Fig. 1: The synthesis of the key intermediate of cariprazine.

a Retrosynthetic scheme for cariprazine. b Patented chemical route to the key intermediate (box of black dotted line). Transaminase-catalyzed alternative synthetic routes for cariprazine key intermediate trans-1a can exploit c proper diastereotope selectivity of transaminase-catalyzed amination of the corresponding ketone 2a (box of red dotted line) or d the proper diastereomer selectivity of a transaminase preferring deamination of the cis-diastereomer cis-2a from the cis/trans-diastereomeric mixture forming in the chemical route (box of blue dotted line).