N,N,N′,N′-Tetramethyl-O-(7-azabenzotriazol-1-yl)uronium hexafluorophosphate (180 mg, 0.46 mmol) was added to a solution of (2S)-2-[(tert-butoxycarbonyl)amino]-3-(4-isopropoxyphenyl)propanoic acid (100 mg, 0.3 mmol) (Example 136, step 2) in N,N-dimethylformamide (5 mL) and N,N-diisopropylethylamine (110 uL, 0.62 mmol). The reaction was stirred for 10 min., and 0.5 M ammonia in 1,4-dioxane (1.2 mL, 0.62 mmol) was added. The reaction was stirred for 1 h. at r.t., and was partitioned between water and ethyl acetate. The organic phase was washed with saturated brine, dried over magnesium sulfate, filtered and concentrated under reduced pressure to give the crude product, (S)-tert-butyl 1-amino-3-(4-isopropoxyphenyl)-1-oxopropan-2-ylcarbamate (90 mg, 90%). Analytical LCMS (M+H-Boc)+: m/z=222.9.
