Carbapenems as water soluble organocatalysts [version 1; referees: 2 approved]

Abstract

Background: Identification of organocatalysts functioning in aqueous environments will provide methods for more sustainable chemical transformations and allow tandem reactions with biocatalysts, like enzymes. Here we examine three water-soluble carbapenem antibiotics (meropenem, doripenem, and ertapenem) as secondary amine organocatalysts in aqueous environments. Methods: The Michael addition of nitromethane to cinnamaldehyde was used as the model reaction. The reactions were monitored by 1H NMR, and the enantioselectivity was determined by chiral HPLC. Results: The effects of buffer components, pH, organic co-solvents and anchoring into a protein scaffold were investigated. Moderate yields of the Michael addition were obtained in buffer alone. The use of methanol as a co-solvent in a ratio of 1:1 increases the yield by 50%. Anchoring of the catalysts into a protein backbone reverses the enatioselectivity of the reaction. Conclusions: Despite only moderate yields and enantioselectivities being obtained, this study lays the foundations for future development of efficient organocatalysis in aqueous environments.