Verdoppelungsreaktionen beim Ringschluss von Peptiden. I. Synthese von Gramicidin S und von bis‐homo‐Gramicidin S aus den Pentapeptid‐Einheiten. 7. Mitteilung über homodet cyclische Polypeptide

Attempts to cyclize the p‐nitrophenyl esters of the pentapeptides L‐valyl‐L‐(Nδ‐tosyl)‐ornithyl‐L‐leucyl‐D‐phenylalanyl‐L‐proline and L‐valyl‐L‐(Nε‐tosyl)‐lysyl‐L‐leucyl‐D‐phenylalanyl‐L‐proline lead to a condensation and cyclization reaction of 2 molecules each of activated esters. The cyclic products are identical with those obtained from the corresponding derivatives of the linear decapeptides. This kind of doubling reaction during cyclization seems to play a greater role in the synthesis of homodetic cyclo‐polypeptides than anticipated. The phenomenon might be expected to occur especially well with peptides containing an odd number of amino acid residues.