Search

The structures of five new natural products (GB 27-GB 31, 1-5), isolated as minor components from the bark of Galbulimima baccata, have been determined by 2D NMR spectroscopy in combination with DFT calculations. Among the alkaloids, GB 31 (5) belongs to Class I, GB 27 (1) and 28 (2) belong to Class II, and GB 30 (4) belongs to Class III GB alkaloids. GB 31 is the first non-nitrogen-containing GB "alkaloid", being a biosynthetic oxidation product of himbacine, himandravine, or himbeline. GB 29 (3) has an entirely new natural product scaffold but belongs to Class IV (miscellaneous alkaloids). The isolation of a new Galbulimima scaffold has revealed a new pathway in the biosynthesis of the GB alkaloids. The new molecules isolated have shed further light on the biogenetic relationship among these structurally unique and complex groups of alkaloids. We present, for the first time, a unified biogenesis for the GB alkaloids that were first isolated in the 1950s and now number over 40 examples. This work also brings full circle the story of Galbulimima alkaloids. A life-long project of Wal Taylor involving one of his first students (Lew Mander) and one of his last students (Peter Karuso), a story stretching over six decades, has come to a final conclusion.

Gibberellins (GAs) are essential phytohormones involved in numerous aspects of plant growth and development. Notably, the biochemistry and genetics of GA biosynthesis, which is associated with their endogenous regulation, have been largely resolved; however, a crucial unsolved question remains: the precise mechanism of the stepwise oxidation and subsequent removal of C-20 from C20 precursors, leading to bioactive C19 gibberellins, is still unresolved. To satisfy numerous requests from biologists, practical preparations of certain GAs that were isolated in miniscule quantities are highly demanded. Herein, we report the first practical syntheses of GA15 and GA24, the key C20 metabolites in gibberellin biosynthesis, from commercially available GA3. The protocols are robust and offer the capacity to produce GA24 and GA15 under gram scales in high overall yields and thus aid in further biological and related studies.

Endogenous gibberellins (GAs) and GA-related compounds at two different developmental stages of apple seeds(Malus domestica cv. McIntosh) were analyzed by gas chromatography-mass spectrometry.From the seeds at ca. 10 and/or 14 weeks after full-bloom, the following GAs and 9,15-cyclogibberellins (9,15-cyclo-GAs) were identified by a comparison of their mass spectra and Kovats retention indices with those of authentic specimens: GA4, GA7, GA9, GA12, GA17, GA19, GA20, GA25, GA34, GA35, GA45,GA53, GA54, GA61, GA62, GA63, GA70, GA73, GA80, GA84, GA88, 3-epi-GA4, 3-epi-GA54, and 3-epi-GA63, 9,15-cyclo-GA9, lβ-hydroxy-9,15-cyclo-GA9, 2β-hydroxy-9,15-cyclo-GA9, 3α-hydroxy-9,15- cyclo-GA9, 3β-hydroxy-9,15-cyclo-GA9, and llβ-hydroxy-9,15-cyclo-GA9. The major components in the seeds at ca. 10 weeks after full-bloom were GA4, GA7, GA9, GA17, GA35, GA54, GA62, GA80, and GA84, and those in the seeds at ca. 14 weeks after full-bloom were GA17, GA25, GA45, GA62, GA63, GA80,GA84, 9,15-cyclo-GA9, and 1β-, 3β-, and 11β-hydroxy-9,15-cyclo-GA9. New GA number (GA103 _ 108) have been allocated to 9,15-cyclo-GA9, and 1β-, 2β-, 3β-, 3α-, and 11β-,hydroxy-9,15-cyclo-GA9, respectively (1β- and 3α-hydroxy-9,15-cyclo-GA9 were identified previously as fern anteridiogens, although GA numbers have not previously been assigned to these compounds). This is the first report of the co-occurrence of GA73 and 9,15-cyclo-GAs in higher plants.

The following gibberellins (GAs) and antheridiogens were identified by their mass spectra and Kovats retention indices from combined gas chromatography-mass spectrometry of purified extracts of the prothallia and sporophytes of Anemia phyllitidis, a Schizaeaceous fern: a trace amount of GA9 (4-week-old prothallia); GA9, GA24, GA25, antheridic acid and 3-epi-GA63 (6-week-old prothallia); and GA4, GA9, GA15, GA19, GA20, and GA24 [young sporophytes (younger than one year old) and/or old sporophytes (between one- and two years old). Of these compounds, GA24, GA9, and GA4 were quantified by gas chromatography-selected ion monitoring, using (2)H-GAs as internal standards, and the content of antheridic acid, the principal antheridiogen, was evaluated by a radioimmunoassay which we have developed. The results indicate that endogenous levels of GAs and antheridiogens in prothallia began to increase rapidly between 4 and 6 weeks after sowing, the contents of antheridic acid and GA24, the most abundant GA in 6-week-old prothallia, being 107.4 and 37.9 ng/g fresh weight, respectively. The most abundant GA in the sporophytes was GA9, the content in young and old sporophytes being 15.3 and 7.3 ng/g fresh weight, respectively.

