| The earliest literature mention of pyrone glycosides was in a study by Jerzmanowska and Markiewicz on the glycosidation of aglycons containing an internal hydrogen bond. This study also suggested the possibility of pyrone glycosides as model compounds for more complex 3-hydroxypyrone systems. Thereafter, the utility of one pyrone glycoside as a synthetic precursor of pyridone glycosides was investigated. Since these studies, some pyrone glucosides have been found by several research groups to occur naturally and have some taxonomic significance; one has been shown to have pharmacological properties. A successful synthesis of a pyrone riboside has appeared in the literature.;A variety of synthetic conditions have been examined for the glycosidation of pyromeconic acid with glucopyranose derivatives. With pentaacetyl (alpha)- and (beta)-D-glucose, SnCl(,4) in refluxing CH(,2)Cl(,2) or benzene, and ZnCl(,2) or p-toluenesulfonic acid in a melt under vacuum distillation conditions were found to be ineffective in forming the pyrone tetraacetyl glucoside. Glucosidation was also not achieved with acetobromoglucose in the presence of Ag(,2)CO(,3)/I(,2)/neutral solvent, Ag(,2)O/pyridine, Li(,2)CO(,3)/ neutral solvent, Hg(CN)(,2) or Hg(CN)(,2)/HgBr(,2) in acetonitrile, aqueous KOH, or K(,2)CO(,3) in refluxing acetone. Reasons for the failure of these reactions are discussed.;Glycosidation of pyromeconic acid was successfully carried out by a procedure based on an anhydrous modification of Michael's glycosidation. This procedure was found to be applicable to all combinations of pyrones and glycosyl derivatives in this study. . . . (Author's abstract exceeds stipulated maximum length. Discontinued here with permission of author.) UMI.;With these interests plus the value of several hydroxypyrone aglycons as flavor additives and the possible use of pyrone glycosides as substrates in glycosidase assays in mind, the synthesis and structural investigation of a series of 2-substituted 3-hydroxy and 5-hydroxy pyrone glycosides has been carried out. These glycosides have the general structure I. This study has resulted in the synthesis of glucosides (R=1-O-(beta)-D-glucopyranosyl), galactosides (R=1-O-(beta)-D-galactopyranosyl) and D-arabinosides (R=1-O-(alpha)-D-arabinopyranosyl) of pyromeconic acid (R'=R''=H), maltol (R'=CH(,3); R''=H), -hydroxymaltol (R'=CH(,2)OH; R''=H), veltol (R'=CH(,2)CH(,3); R''=H) and kojic acid (R'=H; R''=CH(,2)OH). |
