Nucleoside/nucleobase chemical synthesis
Finally found what I was looking for, especially paired with Mithoron's comments.

"Currently, purine nucleotides are obtained at industrial level mainly by microbial fermentation".

https://microbialcellfactories.biomedcentral.com/articles/10.1186/s12934-015-0234-4

Ledesma-Amaro, Rodrigo &amp; Jiménez, Alberto &amp; Santos, María de los Ángeles &amp; Revuelta, José. (2013). Biotechnological production of feed nucleotides by microbial strain improvement. Process Biochemistry. 48. 1263-1270. 10.1016/j.procbio.2013.06.025.