Methods are provided for the conversion of isosorbide to isoidide, wherein the isosorbide contains sorbitan impurities. The impurities in the isosorbide subjected to epimerization are converted to hydrodeoxygenation products. A method for synthesizing isoidide, comprising, providing an isosorbide containing one or more sorbitans; and, epimerizing the isosorbide to form an epimerization product comprising isoidide and hydrodeoxygenation products.