Structural confirmation of ostreocin‐D by application of negative‐ion fast‐atom bombardment collision‐induced dissociation tandem mass spectrometric methods

Negative‐ion fast‐atom bombardment collision‐induced dissociation tandem mass spectrometric (FAB‐CID‐MS/MS) methodology was successfully applied to verify the highly complex structure of ostreocin‐D (MW 2633), a new palytoxin analog isolated from the marine dinoflagellate Ostreopsis siamensis and proposed to be 42‐hydroxy‐3,26‐didemethyl‐19,44‐dideoxypalytoxin based on NMR data. The charge‐remote fragmentations were facilitated by a negative charge introduced to a terminal amino group or to a hydroxyl group at the other terminus by a reaction with 2‐sulfobenzoic acid cyclic anhydride. Product ions generated from the [M − H] − ions provided information on the structural details of ostreocin‐D. Comparisons between the spectral data for ostreocin‐D and palytoxin also provided a rational basis for the assignments of product ions. Copyright © 2002 John Wiley & Sons, Ltd.