Permethylaryl ether diacetates

The natural occurrence and synthesis of a novel class of C-ring isomerized oligomeric flavanoids, termed phlobatannins, was demonstrated some twelve year ago (111, 112). These 3,4,9,10-tetrahydro-2if,8//-pyrano[2,3-/]chromenes, e.g. (104), are characterized by the liberated resorcinol moieties from the A/C-ring arrangement of the parent biflavanoid, e.g. (24), and by the conspicuous absence of the effects of dynamic rotational isomerism in the NMR spectra of their permethylaryl ether diacetates at ambient temperatures. 

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