A general procedure for degrading radioactive aldoses

Abstract

A procedure is described for determining the radioactivity of individual carbon atoms in aldopentoses and aldohexoses labeled with 14C. Each position is obtained independently from 0.7 millimole of starting methyl glycoside. The methyl glycoside is oxidized with periodic acid, yielding C-3 as formic acid and a dialdehyde oxidized with Br 2 to strontium methoxydiglycolate. Formic acid was obtained for counting by sublimation of its ammonium salt. The crude strontium salt was hydrolyzed to glyoxylic and glyceric (or glycolic) acid, and the latter mixture separated quantitatively on a Dowex 1 acetate column. The glyoxylic acid was isolated as its sodium salt (C-1 + C-2), which was decarboxylated with sodium periodate to give carbon dioxide (C-2) and formic acid (C-1). Glyceric acid was isolated as its calcium salt (C-4 + C-5 + C-6), which was oxidized with sodium periodate to give C-4 as CO 2, C-5 as formic acid, and C-6 as formaldehyde. Glycolic acid, obtained from pentoses, was isolated as its calcium salt (C-4 + C-5) and was degraded with lead tetraacetate to yield C-4 as CO 2 and C-5 as formaldehyde. The method was tested with four different methyl glycosides possessing a 20-fold range in specific activity with satisfactory results. The procedure produces four white, crystalline derivatives and two carbon dioxides trapped in ethanolamine/ethylene glycol monomethyl ether for direct liquid scintillation counting.