Isobutyl chloroformate → tert-butyl (3R)-3-(9H-fluoren-9-ylmethoxycarbonylamino)-4-hydroxy-butanoate

Participants

Reaction Conditions

Reaction Steps

A solution of Fmoc-D-Asp(OtBu)-OH (9.0 g, 21.8 mmol) and N,N-diisopropylethylamine (4.6 mL) in THF (100 mL) at −40° C. was treated with isobutyl chloroformate (3.1 mL, 24.1 mmol), warmed to 0° C. over 30 minutes, cooled to −20° C., and treated slowly with sodium borohydride (1.64 g, 43.6 mmol) and methanol (10 mL). The reaction was gradually warmed to room temperature over 2 hours, diluted with ethyl acetate (200 mL), washed with water (100 mL) and brine (50 mL), dried (MgSO4), filtered, and concentrated to provide the desired product. MS (ESI(+)) m/e 398 (M+H)+.

Provenance & Evidence