Catalytic Asymmetric Amination of meso-Epoxide Using Soy Polysaccharide (Soyafibe S-DN)

Abstract

Abstract The asymmetric amination of epoxides is an effective method to synthesize chiral β-aminoalcohols and their components as pharmaceuticals. We have developed a new catalyst system for the asymmetric amination of 1,2-epoxycyclohexane with cyclopropylamine. We have also found that water-soluble soy polysaccharide (Soyafibe S-DN) functions as a catalyst. This catalytic reaction proceeded under mild conditions in hydrous toluene at 37–40 °C. (1R,2R)-2-(cyclopropylamino)cyclohexan-1-ol was obtained at 64% enantiomeric excess (ee) by the asymmetric amination of 1,2-epoxycyclohexane with cyclopropylamine using this catalyst system; it was also made at >99% ee by purification as the fumarate salt. The catalytic activity of this soluble soy polysaccharide remained unchanged, even when treated with a protease, but its activity disappeared when treated with a sugar chain degrading enzyme. These results indicate that the polysaccharide rather than the protein acts as the catalyst for this reaction. Thus, we have discovered for the first time that polysaccharides can act as asymmetric catalysts for the amination of 1,2-epoxycyclohexane.