US Patent 9346738 Process for the preparation of treprostinil and derivatives thereof

A method for the preparation of treprostinil and its derivatives is described. In contrast to prior art, this method utilizes an easily scalable enzymatic resolution of a key intermediate for making these compounds. Another significant improvement of the described method over prior methods is the regioselective Claisen rearrangement of a 5-allyloxy-benzaldehyde precursor, which is facilitated by a bromo substituent in 2-position.