Efficient synthesis of (S,S)-ethambutol from l-methionine

Starting from readily available amino acid l-methionine, an efficient synthesis of the tuberculostatic agent (S,S)-ethambutol has been developed. The key steps in the synthetic sequence involve: dimerization of methionine methyl ester through oxalyl diamide formation, Raney nickel desulfurization of the terminal thiomethyl groups, and a one-pot exhaustive reduction of the oxalamide and the diester functionalities to afford the desired enantiopure (S,S)-ethambutol in good overall yield.