An Ehrlich-inspired retrobiosynthesis of pharmaceutical scaffolds

Brewer’s yeast ( Saccharomyces cerevisiae ) acquires nitrogen from branched-chain and aromatic amino acids via the Ehrlich pathway, generating flavor (fusel) byproducts. Recently, diverting 4-hydroxyphenylacetaldehyde from Ehrlich catabolism of ʟ-tyrosine has enabled microbial production of opioids and other plant benzylisoquinolines. Yet, fusel metabolism is versatile in substrate scope, offering an untapped entry point for synthesizing structurally diverse aldehydes. Here, we repurpose the yeast Ehrlich pathway into a modular biocatalytic conduit for manufacturing privileged pharmaceutical alkaloids. We utilize retrobiosynthetic analysis and enzyme screening to derive scaffolds representative of solifenacin, colchicine, and ephedrine pharmaceuticals from simple amino acids. We survey wild yeasts for catabolism of ʟ-phenylglycine and demonstrate Ehrlich conversion to benzyl alcohol or ( R )-phenylacetylcarbinol by 29 strains across nine genera. Implementing an ω-transaminase enables production of norephedrine from a simple amino acid input. This work unveils a generalizable biocatalytic route to clinically important alkaloids by exploiting metabolic logic from a yeast flavor pathway.