H-bonding directed one-step synthesis of novel macrocyclic peptides from ε-aminoquinolinecarboxylic acid

Two macrocyclic peptides 1a and 1b were synthesized directly from epsilon-aminoquinoliiiecarboxylic acid 2a and 2b, respectively. The preorganization of the uncyclized intermediates mediated by hydrogen bonding assisted the cyclization. The structures of 1a and 1b were characterized by H-1 and C-13 NMR spectroscopy and MALDI-TOF MS analysis. Solid state structure of la was investigated by single crystal X-ray studies. Their aggregation behaviors in solution were studied by both variable concentration and temperature H-1 NMR experiments. (C) 2009 Elsevier Ltd. All rights reserved.