Synthesis and conformational characterization in the solid state of peptides consisting of L ‐phenylalanyl‐ L ‐phenylalanylglycyl and L ‐phenylalanyl‐ L ‐leucylglycyl residues

Two series of peptides containing L ‐phenylalanine, Nps‐( L ‐Phe‐ L ‐Phe‐Gly) n ‐OEt ( n = 1–6) and Nps‐( L ‐Phe‐ L ‐Leu‐Gly) n ‐OEt ( n = 1–7), were prepared by the fragment‐condensation method using the tripeptide N ‐hydroxysuccinimide esters. Conformational characterization of these peptides in the solid state was performed by ir spectroscopy and x‐ray powder diffraction measurement. The peptides Nps‐( L ‐Phe‐ L ‐Phe‐Gly) n ‐OEt take the β‐structure, but the pentadecapeptide and higher peptides of Nps‐( L ‐Phe‐ L ‐Leu‐Gly) n ‐OEt form the α‐helix, although the lower homologs take the β‐structure.