Distinguishing the topology of macrocyclic compounds and catenanes

The paper explores different possibilities to distinguish macrocyclic oligolactam species with different molecular topologies by ESI mass spectrometry. Collision-induced fragmentation provides unambiguous fragmentation patterns: Monocyclic rings upon single and double protonation predominantly lose water molecules, while catenanes, i.e., two chain-like interlocked macrocycles, undergo ring cleavage followed by loss of a whole ring. At higher collision energies and under multiple collision conditions, a series of different fragments is observed which can be categorized into six different types. These fragments are structure indicative and provide evidence for the connectivities of building blocks within the macrocycles. Gas-phase ion mobility experiments on the other hand result in a good agreement between experimental collision cross-sections and structure predictions from theory. This method does not provide unequivocal differences between monocyclic rings and catenanes due to almost identical cross-sections, but it provides a tool to distinguish between knots (twisted monocyclic rings) and.(untwisted) rings. (C) 2003 Elsevier Science B.V All rights reserved.