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.