In summary, we have developed an efficient biocatalytic synthesis of N-hydroxy-cytidine 4, a key intermediate for the production of Molnupiravir 1. The process takes advantage of an engineered cytidine aminotransferase and benefits from dynamic product crystallization to provide a scalable and sustainable manufacturing route to an important molecule in the fight against Covid-19. Through rounds of directed evolution we were able to achieve the target metrics initially set, namely to operate at [S] > 100 g/L with 90% conversion in 24h. Remarkably this engineered biocatalyst is able to achieve TON >10 which places it within the sphere of well-established industrial biocatalysts of proven utility . Given that selective 5'-acylation of N-hydroxy-cytidine can be achieved with lipases , this work establishes an integrated biocatalytic strategy for Molnupiravir synthesis using cytidine as an inexpensive and readily available starting material.