ORTHOGONALLY PROTECTED N3-(CARBOXYMETHYL)-L-2,3-DIAMINOPROPANOIC ACIDS AND O-(CARBOXYMETHYL)-L-SERINES FOR SOLID-PHASE PEPTIDE-SYNTHESIS

The syntheses of the orthogonally protected N3-(carboxymethyl)-2,3-L-diaminopropanoic acids 18, 19, and 20 and O-(carboxymethyl)-L-serines 35 and 38 are described. All of the diaminopropanoic acids were prepared via reductive amination of the known oxazolidine aldehyde 9. The carboxymethyl serines were prepared via 0-alkylation of N-CBZ-L-serine. To enable incorporation of these amino acids into cyclic peptides, protecting group schemes were designed for compatibility with either Boc or Fmoc solid-phase peptide synthesis.