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

Participants

Reaction Conditions

Reaction Steps

Fmoc-D-Asp(OtBu)-OH (9.0 g) and N,N-diisopropylethylamine (4.6 mL) were added to tetrahydrofuran (100 mL) and cooled to −40° C. Isobutyl chloroformate (3.1 mL) was added, and the solution was gradually warmed to 0° C. over 30 minutes. The solution was cooled to −20° C., and to it was carefully added sodium borohydride (1.64 g, 43 6 mmol) and methanol (10 mL). The solution was gradually warmed to room temperature over two hours, diluted with ethyl acetate (200 mL), washed with water (100 mL) and brine (50 mL), dried with anhydrous magnesium sulfate, filtered, and concentrated to afford crude product of sufficient purity for subsequent use.

Provenance & Evidence