A Bio‐Based Chiroptical Overcrowded Alkene From Flavanone: Photoreactivity and Theoretical Investigation

The design of light-driven overcrowded alkenes often relies on complex synthetic strategies to achieve precise control over rotational motion. In this study, we demonstrate a sustainable approach to design an overcrowded alkene and an O-heterocyclic phenanthrene derivative using a bio-based enantiopure flavanone, (-)-isolonchocarpin, as starting material. The synthesis involves a McMurry deoxygenative homocoupling reaction to generate a sterically hindered overcrowded alkene, which can further undergo photochemical (E/Z)-isomerization and oxidative 6π-electrocyclization. The oxidation product was shown to have emission properties, highlighting the potential of synthesizing bio-based chromophoric compounds in minimal steps. Computational studies using spin-flip time-dependent density functional theory (SF-TDDFT) reveal that the inherent chirality of the starting material induces asymmetry in the rotational pathway, biasing the directionality of motion. By integrating enantiopure natural products into functional photoresponsive materials, this work offers a more sustainable route to develop new bio-based photoresponsive molecular machines while deepening our understanding of chirality-driven motion in dynamic systems.