Chiral chemistry

Classical Resolutions

a. Dynamic Resolution What would be a perfect resolution? It would be when one of the two isomers is removed, the wrong one is racemised in situ, resulting in larger proportions of the correct isomer. Such separations, named dynamic resolutions, are often the most cost-effective way of creating a pure chiral molecule from a racemicmixture.

b. Salt Resolution Achiral synthesis is often considered as faster and cost efficient compared to chiral synthesis. However the resolution step can be time-consuming and difficult. The most classical option for the resolution remains selective crystallization. Diastereoisomers resolutions involving chiral acids or bases are very frequent. Groupe Novasep has optimized such methods in combination with chromatography.

Stereo-enantio-specific Reactions
 
Complex APIs are often stereochemically demanding: the use of modern synthetic methods such as Transition Metal Catalysis (TMC) are key for cost effective and timely API manufacture with the advantage of direct synthesis of the desired enantiomer and the commercial availability of a broad range of catalyst systems.

Enzymatic Resolutions
 
Combining enzymatic resolutions and reverse substitutions can offer economic solutions. In the case described, Novasep Synthesis has developed a new synthetic route involving an enantioselective acetylation followed by a Mitsunobu reaction of the non reacted alcohol. Such approach has replaced a low-yield crystallization and resulted in signifi cant savings.