Reagent-free continuous thermal tert-butyl ester deprotection.

Continuous processing enables the use of non-standard reaction conditions such as high temperatures and pressures while in the liquid phase. This expands the chemist's toolbox and can enable previously unthinkable chemistry to proceed with ease. For a series of amphoteric amino acid derivatives, we have demonstrated the ability to hydrolyze the tert-butyl ester functionality in protic solvent systems. Using a continuous plug flow reactor at 120-240°C and 15-40min reaction times, no pH modification or additional reagents are needed to achieve the desired transformation. The method was then expanded to encompass a variety of more challenging substrates to test selectivity and racemization potential. The acid products were generally isolated as crystalline solids by simple solvent exchange after the deprotection reaction in good to high yield and purity.

Kilogram-scale prexasertib monolactate monohydrate synthesis under continuous-flow CGMP conditions.

Advances in drug potency and tailored therapeutics are promoting pharmaceutical manufacturing to transition from a traditional batch paradigm to more flexible continuous processing. Here we report the development of a multistep continuous-flow CGMP (current good manufacturing practices) process that produced 24 kilograms of prexasertib monolactate monohydrate suitable for use in human clinical trials. Eight continuous unit operations were conducted to produce the target at roughly 3 kilograms per day using small continuous reactors, extractors, evaporators, crystallizers, and filters in laboratory fume hoods. Success was enabled by advances in chemistry, engineering, analytical science, process modeling, and equipment design. Substantial technical and business drivers were identified, which merited the continuous process. The continuous process afforded improved performance and safety relative to batch processes and also improved containment of a highly potent compound.