Synthetic intermediates and improved processes for preparing rock inhibitors

Provided herein are methods of synthesizing netarsudil, and intermediates thereof, in high yield and at large commercial scale. A key intermediate in this synthesis is the preparation of piperidinium (S)-3-((tert-butoxycarbonyl)amino)-2-(4-(((2,4-dimethylbenzoyl)oxy)methyl)phenyl)propanoate, a salt that has been found to be easily purified by recrystallization.