Tandem mass spectra of ammonium ion, metal ion and ligated metal ion adducts of acyclic sugar derivatives

Abstract

The tandem mass (MS/MS) spectra of ammonium ion, metal ion and ligated metal ion adducts of chain-extended acyclic nitro-containing deoxyglucose and deoxygalactose derivatives have been studied. The ammonium adducts fragment primarily by elimination of ammonia followed by acetic acid, thus not giving much structural information. In contrast, cationization of these compounds by metal ions and ligated metal ions gave structurally informative and useful fragment ions on MS/MS. The metal ions and ligated metal ions play an important role in controlling and directing fragmentation. Retro-aldol fragmentation is facilitated by metal ions such as Li(+), Na(+), Ag(+) and Cu(+), whereas the adducts with higher alkali metal ions such as Rb(+) and Cs(+) fragment to give only the corresponding metal ions. The divalent metal ions such as Cu(2+) and Ba(2+) also induce retro-aldol fragmentation. However, the charge is carried by the aldehyde fragment in the case of Cu(2+) adducts, whereas the nitroalkane fragment carries the charge in the case of Ba(2+) adducts. Ligated metal ions such as ZnCl(+), CuCl(+), InCl(2) (+) and BaCl(+) also behave similarly and induce retro-aldol fragmentation in these acyclic sugars. Both the metal ion and ligated metal ion adducts can fragment by elimination of metal-containing neutral molecules.

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

“…The MS 2 mass spectra of the ion at m/z 163 from 1 and of the ion at the same m/z generated from glucose were identical, containing the same product ions at m/z 145, 127 and 85, corresponding to eliminations of H 2 O, 2H 2 O and (H 2 O+C 2 H 4 O 2 ), respectively; these observations are consistent with cyclization and formation of the gluconium ion at m/z 163. Similar metal eliminations were reported by us previously in MS 2 spectra of ligated metal‐cationized ketene dithioacetals,26 acyclic sugar derivatives,27 and monosaccharides (K. P. Madhusudanan, S. Kanojiya, B. Kumar, manuscript in preparation). These metal eliminations become more prominent as the metal is changed from Co and Mn to Zn, and becomes the predominant fragmentation pathway in the MS 2 spectra of the ZnCl + adducts.…”

“…DCl is lost in place of HCl for the D‐exchanged precursor ( 1A ), indicating the loss of a replaceable hydrogen. Elimination of HCl is a favored dissociation pathway and has been reported previously by several workers 26–30. HCl elimination can potentially occur from multiple sites leading to [MH+Co] + ions.…”

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

“…For instance, protonated species decompose much more readily than metal cationized species 15–17. Metal cationization alters the stability of the resulting products, changing the dissociation pathways 18–20 …”

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.…”