[11] Chemical synthesis of monosaccharides enriched with carbon isotopes

Publisher Summary This chapter describes the chemical synthesis of monosaccharides enriched with carbon isotopes. This method utilizes the the facile condensation of cyanide anion with an aldehyde at controlled pH to form a pair of 2-epimeric aldononitriles. The aldononitriles are stabilized at pH 4 to produce a pair of 2-epimeric alditylimines that hydrolyze spontaneously to the corresponding aldoses. The epimers are separated by chromatography on Dowex 50 in the Ba 2+ or Ca 2+ form. The simple aldoses, deoxyaldoses, and other water-soluble aldose derivatives are used as acceptors. Aldoses enriched at C-1 are prepared when cyanide enriched with 13 C or 14 C is used. The formation of aldononitriles from stoichiometric amounts of reactants is essentially quantitative at pH 8.0 when the starting aldose has four or fewer carbons. Glycolaldehyde and the pentoses are obtained from commercial sources in high purity. The concentrations of reactants used for aldononitrile formation are tabulated in the chapter. The conditions for hydrogenation-solvolysis depend on the chain length of the aldononitrile. The molybdate-catalyzed interconversion of aldoses is accomplished by mannose and glucose.