Flavan derivatives. XXV. Mass spectra of 3-hydroxyflavanones, flavan-3-ols, and flavan-3,4-diols

Abstract

Mass spectral data are reported for eight 3-hydroxyflavanones, ten flavan-3-ols, and twelve flavan-3,4-diol derivatives. The principal fragmentation of each of these three classes of compound yields ions derived by retro Diels-Alder fission of the heterocyclic nucleus, accompanied in the case of 3-hydroxyflavanones and flavan-3-ols by hydrogen transfer from the 3-hydroxyl group to the A ring fragment. Deuteration experiments with flavan-3-ols confirmed the origin of the hydrogen atom transferred. Flavan-3,4-diols show two characteristic fragmentation patterns depending on the insertion technique. Mass spectra obtained by indirect insertion of flavan-3,4-diols showed a very marked enhancement of the intensities of the M-18 and M-18-28 peaks, and of their fragmentation ions, compared with spectra obtained by direct insertion.