title: Elimination of 118 Da: a characteristic fragmentation in the tandem mass spectra of 11(15 --> 1)-abeo-taxanes.
abstract: The mechanism of the elimination of 118 Da from 11(15-->1)-abeo-taxanes was elucidated with the help of the tandem mass spectra of [M + NH(4)](+) and [M + Li](+) ions and the corresponding D-exchanged species. The fragmentation is triggered by the initial loss of the C-10 substituent. Evidence was also obtained for the stepwise elimination of acetone and acetic acid. Acetone is eliminated from the C-1 hydroxyisopropyl group and acetic acid from either the C-9 or C-7 acetoxy groups. The presence of an additional acetoxy group at C-13 leads to the direct elimination of 118 Da from [M + NH(4)](+) and [M + Li](+) ions involving the C-13 acetoxy group.
authors.affiliation: Regional Sophisticated Instrumentation Centre, Central Drug Research Institute, Lucknow-226 001, India. kpmadhusudanan@hotmail.com
authors.forename: K P
authors.initials: KP
authors.lastname: Madhusudanan
authors.forename: S K
authors.initials: SK
authors.lastname: Chattopadhyay
authors.forename: S
authors.initials: S
authors.lastname: Srivastava
mesh_terms: D007202:Indicators and Reagents; D008094:Lithium / Q000737:chemistry; D013058:Mass Spectrometry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D020946:Taxus / Q000737:chemistry*
chemical_list: D007202:Indicators and Reagents; D000644:Quaternary Ammonium Compounds; D008094:Lithium