(2,5-dioxopyrrolidin-1-yl) 2-trimethylsilylethyl carbonate

Conditions: temp:0.00; pressure:0.00; stir:

Conditions: temp:0.00; pressure:0.00; stir:

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

Procedure: To a mixture of 1.25 g serine methyl ester hydrochloride, 2.25 ml triethylamine and 10 ml dichloromethane was added at 0° C. a solution of 2.22 g carbonic acid 2,5-dioxo-pyrrolidin-1-yl ester 2-trimethylsilanyl-ethyl ester [R. E. Shute, D. H. Rich, Synthesis, 1987, 346]. After stirring for 24 h at rt the reaction mixture was washed two times with 1N potassium hydrogen sulfate, once with saturated sodium bicarbonate solution and once with brine. The organic phase was dried over magnesium sulfate, filtered and evaporated to give 2.29 g of a colorless liquid. was washed two times with 1N potassium hydrogen sulfate The organic phase was dried over magnesium sulfate filtered evaporated

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

Procedure: To a stirred solution of crude (±)-tert-butyl 3-amino-7-bromo-2,3-dihydrospiro[indene-1,4′-piperidine]-1′-carboxylate (264 mg, 0.69 mmol) in THF (5 mL) was added 10% aq K2CO3 (10 mL), followed by Teoc-OSu (269 mg, 1.04 mmol). The mixture was stirred at rt for 3 d, diluted with ether (80 mL), washed with brine (25 mL) and dried over MgSO4. Removal of the solvent left an oil (240 mg) which was purified chromatography on a 12-g silica cartridge, eluted with a 0-50% EtOAc in hexanes gradient to afford (±)-tert-butyl 7-bromo-3-((2-(trimethylsilyl)ethoxy)carbonylamino)-2,3-dihydrospiro[indene-1,4′-piperidine]-1′-carboxylate (85 mg, 31% for 2 steps). LC-MS Method 1 tR=2.35 min, m/z=425, 427, 547, 549. washed with brine (25 mL) dried over MgSO4 Removal of the solvent left an oil (240 mg) which was purified chromatography on a 12-g silica cartridge eluted with a 0-50% EtOAc in hexanes gradient

Conditions: temp:0.00; pressure:0.00; stir:

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

Procedure: A solution of tert-butyl (2S,3R)-4-(4-cyanobenzylamino)-1-cyclohexyl-3-hydroxybutan-2-ylcarbamate (600 mg, 1.5 mmol) in CH2Cl2 (30 mL) was treated with Teoc-OSu (762 mg, 3.0 mmol, 2.0 equiv) and Et3N (304 mg, 3.0 mmol, 2.0 equiv). The mixture was allowed to stir overnight at rt. LC-MS analysis showed that all of the free amine had been consumed. The solution was washed with water, 1.0 M aq HCl, and brine, then over dried over Na2SO4, filtered and evaporated to leave tert-butyl (2S,3R)-4-(N-(4-cyanobenzyl)-N-(2-(trimethylsilyl)ethoxycarbonyl)amino)-1-cyclohexyl-3-hydroxybutan-2-ylcarbamate. NMR analysis showed that the compound was of sufficient purity to use in the next step. had been consumed The solution was washed with water, 1.0 M aq HCl, and brine over dried over Na2SO4 filtered evaporated

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

Procedure: A solution of tert-butyl (2S,3R)-4-(4-cyanobenzylamino)-1-cyclohexyl-3-hydroxybutan-2-ylcarbamate (600 mg, 1.5 mmol) in CH2Cl2 (30 mL) was treated with Teoc-OSu (762 mg, 3.0 mmol, 2.0 equiv) and Et3N (304 mg, 3.0 mmol, 2.0 equiv). The mixture was allowed to stir overnight at rt. LC-MS analysis showed that all of the free amine had been consumed. The solution was washed with water, 1.0 M aq HCl, and brine, then over dried over Na2SO4, filtered and evaporated to leave tert-butyl (2S,3R)-4-(N-(4-cyanobenzyl)-N-(2-(trimethylsilyl)ethoxycarbonyl)amino)-1-cyclohexyl-3-hydroxybutan-2-ylcarbamate. NMR analysis showed that the compound was of sufficient purity to use in the next step. had been consumed The solution was washed with water, 1.0 M aq HCl, and brine over dried over Na2SO4 filtered evaporated

