An unnatural tricyclic oxaterpenoid, obtained by treatment of the sesquiterpene synthase presilphiperfolan-8 beta-ol synthase (BcBOT2) with an unnatural farnesyl pyrophosphate ether derivative, itself obtained by chemical synthesis, was converted in oxidation studies as part of a broad screening program by selected unspecific peroxygenases (UPOs). Product analysis revealed that Agrocybe aegerita UPO, its mutant PaDa-I, and two commercial ones, UPO54 and UPO49, provided new oxidation products with sufficient efficiency for subsequent upscaling that allowed product isolation and structure elucidation. As such new terpene-based oxiranes and hemiacetals were formed by UPO-mediated epoxidations and CH-activation. The structure elucidation was further supported by comparison with products generated by chemical oxidation. The unnatural tricyclic sesquiterpenoid, synthesized from an ether-modified farnesyl pyrophosphate using the sesquiterpene synthase (BcBOT2), was oxyfunctionalized by various unspecific peroxygenases (UPOs). UPO54 and UPO49 catalyzed epoxidations and regioselective hydroxylations, leading to four new terpene-based oxiranes and hemiacetals, thus expanding the "terpenome" and the potential of unique flavors and fragrances. All products were successfully isolated, and their structures were elucidated. image