Electron spin resonance spectroscopic investigation of carbohydrate radicals. Part 2. Conformation and configuration in pyranos-1-yl radicals

Abstract

Carbohydrate free radicals wer regiospecifically generated at C-1 of acylated and alkylated pyranosyl derivatives in non-aqueous solution and their conformations were deduced from the hyperfine splittings of their e.s.r. spectra. The preferred conformations of the pyranosyl radicals are discussed in terms of a stabilizing interaction of the singly occupied p-orbital with the σ*-LUMO of the adjacent β-C–OR bond. From the α-¹³C coupling constant of the tetra-acetylglucosyl radical it is concluded that pyranosyl radicals are of π-type.