Synthetic Studies on Gibberellins

A. Synthesis of Methyl-2 methoxy-8 methylene-10beta methyl 4b(alpha)H- gibba- A- triene- l carboxylate. A. synthetic route to gibberellin A4 with the potential of being adapted to the synthesis of gibberellic acid has been investigated. Terracinoic acid, a degradation product of terramycin, has been elaborated to methyl-2 methoxy-8 methylene-10beta methyl-4b(alpha)H-gibba-A-triene-1 carboxylate a tetracyclic compound in which rings B and C have the un-natural trans-fusion (i. e. epimeric at 4b). The stereochemistry of this tetracyclic compound has been deduced from a. study of the N.M.R. spectra of related compounds. A preliminary investigation into the possibility of adapting this route to the synthesis of rings C and D of gibberellic acid has been made. Attempts have been made unsuccessfully to functionalise an unactivated methyl group in terracinoic acid and a variety of derivatives. B. Synthesis of Indane-1,7-Dicarboxylic Acid. A possible synthetic route to the AB ring system of several gibberellins has been investigated. Benzaldehyde was converted to indane-1,7-dicarboxylic acid in a ten step synthesis but the route was abandoned at this point because of poor yields in an internal Friedel-Crafts acylation step