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

Procedure: A mixture of (R)-2-amino-3-methylbutanoic acid (2.01 g, 17.16 mmol) and 2,5-dioxopyrrolidin-1-yl 2-(trimethylsilyl)ethyl carbonate (4.89 g, 18.87 mmol) in 1:1 dioxane/water (40 mL) was treated with triethylamine (3.59 mL, 25.7 mmol), and the mixture was stirred for two days at room temperature. The mixture was acidified with saturated sodium hydrogen sulfate and extracted 3× with ethyl acetate. The combined organic phases were washed with saturated sodium hydrogen sulfate, water, and brine, then dried over sodium sulfate and concentrated in-vacuo to yield the title compound (4.17 g, 15.96 mmol, 93% yield) as an amber oil. extracted 3× with ethyl acetate The combined organic phases were washed with saturated sodium hydrogen sulfate, water, and brine dried over sodium sulfate concentrated in-vacuo

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

Procedure: A mixture of (R)-2-amino-3-methylbutanoic acid (2.01 g, 17.16 mmol) and 2,5-dioxopyrrolidin-1-yl 2-(trimethylsilyl)ethyl carbonate (4.89 g, 18.87 mmol) in 1:1 dioxane/water (40 mL) was treated with triethylamine (3.59 mL, 25.7 mmol), and the mixture was stirred for two days at room temperature. The mixture was acidified with saturated sodium hydrogen sulfate and extracted 3× with ethyl acetate. The combined organic phases were washed with saturated sodium hydrogen sulfate, water, and brine, then dried over sodium sulfate and concentrated in-vacuo to yield the title compound (4.17 g, 15.96 mmol, 93% yield) as an amber oil. extracted 3× with ethyl acetate The combined organic phases were washed with saturated sodium hydrogen sulfate, water, and brine dried over sodium sulfate concentrated in-vacuo

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

Procedure: To (2S,5R)-5-(benzyloxyamino)piperidine-2-carboxylic acid, dihydrochloride (3.23 g, 10 mmol) described in Example 11 were added 1,4-dioxane (10 mL), water (15 mL) and 5M sodium hydroxide (6 mL), and stirred under ice cooling. Potassium carbonate (1.38 g), N-(trimethylsilylethyloxycarbonyloxy)succinimide (2.85 g) were added further to the mixture, and the temperature was elevated to room temperature, followed by stirring overnight. The mixture was adjusted to pH 4 with citric acid.monohydrate, and extracted with ethyl acetate (50 mL) twice. The organic layer was washed with water and saturated brine and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography (ethyl acetate/hexane=1:1→1:0) to afford 3.41 g of the title compound (yield 86%). was elevated to room temperature by stirring overnight monohydrate, and extracted with ethyl acetate (50 mL) twice The organic layer was washed with water and saturated brine concentrated under reduced pressure

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

Procedure: To (2S,5R)-5-(benzyloxyamino)piperidine-2-carboxylic acid, dihydrochloride (3.23 g, 10 mmol) described in Example 11 were added 1,4-dioxane (10 mL), water (15 mL) and 5M sodium hydroxide (6 mL), and stirred under ice cooling. Potassium carbonate (1.38 g), N-(trimethylsilylethyloxycarbonyloxy)succinimide (2.85 g) were added further to the mixture, and the temperature was elevated to room temperature, followed by stirring overnight. The mixture was adjusted to pH 4 with citric acid.monohydrate, and extracted with ethyl acetate (50 mL) twice. The organic layer was washed with water and saturated brine and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography (ethyl acetate/hexane=1:1→1:0) to afford 3.41 g of the title compound (yield 86%). was elevated to room temperature by stirring overnight monohydrate, and extracted with ethyl acetate (50 mL) twice The organic layer was washed with water and saturated brine concentrated under reduced pressure

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

Procedure: To a solution of 3-(pyrazin-2-yl)-5,6,7,8-tetrahydro-[1,2,4]triazolo[4,3-a]pyrazine (1.0 g, 5.0 mmol) and N,N-diisopropylethylamine (1.7 mL, 9.9 mmol) in DMF (15 mL) was added 1-[2-(trimethylsilyl)ethoxycarbonyloxy]pyrrolidin-2,5-dione (1.5 g, 5.9 mmol). Stirred for 18 h and poured into ice cold brine (150 mL). Precipitate filtered and washed successively with water and ether to afford the desired product as a white solid (1.5 g, 89%). MS (ESI): mass calcd. for C15H22N6O2Si, 346.2; m/z found, 347.2 [M+H]+. 1H NMR (500 MHz, CDCl3) δ 9.50 (d, J=1.4 Hz, 1H), 8.56 (d, J=2.5 Hz, 1H), 8.52-8.48 (m, 1H), 4.91 (s, 2H), 4.60-4.45 (m, 2H), 4.25-4.14 (m, 2H), 3.87 (t, J=5.3 Hz, 2H), 1.07-0.92 (m, 2H), 0.01-0.04 (m, 9H). Precipitate filtered washed successively with water and ether