No abstract

A scalable process has been developed for the synthesis of trans-2-methylcyclopropanecarboxylic acid via the stereoselective cyclopropanation of ethyl crotonate with dimethylsulfoxonium methylide (Corey's ylide). This well-known reaction is generally low yielding and very challenging to scale up as it involves highly reactive reagents. A design of experiment (DoE) allowed us to quickly define the optimal ranges for the reaction parameters. A very significant increase of the yield was obtained by adding the ylide to ethyl crotonate in DMSO at 80 °C in anhydrous conditions. In view of a scale-up at a multikilogram scale, several experiments were then performed combining Process Analytical Technologies (PAT) and Calorimetry (Dynamic DSC, Adiabatic Reaction Calorimetry and Vent Sizing Package). For safety reasons at high temperatures on large scale the reaction was also evaluated in a continuous flow reactor. Thanks to these studies, we were able to develop an efficient process avoiding the hazardous accumulation of the thermally unstable dimethylsulfoxonium methylide.

The Process Analytical Technology initiative and Quality by Design paradigm have led to changes in the guidelines and views of how to develop drug manufacturing processes. On this occasion the concept of the design space, which describes the impact of process parameters and material attributes on the attributes of the product, was introduced in the ICH Q8 guideline. The way the design space is defined and can be presented for regulatory approval seems to be left to the applicants, among who at least a consensus on how to characterize the design space seems to have evolved. The large majority of design spaces described in publications seem to follow a “static” statistical experimentation and modeling approach. Given that temporal deviations in the process parameters (i.e., moving within the design space) are of a dynamic nature, static approaches might not suffice for the consideration of the implications of variations in the values of the process parameters. In this paper, different forms of design space representations are discussed and the current consensus is challenged, which in turn, establishes the need for a dynamic representation and characterization of the design space. Subsequently, selected approaches for a dynamic representation, characterization and validation which are proposed in the literature are discussed, also showcasing the opportunity to integrate the activities of process characterization, process monitoring and process control strategy development.

No abstract

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.