| Abstract: | Cyclic butane- and methaneboronic esters of dimethylphosphates of glucose, galactose, mannose, fructose and methyl gluconate have been examined by mass spectrometry. High resolution information and deuterium labeling of all six carbons of glucose, as well as of the methylphosphate groups, permits elucidation of the origin of various ions, which can be grouped according to their probable mechanism of formation. In each case, the intensity of the [M – R]+ ion can be rationalized, in stereochemical terms, by the ease with which incipient positive charge on boron can be stabilized by the phosphate group. This interaction also gives rise to rearrangement ions containing a B? O? P linkage. Other effects of structure on fragmentation pattern are discussed. Retention of specific portions of the glucose skeleton in ions with clearly defined label shift behavior, as well as the preservation of intact sugar moieties in intense [M – R]+ ions, suggests applications for stable isotope analyses. These are discussed in terms of their advantages over silicon-containing derivatives. |
