Collision‐induced dissociation of MCl+ adducts (M = Mg, Mn, Zn, Co, Ni and Cu) and Cu+ and Ag+ adducts of dithioalkyl ketene acetals

Self Cite

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.

Section: Resultssupporting

confidence: 80%

“…Ligated metal ions often induce unusual fragmentations 45–47. In order to examine the effect of ligated metal ions on the fragmentation of these acyclic sugar derivatives, the MS/MS spectra of [M+LMet] + ions (where LMet + = MgCl + , CaCl + , ZnCl + , CuCl + , MnCl + , NiCl + , CoCl + , InCl 2 + and BaCl + ) of 3 – 6 were recorded.…”

Section: Resultsmentioning

confidence: 99%

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

Madhusudanan

Kumar

Pathak

et al. 2003

Self Cite

“…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.…”

Section: [M+xcl]+supporting

confidence: 85%

“…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.…”

Section: [M+xcl]+mentioning

confidence: 65%

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

Madhusudanan

Kumar

Tiwari

et al. 2005

Self Cite

Electrospray ionization mass spectra of some glycosyl dithioacetals recorded in the presence of transition-metal chlorides, XCl2 (where X = Co, Mn and Zn), give abundant adduct ions such as [M+XCl]+ and [2M-H+X]+ and minor ions such as [M-H+X]+ and [2M+XCl]+. The tandem mass spectra of these adducts show characteristic elimination of neutral molecules such as H2O, HCl, EtSH, CH2O, C2H4O2/C2H4O. [M+XCl]+ ions fragment readily and the fragmentation appears to be stereochemically controlled as the relative abundances of the fragments are different for three stereoisomers. The added metal is lost as neutral molecules in the form of XCl(OH) and XCl(SEt). This is a predominant pathway in the ZnCl+ adducts. [2M+XCl]+ ions fragment preferentially by elimination of HCl, indicating strong metal interactions in the resulting dimeric [2M-H+X]+ ion. As there are several electron-rich centers in the molecule, the dimeric complex [2M-H+X]+ can have several structures and the observed fragmentations may reflect the sum of those of all these structures. The dimeric complexes fragment by elimination of neutral molecules leaving the dimeric interactions intact. The extent of fragmentation varies for the stereoisomers, leading to stereochemical differentiation.

“…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.…”

mentioning

confidence: 99%

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

Madeira

Rosa

Xavier

et al. 2010

Knowledge of the fragmentation mechanisms of lactones and their behaviour under electrospray ionization (ESI) conditions can be extended to larger and more complex natural products that contain an alpha,beta-unsaturated gamma-lactone moiety in their structure. Moreover, little is known about the gas-phase behaviour of alpha,beta-unsaturated gamma-lactones linked or fused to sugars. Therefore, five alpha,beta-unsaturated gamma-lactones (butenolides) fused to a pyranose ring, recently synthesized compounds with potential relevance regarding their biological properties, were investigated using ESI-MS and ESI-MS/MS in both positive and negative ion modes. Their fragmentation mechanisms and product ion structures were compared. It was observed that two isomers could be unambiguously distinguished in the negative ion mode by the fragmentation pathways of their deprotonated molecules as well as in the positive ion mode by the fragmentation pathways of either the protonated or the sodiated molecule. Fragmentation mechanisms are proposed taking into account the MS/MS data and semi-empirical calculations using the PM6 Hamiltonean. The semi-empirical calculations were also very useful in determining the most probable protonation and cationization sites.