13C NMR Spectroscopic Control of the Synthesis of Alamethicin F 30 and its Segments

All segments built up for the total synthesis of the α‐helical antibiotic alamethicin F 30 (1) were investigated by 13C NMR spectroscopy of methanolic solutions. With a few exceptions the signals were unequivocally assignable by comparison with spectra of related peptides, by coupled spectra and J‐modulated spin‐echo experiments. For the first time a synthetic and highly pure alamethicin F 30 preparation could be studied by 13C NMR spectroscopy at 100.6 MHz. All results were in full agreement with the synthesized intermediates and the final product, and with their conformations as derived from circular dichroism and X‐ray analysis. Partially there is a striking retention of conformation from smaller to larger segments.