ethyl 5-oxa-6-azaspiro[3.4]octane-7-carboxylate

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

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography

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

Procedure: To a solution of crude 5-oxa-6-aza-spiro[3.4]oct-6-ene-7-carboxylic acid ethyl ester (7.5 g, <40.9 mmol) in tetrahydrofuran (270 mL) at 0° C. was slowly added a solution of borane-dimethyl sulfide complex (10 M in THF, 16.4 mL, 164 mmol). The reaction was allowed to warm to room temperature overnight then recooled to 0° C., and quenched by the careful addition of water. The mixture was diluted with ethyl acetate, washed with water and brine, dried (MgSO4), and concentrated to yield a large amount of white solids. These solids were thoroughly triturated three times with dichloromethane (150 mL). The combined dichloromethane washings were concentrated and the resulting oil was purified by flash chromatography to yield 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.08 g, 29% over 2 steps). 1H-NMR: 400 MHz, (CDCl3) δ: 8.01-7.95 (br, 1H), 4.39-4.28 (m, 2H), 4.18-4.10 (m, 1H), 2.80-2.75 (m, 1H), 2.62-2.49 (m, 2H), 2.37-2.29 (m, 1H), 2.25-2.17 (m, 1H), 2.13-1.95 (m, 1H), 1.88-1.79 (m, 1H), 1.68-1.56 (m, 1H), 1.34 (t, J=7.1 Hz, 3H) ppm. then recooled to 0° C. quenched by the careful addition of water The mixture was diluted with ethyl acetate washed with water and brine dried (MgSO4) concentrated to yield a large amount of white solids These solids were thoroughly triturated three times with dichloromethane (150 mL) The combined dichloromethane washings were concentrated the resulting oil was purified by flash chromatography

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

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography

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

Procedure: To a solution of crude 5-oxa-6-aza-spiro[3.4]oct-6-ene-7-carboxylic acid ethyl ester (7.5 g, <40.9 mmol) in tetrahydrofuran (270 mL) at 0° C. was slowly added a solution of borane-dimethyl sulfide complex (10 M in THF, 16.4 mL, 164 mmol). The reaction was allowed to warm to room temperature overnight then recooled to 0° C., and quenched by the careful addition of water. The mixture was diluted with ethyl acetate, washed with water and brine, dried (MgSO4), and concentrated to yield a large amount of white solids. These solids were thoroughly triturated three times with dichloromethane (150 mL). The combined dichloromethane washings were concentrated and the resulting oil was purified by flash chromatography to yield 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.08 g, 29% over 2 steps). 1H-NMR: 400 MHz, (CDCl3) δ: 8.01-7.95 (br, 1H), 4.39-4.28 (m, 2H), 4.18-4.10 (m, 1H), 2.80-2.75 (m, 1H), 2.62-2.49 (m, 2H), 2.37-2.29 (m, 1H), 2.25-2.17 (m, 1H), 2.13-1.95 (m, 1H), 1.88-1.79 (m, 1H), 1.68-1.56 (m, 1H), 1.34 (t, J=7.1 Hz, 3H) ppm. then recooled to 0° C. quenched by the careful addition of water The mixture was diluted with ethyl acetate washed with water and brine dried (MgSO4) concentrated to yield a large amount of white solids These solids were thoroughly triturated three times with dichloromethane (150 mL) The combined dichloromethane washings were concentrated the resulting oil was purified by flash chromatography

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography

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

Procedure: To a solution of crude 5-oxa-6-aza-spiro[3.4]oct-6-ene-7-carboxylic acid ethyl ester (7.5 g, <40.9 mmol) in tetrahydrofuran (270 mL) at 0° C. was slowly added a solution of borane-dimethyl sulfide complex (10 M in THF, 16.4 mL, 164 mmol). The reaction was allowed to warm to room temperature overnight then recooled to 0° C., and quenched by the careful addition of water. The mixture was diluted with ethyl acetate, washed with water and brine, dried (MgSO4), and concentrated to yield a large amount of white solids. These solids were thoroughly triturated three times with dichloromethane (150 mL). The combined dichloromethane washings were concentrated and the resulting oil was purified by flash chromatography to yield 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.08 g, 29% over 2 steps). 1H-NMR: 400 MHz, (CDCl3) δ: 8.01-7.95 (br, 1H), 4.39-4.28 (m, 2H), 4.18-4.10 (m, 1H), 2.80-2.75 (m, 1H), 2.62-2.49 (m, 2H), 2.37-2.29 (m, 1H), 2.25-2.17 (m, 1H), 2.13-1.95 (m, 1H), 1.88-1.79 (m, 1H), 1.68-1.56 (m, 1H), 1.34 (t, J=7.1 Hz, 3H) ppm. then recooled to 0° C. quenched by the careful addition of water The mixture was diluted with ethyl acetate washed with water and brine dried (MgSO4) concentrated to yield a large amount of white solids These solids were thoroughly triturated three times with dichloromethane (150 mL) The combined dichloromethane washings were concentrated the resulting oil was purified by flash chromatography

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography

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

Procedure: To a solution of crude 5-oxa-6-aza-spiro[3.4]oct-6-ene-7-carboxylic acid ethyl ester (7.5 g, <40.9 mmol) in tetrahydrofuran (270 mL) at 0° C. was slowly added a solution of borane-dimethyl sulfide complex (10 M in THF, 16.4 mL, 164 mmol). The reaction was allowed to warm to room temperature overnight then recooled to 0° C., and quenched by the careful addition of water. The mixture was diluted with ethyl acetate, washed with water and brine, dried (MgSO4), and concentrated to yield a large amount of white solids. These solids were thoroughly triturated three times with dichloromethane (150 mL). The combined dichloromethane washings were concentrated and the resulting oil was purified by flash chromatography to yield 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.08 g, 29% over 2 steps). 1H-NMR: 400 MHz, (CDCl3) δ: 8.01-7.95 (br, 1H), 4.39-4.28 (m, 2H), 4.18-4.10 (m, 1H), 2.80-2.75 (m, 1H), 2.62-2.49 (m, 2H), 2.37-2.29 (m, 1H), 2.25-2.17 (m, 1H), 2.13-1.95 (m, 1H), 1.88-1.79 (m, 1H), 1.68-1.56 (m, 1H), 1.34 (t, J=7.1 Hz, 3H) ppm. then recooled to 0° C. quenched by the careful addition of water The mixture was diluted with ethyl acetate washed with water and brine dried (MgSO4) concentrated to yield a large amount of white solids These solids were thoroughly triturated three times with dichloromethane (150 mL) The combined dichloromethane washings were concentrated the resulting oil was purified by flash chromatography

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

Procedure: To a solution of 2-methoxycarbonylamino-3-methyl-butyric acid (1.11 g, 6.33 mmol) and HATU (2.41 g, 6.34 mmol) in dimethylformamide (13 mL) was added a solution of 5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (980 mg, 5.3 mmol) in dimethylformamide (13 mL). To the resulting reaction mixture was added diisopropylethylamine (1.85 mL, 10.6 mmol) and the reaction was heated to 60° C. for 16 hours. The reaction was diluted with ethyl acetate, washed with water and brine, dried (MgSO4) and concentrated. The resulting residue was purified by flash chromatography to give 6-(2-methoxycarbonylamino-3-methyl-butyryl)-5-oxa-6-aza-spiro[3.4]octane-7-carboxylic acid ethyl ester (1.31 g, 72%). LCMS-ESI+: calculated for C16H26N2O6: 342.18; observed [M+1]+: 342.90. To the resulting reaction mixture washed with water and brine dried (MgSO4) concentrated The resulting residue was purified by flash chromatography