Functionalization at C-2 of L-idose and L-iduronic acid derivatives

Several synthetic strategies for obtaining C-2 functionalized l-idose or l-iduronic acid derivatives were investigated. Synthesis of protected derivatives with a C-2 hydroxy group proceeded smoothly, however, these compounds were prone to competing elimination reactions during subsequent oxidation and HWE steps. Elimination during oxidation could be minimized by replacing benzylidenes with alternative protecting groups, resulting in satisfactory overall yields of the corresponding unsaturated carboxylate derivatives following HWE reaction. However, the corresponding phosphonate analogues were not accessible via this method. A 1,6-anhydro-l-idose derivative was successfully converted into a C-2 phosphonate derivative in good yield via an oxidation/HWE sequence without competing elimination, however, it could not be successfully elaborated into the desired final product.