PROOF OF FORMATION OF AN UNSTABLE CONJUGATED TRIENE ON DECOMPOSITION OF GIBBERELLIN A3 IN WATER

Article abstract of DOI:10.1007/BF00633396

It has been shown by the methods of 1H NMR and high-performance liquid chromatography with recording of UV spectra that in aqueous solutions of gibberellin A₃, via gibberellenic acid, an unstable conjugated triene having λ_max 326 nm is formed which is readily converted into allogibberic acid and is isolated as a mixture (1:2) with this acid.In the 1H NMR spectrum of the triene, confirming its structure, spin-spin coupling both of the H-5 proton and of the protons of the methyl group with all the H-1, H-2, and the H-3 protons is observed.The precursor of allogibberic acid has been ascribed the structure of (-)-13-hydroxy-19,20-dinorgibberella-1,3,9,16-tetraen-7-oic acid with a conjugated 1,3,9-trienic system.