A facile approach for the synthesis of pseudo-peptides incorporating a (2S,3R)-2-amino-cyclopropane carboxylic acid residue.

The synthesis of a pseudo-tripeptide 9 and a pseudo-pentapeptide 1 incorporating the conformationally constrained beta-amino acid (2S,3R)-2-amino cyclopropane carboxylic acid is reported. The key steps of the synthesis are the desymmetrisation of cyclopropane 1,2-dicarboxylic anhydride using (S)-proline t-butyl ester followed by a Curtius rearrangement. Subsequent trapping of the isocyanate with (S)-proline t-butyl ester or HN-(S)-Pro-(S)-Phe-(S)-Phe-OMe gave the desired pseudo-peptides. The stereochemistry of the desymmetrisation reaction was determined by X-ray crystallography of the amido-acid. (C) 1997 Elsevier Science Ltd.