Cross-ring cleavage

Another characteristic of the CID behavior of hthium containing cationized loganic acid is the retro Diels-Alder (RDA) reaction that affords several possible fragmentation products. These so-called cross ring cleavages are very useful iu the stracture determiua-tion of various compounds and are typically present in the CID spectra of alkah cationized ions of several groups of compounds (Schemes 7 and 8) . ... 

Cross-ring cleavage to form alkene and carbonyl fragments is the predominate type of fragmentation for oxetanes. The charge may reside on either fragment, as shown for oxetane (equation 1). 

The MS fragmentation of 2-oxetanones has received relatively little attention. 2-Oxetanone is reported to give both modes of cross-ring cleavage, as well as a hydrogen-... 

Perform glycosidic cleavage Prjmary fragments Perform cross-ring cleavage... 

The formation of diethylenetriamine A -glycoside complexes suppressed the loss of siahc acid in MS-MS. Therefore, hnkage information could be obtained via cross-ring cleavages. 

Figure 6 The most commonly observed cross-ring cleavage ions with the proposed mechanism for their formation. The subscript denotes that the cleavages occur at the reducing end (A ions) or nonreducing end (X ions) of the nth residue from either end. Other cleavages are possible and can be named accordingly but their mechanistic basis is less clear.

Linkage Analysis from a CID-MS/MS Spectrum Linkage information can be obtained from the cross-ring cleavages around the linkage position. These fragments involve the rupture of two bonds in the pyranose ring. The ions thus... 

Figure 11.12. Identification of various linkages via cross-ring cleavages. (From ref. 5.)...

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