Product ion studies of diastereomeric benzo[ghi]fluoranthene tetraols by matrix-assisted laser desorption/ionization time-of-flight mass spectrometryand post-source decay

The product ion formation characteristics of the four diastereomeric tetrah ydroxy benzo[ghi] fluoranthene compounds formed by hydrolysis of the syn an d anti diastereomers of trans-3,4-dihydroxy-5,5a-epoxy-3,4,5,5a-tetrahydroz o[ghi]fluoranthene are studied using matrix-assisted laser desorption/ioniz ation and post-source decay (PSD) to determine a correlation between the fr agmentation characteristics of these tetraols and the structures of the dio lepoxide diastereomers from which they are hydrolyzed. The tetraols formed by the trans ring opening of the diol epoxides during hydrolysis yield prod uct ion spectra specific for the syn and anti configurations of their precu rsor diol epoxides. All four diastereomeric tetraols form product ions by t he losses of one and/or two water molecules in varying proportions when lit hium-cationized molecule ions (m/z 301) are selected for PSD product ion an alysis. The differences in the PSD spectra of these four Li+-cationized mol ecules are rationalized in terms of a water loss mechanism that involves th e 1,2 elimination of a hydrogen atom and hydroxyl group that are cis with r espect to each other on adjacent carbons. (C) 2001 American Society for Mas s Spectrometry.