Analysis and Comparison of Commonly Used Acidic Resolving Agents in Diastereomeric Salt Resolution – Examples for DL-Serine

Diastereomeric salt resolution is still the most relevant technique in chiral resolution processes, e.g. for pharmaceutical relevant substances. For this purpose the choice of a suitable corresponding resolving agent is very important in respect of optimal yield, chemical purity and diastereomeric excess. Thus the solid phase behavior of diastereomeric salts is a crucial parameter and should be investigated prior to any resolution experiment. Within this contribution 3 commonly used acid resolving agents, 2,3-dibenzoyl-l-tartaric acid, l-(+)-mandelic acid, and l-(+)-tartaric acid, are compared for the resolution of the model compound dl-serine. The behavior of each diastereomeric salt pair was analyzed experimentally and is discussed with the help of phase diagrams.