Benchtop 19F nuclear magnetic resonance spectroscopy enabled kinetic studies and optimization of the synthesis of carmofur

Carmofur, a 5-fluorouracil derivative, was initially developed as an antineoplastic agent to treat colorectal cancer. Through drug repurposing efforts, it has been identified as a potent covalent inhibitor of the main protease of SARS-CoV-2 (Mpro), making it a promising therapeutic agent against COVID-19. However, previous synthetic procedures suffer from low yields, or long reaction times. In this study, benchtop 19F nuclear magnetic resonance spectroscopy (NMR) enables the real-time quantitative monitoring and characterization of the synthesis of carmofur by providing kinetic insight. Furthermore, its proton lock capabilities no longer require the use of deuterated solvents, and has enabled convenient, and rapidly scalable synthesis of our compound. Here, we present the application of benchtop 19F NMR as an efficient method for optimizing the synthesis of carmofur and its future application in the synthesis of related 5-FU analogs.