title: Novel product ions of 2-aminoanilide and benzimidazole Ag(I) complexes using electrospray ionization with multi-stage tandem mass spectrometry.
abstract: BACKGROUND
  The 2-aminoaniline scaffold is of significant value to the pharmaceutical industry and is embedded in a number of pharmacophores including 2-aminoanilides and benzimidazoles. A novel application of coordination ion spray mass spectrometry (CIS-MS) for interrogating the silver ion (Ag(+)) complexes of a homologous series of these compounds using multi-stage tandem mass spectrometry is described. Unlike the ubiquitous alkali metal ion complexes, Ag(+) complexes of 2-aminoanilides and benzimidazoles were found to yield [M - H](+) ions in significant abundance via gas-phase elimination of the metal hydride (AgH) resulting in unique product ion cascades.
  
  
  METHODS
  Sample introduction was by liquid chromatography with mass spectrometry analysis performed on a hybrid linear ion trap/orbitrap instrument capable of high-resolution measurements.
  
  
  RESULTS
  Rigorous structural characterization by multi-stage tandem mass spectrometry using [M +  H](+), [M - H](-) and [M - H](+) precursor ions derived from ESI and CIS experiments was performed for the homologous series of 2-aminoanilide and benzimidazole compounds. A full tabular comparison of structural information resulting from these product ion cascades was produced.
  
  
  CONCLUSIONS
  Multi-stage tandem mass spectrometry of [M - H](+) ions resulting from Ag(+) complexes of 2-aminoanilides and benzimidazoles in CIS-MS experiments produced unique product ion cascades that exhibited complementary structural information to that obtained from tandem mass spectrometry of [M  +  H](+) and [M - H](-) ions by electrospray ionization (ESI). These observations may be broadly applicable to other compounds that are observed to form Ag(+) complexes and eliminate AgH.
authors.affiliation: GlaxoSmithKline, 5 Moore Drive, Research Triangle Park, NC 27709-3398, USA. byron.s.johnson@gsk.com
authors.forename: Byron S
authors.initials: BS
authors.lastname: Johnson
authors.forename: David J
authors.initials: DJ
authors.lastname: Burinsky
authors.forename: Svetlana A
authors.initials: SA
authors.lastname: Burova
authors.forename: Roman
authors.initials: R
authors.lastname: Davis
authors.forename: Russ N
authors.initials: RN
authors.lastname: Fitzgerald
authors.forename: Richard T
authors.initials: RT
authors.lastname: Matsuoka
mesh_terms: D000813:Anilides / Q000737:chemistry*; D001562:Benzimidazoles / Q000737:chemistry*; D056831:Coordination Complexes / Q000737:chemistry*; D007477:Ions / Q000737:chemistry; D012834:Silver / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000379:methods*
chemical_list: D000813:Anilides; D001562:Benzimidazoles; D056831:Coordination Complexes; D007477:Ions; D012834:Silver; C031000:benzimidazole