Building Units for N-Backbone Cyclic Peptides. 3. Synthesis of Protected N^α-(ω-Aminoalkyl)amino Acids and N^α-(ω-Carboxyalkyl)amino Acids

An improved synthesis of a family of amino acids that contain ω-aminoalkyl groups and of a new family containing ω-carboxyalkyl groups linked to the α-amine is described. The synthesis was performed by alkylation of suitably monoprotected alkylenediamines and protected ω-amino acids with triflates of α-hydroxy acid esters. The reaction proceeded with inversion of configuration yielding optically pure products. The N^α-(ω-aminoalkyl)amino acids and N^α-(ω-carboxyalkyl)amino acids were orthogonally protected to allow their incorporation into peptides by solid-phase peptide synthesis (SPPS) methodology.