Synthesis and structural reassignment of (+)-epicalyxin F

We have established the structure of (+)-epicalyxin F through chemical synthesis. An acid-promoted rearrangement of synthetic benzopyran 6 led to the identification of the natural product as (3S,5S,7R)-epicalyxin F (22). Comparison with NMR spectra and optical rotation of the natural product confirms our assignment, and the reassigned structure is compatible with the proposed biosynthetic pathway.