Extradiol dehydrogenases are known to convert catechol into muconic semialdehydes. These muconic semialdehydes and their derivatives serve as precursors for the synthesis of nylon and other key building blocks. However, catechol derivatives are unstable, have limited commercial availability, and are challenging to synthesize due to the presence of titratable OH groups. Conversely, precursor salicylaldehydes are commercially available, simple to modify by cross-coupling reactions, and can be converted to catechols via the Dakin oxidation. Therefore, optimizing a reaction scheme utilizing salicylaldehydes to produce catechol in vitro can more effectively create valuable precursors. HAPMO (4-hydroxyacetophenone monooxygenase), was found to perform a non-native Dakin reaction on 4-fluorosalicylaldehyde to make 4-fluorocatechol. However, no other substrates have been tested in this reaction, and no downstream reactions have been demonstrated. We have found that, when used in an enzymatic cascade with BphC, an extradiol dehydrogenase, HAPMO can be used to create muconic semialdehydes. In this work, we are optimizing semialdehyde production, and screening different salicylaldehydes in the reaction, with a particular focus on preparative scale conditions. Preliminary results suggest that this can be reasonably achieved with wild type HAPMO. These findings will be leveraged to further explore the utility of these catalysts for building block synthesis.
