Natural acetylenes. Part XXV. The biosynthesis of benzenoid polyacetylenes

Both [1-14C]- and [2-14C]-acetate have been fed to Dahlia plants and the radioactive benzenoid polyacetylene Ph·[CC]2·CHCHMe isolated. Its selective degradation revealed a uniform labelling of alternate carbon atoms in the side-chain with the terminal methyl group derived from the methyl group of acetate and a benzene ring activity which, although not located, also agrees with an alternating labelling of its carbon atoms.Chodkiewicz coupling has been used to improve the syntheses of the cis- and trans-isomers of the phenyl-heptenediyne and osmium tetroxide oxidation to convert them into the erythro- and threo-isomers of the diol Ph·[CC]2·CH(OH)·CHMe·OH.