Sustainable Straightforward Synthesis and Evaluation of the Antioxidant and Antimicrobial Activity of Sinapine and Analogues
Louis M. M. Mouterde, Aurélien A. M. Peru, Matthieu M. Mention, Fanny Brunissen, Florent Allais
Abstract
Naturally occurring sinapine was successfully synthesized through a proline-mediated Knoevenagel–Doebner condensation in ethanol. This synthetic process involving biobased syringaldehyde, Meldrum’s acid, and choline chloride offers a sustainable alternative to the existing low-yield pathways. This two-step strategy gives access to sinapine in a 52% overall yield and has been implemented in the synthesis of sinapine analogues, using 4-hydroxybenzaldehyde, 3,4-dihydroxybenzaldehyde, and vanillin as precursors, giving target molecules with 34–61% overall isolated yields. The purity of synthetic sinapine and its analogues (ca. 95%) was assessed by NMR and high-performance liquid chromatography—mass spectrometry analyses. Furthermore, the antioxidant and antimicrobial activities were assessed, and the potential of this series of molecules was confirmed.