反应详情

A solution of (S)-1-tert-butyl 5-ethyl 2-(bis(tert-butoxycarbonyl)amino)pentanedioate (1.7 g, 3.93 mmol) in dry tetrahydrofuran (30 mL) was cooled to −78° C. with acetone/dry ice bath and added diisobutylaluminum hydride (1.0 M in hexanes 5.9 mL, 5.90 mmol) dropwise over the period of 5 minutes. The reaction was complete after stirring for four hours, then quenched with water (1.5 mL) and allowed to warm to room temperature by removing the external cold bath. The resulting white thick solution was filtered through celite powder and washed with diethyl ether (200 mL). The filtrate was concentrated under reduced pressure and purified on 40 g silica gel column (eluent hexanes to 20% ethyl acetate in hexanes) to afford (S)-tert-butyl 2-(bis(tert-butoxycarbonyl)amino)-5-oxopentanoate (0.90 g, 59.1% yield) as a thick oil. 1H NMR (CDCl3) δ ppm: 9.79 (s, 1H), 4.77 (dd, J=9.3, 5.2 Hz, 1H), 2.52 (m, 3H), 2.16 (m, 1H), 1.52 (s, 18H), 1.47 (s, 9H). 13C NMR (CDCl3) δ ppm: 201.2, 169.2, 152.4, 83.1, 81.5, 58.11, 40.7, 28.0, 27.9 and 21.9. MS (ESI+): 410 (M+Na)+.

1. customquenched with water (1.5 mL)
2. customby removing the external cold bath
3. filtrationThe resulting white thick solution was filtered through celite powder
4. washwashed with diethyl ether (200 mL)
5. concentrationThe filtrate was concentrated under reduced pressure
6. custompurified on 40 g silica gel column (eluent hexanes to 20% ethyl acetate in hexanes)