Simple and Efficient Method for the Synthesis of Galactofuranosides

Abstract

An efficient and improved one-pot method for the synthesis of galactofuranosides via iodine-promoted cyclization of galactose diethyl dithioacetal in the presence of alcohol, acting both as solvent and nucleophile, is described. The reaction is carried out at room temperature. Alcohols, such as methanol, cyclohexanol and tert-butanol, were used as nucleophiles for the reaction using 2%, 3% and 5% iodine promoter, respectively. A key finding in this study was that the iodine-promoted cyclization of galactose diethyl dithioacetal with alcohol led to selective formation of β-galactofuranoside allowing the efficient preparation of derivatives of this monosaccharide.

Protecting-group-free synthesis of clevudine (l-FMAU), a treatment of the hepatitis B virus

“…Disappointed with the low yield for the pyranose-to-furanose isomerisation of 2-deoxy-2-fluorogalactose 11 , we were compelled to explore other methods to generate the 2-deoxy-2-fluoro- d -galactofuranose scaffold. The group of Completo reported a simple and efficient strategy for the synthesis of galactofuranosides via iodine-promoted cyclization of galactose diethyl dithioacetal, 31 based on the work of Lowary. 32 This strategy was unprecedented with fluorinated galactose, but seems suitable to generate 2-deoxy-2-fluoro-galactofuranosides.…”