Reaction of 2',5'-dihydroxyacetophenone (I) with dihydropyran (II) and pyridinium p-toluenesulfonate gives the protected bis-tetrahydropyranyl ether (III), which is submitted to Claisen-Schmidt condensation with 2-chlorobenzaldehyde (IV) in the presence of barium hydroxide, yielding the chalcone (V). Finally, the tetrahydropyranyl protecting groups of (V) are removed by acidic hydrolysis with p-toluenesulfonic acid in MeOH.