Expanding the Bio-Based Sunscreen Library: Rapid, Atom-Efficient Synthesis of Lignocellulose-Derived UV Filters

Abstract

Herein, we report a rapid and efficient methodology for the synthesis of Claisen-Schmidt adducts from cellulose-derived Cyrene and a range of biomass-derived aromatic aldehydes. Using a catalytic amount of NaOH in ethanol, the condensations were completed in only 30 min, representing a dramatic reduction in reaction time compared with previous protocols that require prolonged heating, while delivering yields in the range of 70–90%. The reaction proved effective even with electron-rich methoxy-substituted benzaldehydes and cinnamaldehyde derivatives. Selected products were evaluated for their UV-filtering performance, and the cinnamaldehyde-derived adducts exhibited particularly promising activities. Computational toxicity and ecotoxicity assessments predicted a favorable safety profile for the p-methoxy cinnamaldehyde derivative (1S,5R,E)-3-((E)-3-(4-methoxyphenyl)allylidene)-6,8-dioxabicyclo[3.2.1]octan-4-one, while the synthetic methodology was shown to be environmentally sustainable. Overall, this work demonstrates a synergistic strategy for upgrading cellulose- and lignin-derived feedstocks into high-value UV-filtering compounds with potential applications in sun care formulations.