; Patel, Ramesh N. Process Research and Development, Bristol-Myers Squibb, New Brunswick, N.J., USA. Organic Process Research & Development (2008), 12(6), 1119-1129.). a one-pot methanesulfonylation/elimination reaction

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

Procedure: To a solution of 24.01 g L-serine-methylester hydrochloride in 130 ml of water were added at 0° C. 29.8 g of benzyl chloroformate. The pH was kept at 6-7 by adding a 40% aqueous solution of sodium hydroxide. After 3 h at 0° C. the mixture was extracted with 5 portions of ethyl acetate, the combined extracts were dried and evaporated to give 37.12 g (95%) of pure methyl 3-hydroxy-(S)-2-benzyloxycarbonylamino-propionate. IR (neat): 3380 m (NH, OH), 1720 s, br. (C=O), 1540 s (amide II). After 3 h at 0° C. the mixture was extracted with 5 portions of ethyl acetate the combined extracts were dried evaporated

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of triphenylphosphine (23.3 g, 0.890 mol) and imidazole (6.0 g, 0.89 mol) in DCM (100 mL) was cooled to 0° C. and iodide (22.6 g, 0.890 mol) was added in small portions over 0.5 h. The cooling bath was removed and the mixture was stirred for 0.5 h. After the mixture was re-cooled to 0° C., a solution of Cbz-L-Ser-OMe 15.0 g, 0.590 mol) in DCM (100 mL) was added dropwise. After the addition, the cooling bath was removed and the mixture was allowed to warm to ambient temperature and stirred for 1.5 h. The mixture was filtered and the filtrate was concentrated to remove most of the solvent. MTBE (400 mL) was added to the residue and the mixture was filtered to remove triphenylphosphine oxide. The filtrate was concentrated and the residue was purified by flash column chromatography on silica gel (petroleum ether/EtOAc=50:1 to 10:1) to afford (R)-methyl 2-(benzyloxycarbonylamino)-3-iodopropanoate (12.3 g, 57% yield) as a colorless solid. The cooling bath was removed After the mixture was re-cooled to 0° C. After the addition the cooling bath was removed to warm to ambient temperature stirred for 1.5 h The mixture was filtered the filtrate was concentrated to remove most of the solvent MTBE (400 mL) was added to the residue the mixture was filtered to remove triphenylphosphine oxide The filtrate was concentrated the residue was purified by flash column chromatography on silica gel (petroleum ether/EtOAc=50:1 to 10:1)

Conditions: temp:0.01; pressure:0.00; stir:; See reaction.notes.procedure_details.

Procedure: A mixture of triphenylphosphine (23.3 g, 0.890 mol) and imidazole (6.0 g, 0.89 mol) in DCM (100 mL) was cooled to 0° C. and iodide (22.6 g, 0.890 mol) was added in small portions over 0.5 h. The cooling bath was removed and the mixture was stirred for 0.5 h. After the mixture was re-cooled to 0° C., a solution of Cbz-L-Ser-OMe 15.0 g, 0.590 mol) in DCM (100 mL) was added dropwise. After the addition, the cooling bath was removed and the mixture was allowed to warm to ambient temperature and stirred for 1.5 h. The mixture was filtered and the filtrate was concentrated to remove most of the solvent. MTBE (400 mL) was added to the residue and the mixture was filtered to remove triphenylphosphine oxide. The filtrate was concentrated and the residue was purified by flash column chromatography on silica gel (petroleum ether/EtOAc=50:1 to 10:1) to afford (R)-methyl 2-(benzyloxycarbonylamino)-3-iodopropanoate (12.3 g, 57% yield) as a colorless solid. The cooling bath was removed After the mixture was re-cooled to 0° C. After the addition the cooling bath was removed to warm to ambient temperature stirred for 1.5 h The mixture was filtered the filtrate was concentrated to remove most of the solvent MTBE (400 mL) was added to the residue the mixture was filtered to remove triphenylphosphine oxide The filtrate was concentrated the residue was purified by flash column chromatography on silica gel (petroleum ether/EtOAc=50:1 to 10:1)