SYNTHESIS OF CROWN-ETHERS RELATED TO UBIQUINONES

Crown ethers in which the two methoxy groups of ubiquinone-0 (2,3-dimethoxy-5-methyl-1,4-benzoquinone) are replaced by oligoethylene glycol bridges have been obtained in five straightforward steps in 35-40% overall yield from 5-methylpyrogallol. A Fremy salt oxidation of a phenolic precursor is used in the final step. The further elaboration of crown ether analogues of ubiquinone-2 was achieved by enol geranylation of cyclopentadiene adducts of the former quinones and subsequent retro-Diels-Alder reaction. The Claisen rearrangement of 2,2-dimethoxy-5-methylphenyl allyl ethers and related crown ethers affords ortho- and para-allyl-substituted phenols (3:1) that are oxidized to give bisnorubiquinone derivatives and their ortho- quinone isomers. All new compounds are characterized by high resolution NMR and mass spectrometry.