Sanctis A–C: Three Racemic Procyanidin Analogues from The Lichen <i>Parmotrema sancti‐angelii</i>

Abstract

The phytochemical investigation of the lichen Parmotrema sancti‐angelii afforded three racemic compounds, sanctis A–C, which feature an original dibenzo‐2,8‐dioxabicyclo[3.3.1]nonane scaffold. These compounds were structurally characterized by extensive NMR spectroscopy analyses, comparison between experimental and theoretical NMR spectroscopic data, and X‐ray crystallography. These metabolites are similar to procyanidin A and display a methyl group instead of a pendant aromatic ring at C‐9, a so far unprecedented structural feature. A biosynthetic route to sanctis A–C is proposed.