Studies on anhydro-osazones. Part 5. Structure and anomeric configuration of the C-nucleoside analogues obtained from the dehydration of D-gluco- and D-manno-hept-2-ulose phenylosazones
Abstract
Dehydration of D-gluco- and D-manno-hept-2-ulose phenylosazones with methanolic sulphuric acid afforded the anomeric furanosyl anydro-osazone pair: 3,6-anhydro-D-manno-hept-2-ulose phenylosazone (2), and the gluco-analogue osazone (3). A new type of anomeric pyranosyl anhdro-osazone [3,7-anhydro-D-manno-hept-2-ulose phenylosazone (4) and the gluco-analogue (5)] was also identified. Refluxing the anhydro-osazones with copper sulphate afforded the anomeric furanosyl C-nucleoside analogues 4-α-D-arabinofuranosyl-2-phenyl-v-triazole (6) and the β-isomer (7), and the arabinopyranosyl isomers (8) and (9). The structures and anomeric configurations of the products were determined by periodiate oxidation, o.r.d., and n.m.r. spectroscopy. The mechanism of the dehydration and the mass spectra of compounds (6)–(9) are discussed.