Dichloromethane → N-[N-[(3S)-3-Amino-2-hydroxybutyl]-L-phenylalanvl]-L-leucine, dihydrochloride

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Reaction Steps

To a solution of N-[N-[(3S)-3-[[(t-butyloxy)carbonyl]amino]-2-hydroxybutyl]-L-phenylalanyl-L-leucine, t-butyl ester (faster isomer) (0.33 g, 0.64 mmol) in 3.5 ml of dichloromethane was added trifluoroacetic acid (2 ml). The resulting solution was stoppered and allowed to stand for 1 hour at room temperature, and the solvent was then evaporated. Analysis of the residue by 13C-NMR showed a considerable amount of unreacted t-butyl ester. The recovered material was treated with 10 ml of ~1.5N hydrogen chloride in acetic acid for 1.5 hours at room temperature. The solvent was evaporated (<25° C., vacuum pump) and the residue was triturated with ether yielding a white solid. Analysis by 13C-NMR again revealed t-butyl resonances, although diminished in intensity. The aforementioned hydrogen chloride/acetic acid treatment was repeated three more times, finally yielding 200 mg of the title compound as a white solid, melting point 174°-177° C. (changes form 127°-131° C.).

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