STRUCTURES, SYNTHESES, AND CHEMOTAXONOMIC SIGNIFICANCE OF SOME NEW ACETOPHENONE DERIVATIVES FROM ENCELIA-FARINOSA GRAY

The resinous exudate of brittle bush (Encelia farinosa Gray) contains a number of substituted benzofurans and chromenes. All appear to arise from the biogenic prenylation of resacetophenone. The chromene compounds constitute a remarkable sequence of reduction states of encecalin (3) and represent important chemotaxonomic indicators. All the compounds have been characterized on the basis of spectral and chemical methods. A new general synthesis of dimethylchromene derivatives from resorcinol is described. © 1979, American Chemical Society. All rights reserved.