| In the last decade, LC-MS has become the method of choice for the rapid analysis of small organic molecules, peptides in particular. In addition to the development of novel routes towards unusual amino acids, the Amsterdam Biomolecular Synthesis group embarked on cyclic peptide synthesis. Cyclopeptides are ubiquitously present in nature and highly bioactive members have been reported. Especially small cyclic peptides (4-6 amino acid residues) could serve as excellent lead candidates for drug research. Extensive research, however, is hampered by the difficult lactamization step. Over the years, the Amsterdam synthesis group has developed new methods to achieve difficult lactamizations based on ring-contraction or pseudo high-dilution strategies. Also, we have shown that replacement of backbone amide bonds by bioisosteric 1,2,3-triazoles greatly facilitates the cyclization efficiency. Currently, besides ongoing efforts to optimize our methodologies, these methods are applied for the synthesis of several pharmacologically relevant cyclic peptides. The greatest bottleneck in this research is the analysis of reaction mixtures and isolated products. The high polarity of the products and intermediates prevent the use of traditional straight phase chromatographic techniques. Also, the NMR spectra of the peptides involved in the product are highly complex. To date, RPLC-MS (reversed-phase liquid chromatography mass spectrometry) is the technique of choice in peptide research. The information that is obtained by LC-MS analysis is vital to the optimization of synthetic procedures and is essential for a clear-cut confirmation of the structure of newly synthesized cyclic peptides and linear precursors. Therefore, we request funding to acquire a state of the art LC-MS apparatus. The selected instrument also allows for the performing MS-MS experiments in order to ascertain the connectivity of the cyclic peptides and distinguished cyclic structures from possible linear peptides that are isobaric with the cyclic species. |
