RESUMEN
Octahedral nickel(II)-N-glycoside complexes of glucose, galactose, mannose, and talose were synthesized and analyzed by electrospray ionization (ESI). A resulting tricoordinate species generated from the octahedral complex was subjected to collision-induced dissociation. A highly stereoselective dissociation pathway involving beta-hydrogen elimination and cross-ring cleavages was observed in complexes possessing equatorial C-2 substituents. (2)H- and (13)C-labeling experiments indicate that the hydrogen on C-2 and a labile proton are involved in the beta-hydrogen elimination. Additionally, C-4, C-5, and C-6 are shown to be lost from the monosaccharide as a result of the cross-ring cleavages. A mechanism is postulated to explain the stereoselectivity of this dissociation.
RESUMEN
The formation of cyclic sulfates (4) from syn,syn-3-[N-(benzyloxycarbonyl)amino] 1,2-diols provides a common intermediate to access other diastereomers via two inversion procedures. Thermolysis of the cyclic sulfates in acetonitrile normally leads to inversion of the distal hydroxyl group to form a 1,3-oxazin-2-one (6). Catalytic hydrogenation of the cyclic sulfates under basic conditions (NEt(3)) results in inversion at the proximal hydroxyl group to form a 1,3-oxazolidin-2-one (5).
