benzyl (2S)-3-methoxy-2-[(2-methylpropan-2-yl)oxycarbonylamino]propanoate

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

Procedure: To a solution of the compound of Formula XII(a), (S)-2-tert-butoxycarbonylamino-3-hydroxy-propionic acid benzyl ester (1.7 g, 5.76 mmol) in dichloromethane (50 mL) was added trimethyloxonium tetrafluoroborate (1.11 g, 7.50 mmol), followed by the portion-wise addition of proton sponge (1.61 g, 7.50 mmol). After stirring for 24 hrs at RT, the solution was concentrated, and the residue was dissolved in ethyl acetate, and the solution filtered through a pad of celite. The filtrate was washed with 1 M HCl and brine. The organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Silica-gel flash chromatography with 5% to 15% ethyl acetate in hexanes afforded the compound of Formula XIII(b), (S)-2-tert-butoxycarbonylamino-3-methoxy-propionic acid benzyl ester (1.24 g, 69.6%) as a colorless oil. 1H NMR (300 MHz, CDCl3): δ (ppm) 7.35-7.29 (m, 5H), 4.90-4.87 (m, 1H), 4.51 (s, 2H), 3.92-3.87 (m, 1H), 3.80-3.78 (m, 1H), 3.56 (dd, 2H), 3.42 (dd, 1H), 3.33 (s, 3H), 1.42 (s, 9H). the solution was concentrated the residue was dissolved in ethyl acetate the solution filtered through a pad of celite The filtrate was washed with 1 M HCl and brine The organic layers were dried over MgSO4 filtered concentrated in vacuo

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

Procedure: To a solution of the compound of Formula XII(a), (S)-2-tert-butoxycarbonylamino-3-hydroxy-propionic acid benzyl ester (1.7 g, 5.76 mmol) in dichloromethane (50 mL) was added trimethyloxonium tetrafluoroborate (1.11 g, 7.50 mmol), followed by the portion-wise addition of proton sponge (1.61 g, 7.50 mmol). After stirring for 24 hrs at RT, the solution was concentrated, and the residue was dissolved in ethyl acetate, and the solution filtered through a pad of celite. The filtrate was washed with 1 M HCl and brine. The organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Silica-gel flash chromatography with 5% to 15% ethyl acetate in hexanes afforded the compound of Formula XIII(b), (S)-2-tert-butoxycarbonylamino-3-methoxy-propionic acid benzyl ester (1.24 g, 69.6%) as a colorless oil. 1H NMR (300 MHz, CDCl3): δ (ppm) 7.35-7.29 (m, 5H), 4.90-4.87 (m, 1H), 4.51 (s, 2H), 3.92-3.87 (m, 1H), 3.80-3.78 (m, 1H), 3.56 (dd, 2H), 3.42 (dd, 1H), 3.33 (s, 3H), 1.42 (s, 9H). the solution was concentrated the residue was dissolved in ethyl acetate the solution filtered through a pad of celite The filtrate was washed with 1 M HCl and brine The organic layers were dried over MgSO4 filtered concentrated in vacuo

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

Procedure: To a solution of the compound of Formula XII(a), (S)-2-tert-butoxycarbonylamino-3-hydroxy-propionic acid benzyl ester (1.7 g, 5.76 mmol) in dichloromethane (50 mL) was added trimethyloxonium tetrafluoroborate (1.11 g, 7.50 mmol), followed by the portion-wise addition of proton sponge (1.61 g, 7.50 mmol). After stirring for 24 hrs at RT, the solution was concentrated, and the residue was dissolved in ethyl acetate, and the solution filtered through a pad of celite. The filtrate was washed with 1 M HCl and brine. The organic layers were dried over MgSO4, filtered, and concentrated in vacuo. Silica-gel flash chromatography with 5% to 15% ethyl acetate in hexanes afforded the compound of Formula XIII(b), (S)-2-tert-butoxycarbonylamino-3-methoxy-propionic acid benzyl ester (1.24 g, 69.6%) as a colorless oil. 1H NMR (300 MHz, CDCl3): δ (ppm) 7.35-7.29 (m, 5H), 4.90-4.87 (m, 1H), 4.51 (s, 2H), 3.92-3.87 (m, 1H), 3.80-3.78 (m, 1H), 3.56 (dd, 2H), 3.42 (dd, 1H), 3.33 (s, 3H), 1.42 (s, 9H). the solution was concentrated the residue was dissolved in ethyl acetate the solution filtered through a pad of celite The filtrate was washed with 1 M HCl and brine The organic layers were dried over MgSO4 filtered concentrated in vacuo