α-DEOXY-α-HYDROXYAMINO SUGAR PHOSPHONATES AND THE CORRESPONDING NITROXIDE FREE-RADICALS

Article abstract of DOI:10.1016/0008-6215(85)85211-3

Treatment of sugar aldonitrones with dialkyl phosphites gave sugar α-deoxy-α-N-(hydroxy-N-methylamino)phosphonates, often highly stereoselectively.Repeated nucleophilic addition to a nitrone followed by oxidation of the resulting hydroxylamine allows the "first generation" nitrone, 1,2-O-isopropylidene-α-D-xylo-pentodialdo-1,4-furanose 5-(N-methyloxime), to be converted into the "third generation" cyclic nitrone, <(4R)-4-diethoxyphosphoryl-5H,6H-1,3-oxazino><6,5-c>(1,2-O-isopropylidene-α-D-xylo-tetrofuranose) N-oxide.The configurational and conformational assignments for all the new compounds prepared were based on short and long-range H,H, H,P, and P,C coupligs, and new empirical rules regarding long-range H,P couplings are proposed.The sugar α-deoxy-α-hydroxyaminophosphonates spontaneously oxidised in the air to give the corresponding nitroxide free-radicals, which afforded good e.s.r. spectra that allowed epimers at the α-carbon atom to be discriminated.