Fragmentation pattern of regioselectively O-methylated maltooligosaccharides in electrospray ionisation-mass spectrometry/collision induced dissociation

Maltose, maltotriose and maltotetraose derivatives consisting of regioselectively O-methylated glucosyl units have been obtained via synthesis and partial hydrolysis of the corresponding beta-cyclodextrin derivatives. The fragmentation mode of the sodium adducts in electrospray ionisation-mass spectrometry (ESI-MS)/collision induced dissociation (CID; ESI-MS2) was investigated and interpreted with regard to the positions of the methyl groups. Nearly no influence of the status of position 6 in the glucosyl units was recognised. While O-2-methylation strongly favoured cross ring fragmentation, cleavage of glucosidic linkages is preferred for the O-3-methylated maltooligomers yielding dimeric (from trioses) or also trimeric (from tetraoses) Y and B ions of similar intensities. When both secondary OH groups were blocked, formation of Yn-1 became the preferred process. (C) 2003 Elsevier B.V. All rights reserved.