How is (S)-4-[4-(Dimethylamino)-1-(4-fluorophenyl)-1-hydroxybutyl]-3-(hydroxymethyl)-benzonitrile Di-p-toluoyl-D-tartrate Salt (2:1) (CAS: 128173-53-5) typically synthesized?

This compound is typically synthesized via a multistep process involving alkylation, amination, and esterification. The key steps include the reaction of 4-fluorophenylacetic acid with dimethylamine, followed by coupling with a hydroxybutyric acid derivative. The final step involves complexation with di-p-toluoyl-D-tartrate to form the salt. This process requires careful control of pH and temperature to achieve high yield and selectivity.