C[O:2][C:3](=O)[C@@H:4]([CH3:23])[N:5]([P@:13]([CH2:21][CH3:22])([C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:14])CC1C=CC=CC=1.[NH2:25][O:26][K].Cl>>[OH:26][NH:25][C:3](=[O:2])[C@H:4]([NH:5][P@:13]([CH2:21][CH3:22])([C:15]1[CH:20]=[CH:19][CH:18]=[CH:17][CH:16]=1)=[O:14])[CH3:23]N-((S)-Ethylphenylphosphinyl)-N-benzyl-D-alanine methyl ester (105 mg, 0.30 mmol) is treated with a solution of NH2OK (1.0 mL, 1.76M in methanol) prepared as described in Fieser and Fieser, Vol. 1, p. 478. The reaction is stirred for 16 hours at which time TLC indicates completion. The reaction mixture is neutralized with 1M aqueous HCl and the volatiles are removed. The residue is purified by silica gel flash chromatography (95:5 ethyl acetate:methanol) to give N-hydroxy-2(R)-[[(S)-ethylphenylphosphinyl]amino]-propionamide as colorless solid: MS-IS m/z 347 [M+H]+, 369 [M+Na]+.
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