Aryllead-Mediated Synthesis of Linear 3-Arylpyranocoumarins: Synthesis of Robustin and Robustic Acid.

The two naturally occurring linear 3-arylpyranocoumarins, robustin 1 and robustic acid 2, have been synthesised in nine steps from methyl 2,4,6-trihydroxyphenyl ketone, in 19% overall yield for robustin and 18% for robustic acid. Their syntheses involved, as a key step, the regioselective arylation of a functionalised 4-hydroxybenzo[l,2-b : 5,4-b′]dipyran-2-one with the appropriate aryllead triacetate.