A Partial Classical Resolution/Preparative Chiral Supercritical Fluid Chromatography Method for the Rapid Preparation of the Pivotal Intermediate in the Synthesis of Two Nonsteroidal Glucocorticoid Receptor Modulators

Preparative chiral supercritical fluid chromatography (SFC) employing an enantioenriched feedstock obtained via partial classical resolution enabled rapid access to kilogram quantities of a key intermediate common to two glucocorticoid (GC) receptor modulator candidates for which neither chemical nor enzymatic resolutions provided the desired chiral purity (>99.0 HPLC area percent). We developed a partial classical resolution of the racemate that afforded 85:15 enantioenriched mixtures with 90% recovery of the desired enantiomer and reduced the SFC processing time by 54%. The SFC method used a 5 cm × 28 cm column packed in-house with 20 μm Chiralpak AD, a total column flow rate of 150 g/min, a cosolvent composition of 12% methanol, and a column back pressure of 75 bar. The feed processing rate was up to 80 mL/h, which translated to 67 g/day of the enantioenriched mixture or 57 g/day of the desired enantiomer. This combined classical resolution/SFC process was employed to obtain a total of 1.0 kg of the de...