(Z)-1-Hydroxy-3-(3′-hydroxyphenyl) prop-2-enes undergo phenolic oxidation by phenyliodonium diacetate (PIDA) in methanol to give 8a-methoxy-2H, 6H-dihydrochromen-6- ones. These are reduced by DIBAL-H to 2-substituted-Δ3, 4-chromenes, the overall process being a unique heterocyclic synthesis in which the heteroatom is not initially attached to a benzene ring, but is introduced from a side chain. Parallel oxidations using cis-l-hydroxy-3 ...