Radical reactions of carbohydrates. Part 4. Electron spin resonance studies of radical-induced oxidation of some aldopentoses, sucrose, and compounds containing furanose rings

Abstract

E.s.r. spectra detected when ·OH reacts with the aldopentoses xylose and ribose are attributed to pyranose ring radicals, formed in essentially unselective attack; in contrast, in the corresponding reactions of the model compound tetrahydrofurfuryl alcohol, as well as some isopropylidene derivatives of glucofuranose, the hydrogen atoms on the carbon atoms adjacent to oxygen in a furanose ring are activated towards abstraction. A similar activation, evidently stereoelectronic in origin, is also proposed to account for the enhanced reactivity of C(5′)–H in the furanose ring of sucrose, a finding which may have particular relevance to the mechanism of radiation damage in DNA.