The monoterpene citronellol often represents the substrate for the synthesis of other natural products and fragrances bearing α-branched tetrahydropyran moieties. In this contribution, we developed a process that combines in one-pot condition photocatalytic Schenck-ene reaction and biocatalytic halocyclization to synthesize enantiopure α-branched tetrahydropyrans starting from natural monoterpene citronellol. The reaction pathway of the enzymatic haloetherification, studied by combining experimental and theoretical studies, showed for the first time the key role played by the hydroperoxide functional group in the control of the regioselectivity of the cyclization step. Overall, a novel and sustainable synthetic procedure is reported as a new approach for α-branched tetrahydropyrans.

A photochemoenzymatic halodecarboxylation of ferulic acid was achieved using vanadate-dependent chloroperoxidase as (bio)catalyst and oxygen and organic solvent as sole stoichiometric reagents in a biphasic system. Performance and selectivity were improved through a phase transfer catalyst, reaching a turnover number of 660.000 for the enzyme.