STEREOSELECTIVE BETA-HYDROGEN ELIMINATION FROM NICKEL(II)-N-GLYCOSIDECOMPLEXES

Octahedral nickel(II)-N-glycoside complexes of glucose, galactose, man nose, and talose were synthesized and analyzed by electrospray ionizat ion (ESI). A resulting tricoordinate species generated from the octahe dral complex was subjected to collision-induced dissociation. A highly stereoselective dissociation pathway involving beta-hydrogen eliminat ion and cross-ring cleavages was observed in complexes possessing equa torial C-2 substituents. H-2- and C-13-labeling experiments indicate t hat the hydrogen on C-2 and a labile proton are involved in the beta-h ydrogen elimination. Additionally, C-4, C-5, and C-6 are shown to be l ast from the monosaccharide as a result of the cross-ring cleavages. a mechanism is postulated to explain the stereoselectivity of this diss ociation.