Allylic ethers 7a and 7b were used as model substrates, having previously been employed as intermediates en route to delamanid. Screening of a panel of peroxidases and monooxygenases revealed that several P450 BM3 mutants were able to catalyze the target epoxidation reaction (Table ). P450s are known to promote a variety of oxidative pathways such as dihydroxylation and allylic oxidation. Pleasingly, the active enzymes identified displayed complete chemoselectivity, although after extended reaction times degradation to the 4-bromophenol or 4-iodophenol could be observed. The absolute configuration of the major enantiomer was confirmed using chiral HPLC analysis, by comparison to a known synthetic standard (see SI). The bromo derivative 7a was taken forward in subsequent assays, based on the higher initial levels of conversion and enantioselectivity compared to the iodo-substituted alkene 7b (Entries 4 & 5).