Unlocking enzymatic deracemization of structurally diverse allenes by designed photoenzymes

Precise three-dimensional arrangements of atoms and functional groups govern molecular reactivity and biological function, making stereocontrol a central goal in modern organic and medicinal chemistry. Yet reconciling broad substrate generality with high enantioselectivity remains a core limitation of enantioselective catalysis, motivating the pursuit of privileged chiral catalysts. Here we design a new-to-nature photoenzyme that unlocks enzymatic deracemization of structurally diverse allenes, an entropically disfavored process inaccessible to natural biocatalysts. Structure-guided design created substrate-specific interaction networks, delivering high enantioenrichment for axially chiral allenic carboxylic acids, esters, and amides via triplet energy transfer under aerobic conditions. X-ray crystal structures of enzyme–substrate complexes reveal tailored chiral pockets that accommodate distinct substrates and direct enantiocontrol, rationalizing the breadth and selectivity observed. This work reconciles generality with high selectivity on an enzymatic platform, establishes deracemization as an evolvable route to axially chiral molecules, and broadens activation strategies for stereochemical editing. Reconciling broad substrate generality with high enantioselectivity remains a core limitation of enantioselective catalysis. In this study, the authors design a new-to-nature photoenzyme that unlocks enzymatic deracemization of structurally diverse allenes, an entropically disfavored process inaccessible to natural biocatalysts.