Diploicin manganese dioxide oxidation

A number of intramolecular variations are documented, some of biogenetic interest. The benzophe-none (224) was cyclized in good yield (83%) to 2,6-dihydroxyxanthone (225) with ferricyanide," and the synthetic depside (226) yielded diploicin (227) on manganese dioxide oxidation." Finally the di-a lheptanoid (228) afforded the macrocyclic ether (229) on reaction with thallium tristrifluoroacetate similar ethers, e.g. acerogenin, occur naturally. ... 

In the synthesis of diploicin, 3,4-dichloro-4-0-benzylorsellinic acid (74) is esterified with 2,4-dichloroorcinol (75) in the presence of trifluoroacetic anhydride to (76), this product is oxidized to (77) with manganese dioxide, and this methylated and catalytically hydrolyzed to diploicin (78). 

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