The present invention has for its object to provide a practical method for the purification and isolation on a commercial scale of said compound (1) or compound (2) in good yield and with high quality. The present invention provides a purification/isolation method of a (2S,3S)-1-halo-2-hydroxy-3-N-(tert-butoxycarbonyl)amino-4-phenylbutane (1) or a (2R,3S)-1-halo-2-hydroxy-3-N-(tert-butoxycarbonyl)amino-4-phenylbutane (2) which comprises, for the purpose of removing contaminant impurity from a mixture containing at least one of said compounds (1) and (2), causing the objective compound (1) or compound (2) to be crystallized in the presence of a solvent comprised of a hydrocarbon solvent and then collecting the obtained crystals.