Macrocyclic glycopeptide chiral selectors bonded to core-shell particles enables enantiopurity analysis of the entire verubecestat synthetic route

Verubecestat is an inhibitor of β-site amyloid precursor protein cleaving enzyme 1 (BACE1) being evaluated in clinical trials for the treatment of Alzheimer's disease. Synthetic route development involves diastereoselective transformations with a need for enantiomeric excess (ee) determination of each intermediate and final active pharmaceutical ingredient (API). The analytical technical package of validated methods relies on enantioselective SFC and RPLC separations using multiple 3 and 5 μm coated polysaccharide-based chiral stationary phases (CSPs) and mobile phases combinations. Evaluation of recently developed chiral columns revealed a single chiral selector (Teicoplanin) bonded to 2.7 μm core-shell particles using H₃PO₄ in H₂O/ACN and triethylammonium acetate: methanol based eluents at different isocratic compositions allowed good enatioseparation of all verubecestat intermediates. EE determination of verubecestat is easily performed on NicoShell, another macrocyclic glycopeptide chiral selector bonded to 2.7 μm superficially porous particles. This approach enables fast and reliable enantiopurity analysis of the entire verubecestat synthetic route using only two chiral columns and mobile phases on a conventional HPLC system, simplifying technical package preparation, method validation and transfer to manufacturing facilities.

Efficient, chemoenzymatic process for manufacture of the Boceprevir bicyclic [3.1.0]proline intermediate based on amine oxidase-catalyzed desymmetrization

The key structural feature in Boceprevir, Merck's new drug treatment for hepatitis C, is the bicyclic [3.1.0]proline moiety "P2". During the discovery and development stages, the P2 fragment was produced by a classical resolution approach. As the drug candidate advanced through clinical trials and approached regulatory approval and commercialization, Codexis and Schering-Plough (now Merck) jointly developed a chemoenzymatic asymmetric synthesis of P2 where the net reaction was an oxidative Strecker reaction. The key part of this reaction sequence is an enzymatic oxidative desymmetrization of the prochiral amine substrate.

The effect of agitated drying on the morphology of l-threonine (needle-like) crystals

Experiments have been carried out to study the behavior of L-threonine (needle-like) crystals during agitated drying. For an L-threonine/water system the morphology of the crystals was monitored using light microscopy and image analysis. Analysis of the transient behavior of the crystal size and shape distribution showed that attrition and agglomeration took place simultaneously during the process. The variation of the operating conditions (temperature, agitation and vacuum) revealed that attrition dominated the drying process when the drying rate was low and/or the shear rate was high. For high drying rates and low shear rates, agglomeration became dominant. This study suggests that crystal redissolution had no significant impact on crystal morphology. It was also found that due to their needle-like shape, large L-threonine crystals were very sensitive to attrition. When attrition controlled the drying process, most of the particle size reduction took place below a critical moisture content of 4%. When agglomeration controlled the drying process, most of the crystal size enlargement occurred below a moisture content of 6%.