Intramolecular transesterification of depsides yields fluorescent 1H-isochromen-1-ones: Application as a chemical probe for lichen determination

S Ferron (1) , P Jéhan (2) , X Guillory (1, 3) , P Uriac (1)

1 ISCR - Institut des Sciences Chimiques de Rennes
2 ScanMAT - Synthèse Caractérisation Analyse de la Matière
3 OSS - Oncogenesis, Stress, Signaling

The reactivity of eight purified depsides obtained from six european lichens and that display as 2-oxoalkyl chain in ortho-position of the ester bond was explored. These depsides were found to lead to 1H-Isochromen-1-ones, which exhibit a distinctive blue fluorescence at 365 nm, in the presence of a 10% aqueous solution of KOH. A mechanistic explanation, involving the formation of an enolate intermediate and intramolecular transesterification, was proposed and validated by DFT. By exploiting this fluorescent phenomenon, we conceived a chemical probe (the KUV probe) that is useful for lichen determination, as exemplified on a selection of European Porpidia species.

Mots clés: Chemical lichen determination; Depsides; Enolate; Fluorescent 1H-isochromen-1-ones; KUV probe; Transesterification; δ-keto esters

Domaines: Chimie

S Ferron, P Jéhan, X Guillory, P Uriac. Intramolecular transesterification of depsides yields fluorescent 1H-isochromen-1-ones: Application as a chemical probe for lichen determination. Phytochemistry, 2022, 198, pp.113139. ⟨10.1016/j.phytochem.2022.113139⟩. ⟨hal-03632050⟩