Effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals

Abstract

The effect of metal cationization on the tandem mass spectra of glycosyl dithioacetals of glucose, mannose, galactose, rhamnose, arabinose and xylose was studied by electrospray ionization mass spectrometry under ammonium and metal (Li, Na, Ag and Cu) ion cationization conditions. The ammonium-cationized glycosyl dithioacetals fragment by loss of ammonia followed by either two molecules of EtSH or one molecule of EtSH and one molecule of H2O. Lithium cationization leads to additional eliminations such as EtSEt and EtSSEt and C-C cleavages. Elimination of EtSH is not observed under sodium cationization. Silver cationization, on the other hand, leads to additional fragmentations involving the elimination of silver as AgOH and AgSEt. Copper cationization results in adducts where copper has undergone a change of oxidation state from II to I. Li+, Ag+ and Cu+ cationization seem to favour cyclization resulting in elimination of EtSH. However, the mechanisms seem to be differently affected by different metal ions. Li+ and Ag+ cationization appear to be non-specific and favour cyclization involving C2-, C4- and C5-hydroxyl hydrogens, whereas Cu+ cationization seems to favour cyclization involving C4-hydroxyl hydrogen.

Tandem mass spectra of transition‐metal ion adducts of glycosyl dithioacetals; distinction among stereoisomers

“…The m/z value of the ions corresponding to C 2 H 4 O 2 elimination is partly shifted to m/z 223 in 1B , suggesting that multiple mechanisms operate for this elimination. This is consistent with involvement of cyclization in EtSH elimination, as proposed by us previously 24…”

“…Metal cationization alters the stability of the resulting products and thus changes the dissociation pathways 23. As a continuation of our earlier study on the effect of metal ions such as Li + , Na + , Ag + and Cu + on the MS/MS spectra of glycosyl dithioacetals,24 we have examined the MS/MS spectra of glycosyl dithioacetals 1 – 6 complexed to ligated metal ions (CoCl + , MnCl + and ZnCl + ) with a view to studying the effect of different metal ions on fragmentation, and to explore the possibility of distinguishing the stereoisomers. …”

Electrospray ionization mass spectrometric analysis of newly synthesized α,β‐unsaturated γ‐lactones fused to sugars

“…8,13 Knowledge of the fragmentation mechanisms of lactones and the behaviour of these compounds under ESI conditions can be extended to larger and more complex natural products that contain the a,b-unsaturated g-lactone moiety in their structure. Little is known about the gas-phase behaviour of a,b-unsaturated g-lactones linked or fused to sugars, [14][15][16][17] and to the best of our knowledge, there have been few studies of the fragmentation behaviour of monosaccharides. 18 We decided, therefore, to perform a detailed study using ESI-MS and ESI-MS/MS on five a,b-unsaturated g-lactones (butenolides) fused to a furanose ring, recently synthesized compounds which may possess interesting biological properties.…”

Mass Spectrometry in India

“…114 Metal cationization involving alkali and transition metal ions and silver ion under ESI has been studied with acyclic sugar derivatives, cyclodextrins, glycosyl dithioacetals, aldohexoses, ketohexoses, glycosyl sulfides, sulfoxides and sulfones and the fragmentations under CID have been rationalised. [115][116][117][118][119] CID of ammonium adducts of monosaccharides has differentiated diastereoisomers. In addition, it was found that the ion abundances from CID of oxocarbenium ions generated from aldohexoses and ketohexoses under ESI conditions were different for diastereoisomers and the ratios of the abundances of two of the major ions m/z 85 and m/z 91 were different in the aldohexoses and the ketohexoses.…”