Building units for N-backbone cyclic peptides .3. Synthesis of protected N-alpha-(omega-aminoalkyl)amino acids and N-alpha-(omega-carboxyalkyl) amino acids

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