Methyl α- and β-D-threofuranosides (I and II) and methyl α- and β-D-erythrofuranosides (VII and VIII) were prepared in a modified manner. For the preparation of monomethyl ethers of compounds I and II 1,2-O-isopropylidene-β-D-threofuranose (IV) was prepared as the starting compound. For the synthesis of monomethyl ethers of compounds VII and VIII partial methylation of these diols was made use of.