Formation of a Salt Enables Complete Deracemization of a Racemic Compound through Viedma Ripening

Abstract

Chiral purification is a very important step in the production of many products such as active pharmaceutical ingredients (API). These procedures are typically limited to a maximum yield of 50%. Methods that include a racemization method, such as Viedma ripening, offer a theoretical yield of 100%. Racemic conglomerate formation is a necessary condition for chiral purification processes that exploit crystallization, such as Viedma ripening. This condition forms a limiting factor because only 10% of the chiral organic molecules crystallize in this way; the other 90% form racemic compounds. For two compounds that crystallize as racemic compounds we demonstrate that salt formation can transform these into racemic conglomerates and show that these can subsequently be fully deracemized using Viedma ripening. Salt formation thus promises to be a crystal engineering tool to significantly extend the applicability of Viedma ripening.