Metal-sugar complexes polyols

Yanagihara et al. [51 ] claimed that calcium was the only metal cation which catalyzed the epimerization they tried many others but only strontium had a weak effect. A closer investigation [52] showed cations that complex well with polyols [44] all catalyze the epimerization those metals tested by Yanagihara et al. were poor complex formers. Calcium hydroxide is best suited for this reaction because it has reasonable solubUity in water and is readily available. The reaction can also be conducted in methanol in which both calcium hydroxide and the sugars have only low solubility but when they are both present, the solvent dissolves many of them, owing to complex formation. 

---