Complete Sequence Determination and Localisation of One Imino and Three Sulfide Bridges of the Nonadecapeptide Ro 09–0198 by Homonuclear 2D‐NMR Spectroscopy. The DQF‐RELAYED‐NOESY‐Experiment

The constitution of the nonadecapeptide Ro 09–0198 (1) has been established by homonuclear two‐dimensional NMR spectroscopy. The peptide contains three sulfide bridges and a bridge formed from the side chain of a lysine residue (lysinoalanine moiety). Only the composition was known before, thus the complete sequencing and the elucidation of the bridges had to be performed. Of special importance was the application of the RELAYED‐NOESY experiment. This technique was improved by the introduction of a double‐quantum filter to reduce the tailing around the diagonal. The resulting sequence of 1 exhibits a surprizing analogy of this immunopotentiating peptide to the ACE inhibitor ancovenin.