Solvent-free reactions at work towards densely functionalized targets: synthesis of 3-amino(azido)-3-deoxy-D-galactose, a key structural motif of galectin ligands

A straightforward approach is reported for the synthesis of 3-deoxy-3-amino(azido)-d-galactose, a key intermediate for the synthesis of high-affinity therapeutic inhibitors of galectins. The synthetic route highlights the viable applicability of experimentally simple solvent-free reactions in nearly half of the steps in the sequence, including a procedure specifically developed for a key epoxidation step. Unlike other known synthetic approaches, the current strategy stands out for the fast and efficient SN2 steps necessary for setting the nitrogen at C-3 with the correct configuration, achieved by taking advantage of intramolecular reactions.