Enantioselective synthesis of protected forms of (3R,5R)-5-hydroxypiperazic acid useful for synthesis

Protected versions of (3R,5R)-5-hydroxypiperazic acid were synthesized enantioselectively in two novel ways. The first derives its chirality from D-glutamic acid while the second uses an Evans amination and a diastereoselective bromolactonization to establish the two chiral centers. Given that this amino acid is a component of several depsipeptides, these two routes enable the synthesis of multigram quantities of protected versions of 2.