Albumin-catalysed synthesis of flavanones

Abstract

Flavanones are a family of phytochemicals that have regained importance over the last decade due to their diverse biological activity. The conventional building of the flavanone skeleton is accomplished through a Claisen-Schmidt condensation followed by an intramolecular oxa-Michael addition, but the involved strong basic pH favours side reactions and affects flavanone yield. This work presents a mild access to flavanones based on a sustainable catalyst, bovine serum albumin (BSA), which is a promiscuous protein. BSA catalysed the reaction between a set of 2 ´ -hydroxyacetophenones and benzaldehydes in methanol at 60 °C to give the corresponding flavanones in 58–90% conversions. Experiments showed that BSA promotes the Claisen-Schmidt step as well as accelerates the subsequent oxa-Michael addition. Besides, BSA-catalysed reaction of acetophenone and benzaldehyde was studied, which afforded the Michael adduct 1,3,5-triphenylpentane-1,5-dione (85% conversion). On the whole, the herein reported results expand the potential of BSA as a mild and sustainable catalyst in organic synthesis.