COMPLEXES OF COBALT(III) WITH D-FRUCTOSE AND PHENANTHROLINE

D-Fructose and 1,10-phenanthroline form complexes with Co(III). Configurations about Co(III) are assigned from the CD and ORD spectra of the separated Lambda and Delta diastereomers, and Lambda strongly predominates in the mixture, Most of the H-1 NMR signals of the complexes are shifted strongly upfield, relative to those of D-fructose, due to shielding by aromatic residues, and the effect is especially strong for hydrogens at positions 1 and 6. Signals of the fructose residue are assigned for the Lambda diastereomer and coupling constants estimated, but only some of the signals can be assigned for the Delta diastereomer. The marked changes in chemical shifts on formation of the complexes from fructose are rationalized in terms of predicted conformations based on molecular-mechanics calculations with MM2 parameters, which predict the higher stability of the Lambda over the Delta diastereomer, and also complexation at positions 2 and 3.