Nickel(II)-catalyzed rearrangements of free sugars

C-2 Epimerization of aldoses and ketoses catalyzed by the Ni(ll) complex is described. Both epimerization and the preparation of side-chained sugars p roceed in the ternary nickel complex through stereospecific rearrangement o f the carbon skeleton, that is, from (1-C-13)-D-glucose into (2-C-13)-D-man nose and from (2-C-13)-D-fructose into (2-C-13)-D-hamamelose, and vice vers a. The structure of the ligand in the complex plays an important role durin g the epimerization. The epimerization proceeds more smoothly in both metha nolic and aqueous solutions with a more hydrophobic ligand such as N,N ' -h igher alkylated ethylenediamine. Due to their ability to self-aggregate in water, the organized metallomicelles can provide an appropriate reaction sy stem for the epimerization of aldoses. The chirality of the ligand contribu tes to the shift of the equilibrium between the two C-2 epimers.