Low-energy collision-induced dissociation of B-1-type sugar ions formed from peracetylated methyl pentosides and methyl 6-deoxyhexosides

Low-energy collision-induced dissociation (CID) Has explored for the purpos e of differentiating between isomeric pertrideuteroacetylated aldopentoside s, 6-deoxyaldohexosides and their respective furanosidic and pyranosidic an alogues. The 1-O-methylated derivatives were analyzed by gas chromatography /chemical ionization (CPI,) tandem mass spectrometry. B-1 ions (formally C( 1) carbenium ions), which are expected to reflect the core structure of the parent sugar and which were produced by the elimination of methanol from t he protonated glycoside derivatives, were used as precursor ions to obtain the corresponding CID spectra. In general, strong similarities which impede an unepuivocal differentiation of the individual constituents were found i n the spectral patterns of the different isomeric pairs However, examinatio n of the pseudo-breakdown behavior of the B-1 ions over the range 5-35 eV r evealed improved distinction windows which provide for a fuller differentia ting capability between five-and six-membered ring isomers including even t he most problematic ribose derivatives, The reliability of the analyses is enhanced by the high reproducibility (s < 10%) of these ratios. The conside rable similarity between the tandem mass spectra of certain furanosidic and pyranosidic B-1 ions is highly suggestive of a partial loss of structural integrity, mainly due to ring contraction, which occurs to different extent s in the different isomers, Copyright (C) 1999 John Wiley & Sons, Ltd.