Proof of formation of an unstable conjugated triene on decomposition of gibberellin A3 in water
It has been shown by the methods of1H 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 λmax 326 nm is formed which is readily converted into allogibberic acid and is isolated as a mixture (1:2) with this acid. In the1H 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.
Ein Beitrag zur Photochemie des singulett-angeregten 5-MethyIencyclohexa-1,3-dien-Systems / A Contribution to the Photochemistry of the Singlet Excited 5-Methylenecyclohexa-1,3-diene System
Abstract 5-Methylenecyclohexa-13-diene System, S, Excitation, Isomerizations 1,2,3,4,6-Pentamethyl-5-methylenecyclohexa-1,3-diene and 1,2,3,4,6,6-Hexamethyl-5-methy-lenecyclohexa-1,3-diene have been synthesized. The isomerizations following singlet excitation have been studied.
Plant hormones—V.
Abstract Thin-layer chromatographic data in five solvent systems are presented which enable the separation of the seventeen known gibberellins. The Rf values are not reproducible and cannot be standardized. They can only be used for positive identification in conjunction with authentic samples. All seventeen gibberellins can be separated and identified by gas-liquid chromatography of the methyl esters and trimethyl silyl ethers of the methyl esters on 2% QF-1 and 2% SE-33 columns. The retention times can be standardized. These methods have been applied to the crude acidic extract from immature seed of Phaseolus multiflorus and indicate the presence of gibberellins A1, A4, A5, A6, A8, and A13. In subsequent column chromatography of the crude extract, gas-liquid chromatography showed the presence of gibberellins A1, A5, A6 and A8 in the appropriate fractions, eluted with the expected percentage of acetone in water.