The photochemistry of ketones derived from carbohydrates. Part 9. Formation of O- and C-ribofuranoside derivatives by photodecarbonylation of O- and C-glycosides of lyxo-hexopyranos-4-ulose derivatives

Abstract

The syntheses of 6-deoxy-2,3-O-isopropylidene-α-L-lyxo-hexopyranosyl-4-ulose-ethane (7) and -benzene (8), and the assignment of their anomeric configurations by ¹H and ¹³C n.m.r. spectroscopy, are described. The preparations of a number of O-glycosid-4-ulose derivatives [(4)–(6) and (19)] related stereochemically to these C-glycosides are also reported. Irradiation of all these 4-ulose derivatives in solution with u.v. light causes them to decarbonylate and form as the sole non-polar photoproducts the respective O- and C-furanosides with preponderantly the β-D-ribo-structure.