Phenolic oxidation of 1, 2, 3, 4-tetrahydro-6, 7-dihydroxy-1-(4-hydroxy-3-methoxyphenethyl)-2-methylisoquinoline (14) with ferric chloride gave the homoproaporphine (15), isolated as the corresponding diacetate (16), which would be a key intermediate to kesselringine (6) from chemical and biogenetic points of view.
