Formation of methyl 2,6-anhydro-3,4-O-isopropylidene-α-and -β-D-talopyranosides by an intramolecular displacement in the methanolysis of 1,6-anhydro-3,4-O-isopropylidene-2-O-methylsulphonyl-β-D-galactopyranose

Abstract

Methyl 2,6-anhydro-3,4-O-isopropylidene-α- and -β-D-talopyranosides are formed when 1,6-anhydro-3,4-O-isopropylidene-2-O-methylsulphonyl-β-D-galactopyranose is heated in methanol containing potassium fluoride dihydrate. The reaction apparently proceeds via an intramolecular displacement, for the isomeric 1,6-anhydro-3,4-O-isopropylidene-2-O-methylsulphonyl-β-D-talopyranose is unreactive in displacement reactions. The utility of potassium fluoride in methanol as a non-nucleophilic base is discussed.