European Journal of Organic Chemistry
© WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Inverse γ-Turn-Inspired Peptide: Synthesis and Analysis of Segetalin A Indole Hemiaminal (Eur. J. Org. Chem. 34/2015)
The cover picture shows the reversible cyclization of a peptide aldehyde, which is based on the cyclic hexapeptide Segetalin A. The traffic light symbolizes the formation of the species involved in this reaction. The substitution of a peptide bond for an imine transforms the irreversible macrocyclization of peptides into a reversible process. The inherent cyclization tendency of a linear peptide is then analyzable through the equilibrium between aldehyde and imine by virtue of the higher reactivity of the corresponding linear peptide aldehyde. The tryptophan side chain of Segetalin A aldehyde forms a 12-membered cyclic indole hemiaminal instead of the 18-membered macrocyclic imine expected. In this article on 7443 ff, A. Geyer et al. analyze this uncommon hemiaminal, which shows that the biosynthesis of cyclic peptides is not necessarily based on linear precursor peptides with a high inherent macrolactamization tendency.