The 1 H and 13 C NMR spectra of camelliagenin A and A1-barrigenol from the seeds of Barringtonia asiatica were completely assigned for the first time by one- and two-dimensional homo- and heteronuclear studies ( 1 H, 13 C, DQCOSY, TOCSY, HMQC, HMBC) at 600 and 150.89 MHz. The article reports standard data that may be important for potential authors needing such information.

Germination of Styrax japonicus seeds is promoted by warm stratification (WS) at 18–20°C followed by cold stratification (CS) at 4–5°. The objective of this work was to analyze the state and mobility of water molecules measured by 1H-NMR and endogenous gibberellins (GAs) and abscisic acid (ABA) by ultra performance liquid chromatography/mass spectrometry/mass spectrometry (UPLC-MS/MS) as influenced by WS and CS treatments had not previously been investigated. Styrax seeds that received 35 days of WS (35D WS) followed by 63 days of CS (63D CS) (35D WS + 63D CS) germinated. Seeds that received only 35D WS failed to germinate. Endogenous GA1, GA8, GA19, GA20, and GA53 were identified as well as GA17, GA23, GA28, GA29, and GA97 by gas chromatography/MS (GC/MS) and UPLC-MS/MS in seeds that were treated with warm and cold stratification (WS + CS). This suggests that the early C-13 hydroxylation pathway [-GA53-(GA44)-GA19-GA20-GA1-GA8] of GAs is a major biosynthetic pathway in the seeds. The concentration of GA53 and GA19 increased following WS and that of GA53 increased after WS + CS. The concentration of GA19 increased only slightly after WS + CS. The concentration of GA1 increased only after WS + CS. ABA concentration significantly decreased following the WS treatment. It is concluded that the mobility of water molecules and water content in cotyledons and endosperm is increased following WS + CS treatments. The occurrence of C-13 hydroxylated GAs suggests that the early C-13 hydroxylation pathway, → GA53 → GA44 → GA19 → GA20 → GA1 → GA8, is a major biosynthetic pathway in Styrax seeds.

The structures of four new alkaloids isolated from the bark of the rain forest trees Galbulimima belgraveana and Galbulimima baccata have been determined by a combination of NMR spectra and single crystal X-ray crystallography. Two of the alkaloids are simple oxygenated derivatives of himbacine, while the remaining two are based on a novel 7,19-cyclo-himbacine skeleton. © 2010 Elsevier Ltd. All rights reserved.

The bacterial phosphotriesterases catalyze hydrolysis of the pesticide paraoxon with very fast turnover rates and are thought to be near to their evolutionary limit for this activity. To test whether the naturally evolved turnover rate could be improved through the incorporation of unnatural amino acids and to probe the role of peripheral active site residues in nonchemical steps of the catalytic cycle (substrate binding and product release), we replaced the naturally occurring tyrosine amino acid at position 309 with unnatural L-(7-hydroxycoumarin-4-yl)ethylglycine (Hco) and L-(7-methylcoumarin-4-yl)ethylglycine amino acids, as well as leucine, phenylalanine, and tryptophan. Kinetic analysis suggests that the 7-hydroxyl group of Hco, particularly in its deprotonated state, contributes to an increase in the rate-limiting product release step of substrate turnover as a result of its electrostatic repulsion of the negatively charged 4-nitrophenolate product of paraoxon hydrolysis. The 8-11-fold improvement of this already highly efficient catalyst through a single rationally designed mutation using an unnatural amino acid stands in contrast to the difficulty in improving this native activity through screening hundreds of thousands of mutants with natural amino acids. These results demonstrate that designer amino acids provide easy access to new and valuable sequence and functional space for the engineering and evolution of existing enzyme functions.

Bisdemethylaaptamine, an alkaloid naphtyridine with molecular weight 200 and formulae molecule C11H8N2O2 has been isolated from Bunaken Marine Park sponge Aaptos sp. Isolation was done by using several stages of column chromatography and high performance liquid chromatography. Molecular weight of this naphtyridine alkaloid was determined by electron ionization (EI) and electrospray ionization (ESI) mass spectroscopies and its structure assigned to be 8,9-dihydroxy-1H-benzo[d,e][1,6]naphtyridine by proton and carbon nuclear magnetic resonances (1H and 13C-NMR). Keywords: Sponge, Aaptos sp., naphtyridine alkaloid, bisdemethylaaptamin

A triterpene ester saponin has been isolated from the seed of Barringtonia asiatica and its structure has been established by extensive application of high-resolution FABMS and two dimensional NMR techniques to be 3-O-{[β-D-galactopyranosyl(1→3)-β-D-glucopyranosyl(1→2)]-β-D-glucuronopyranosyloxy}-22-O-[2-methylbutyroyloxy]-15,16,28-trihydroxy-(3β,15α,16α,22α)-olean-12-ene. Keywords: Barringtonia asiatica, Lecythidaceae, triterpenoid

An antifeedant triterpenoid saponin has been isolated from the seed of Barringtonia asiatica and its structure elucidated mainly by two dimensional NMR spectroscopy is identified as 3-O-{[β-D-galactopyranosyl(1→3)-β-D-glucopyranosyl (1→2)]-β-D-glucuronopyranosyloxy}-22-O-[2-(E)-methyl-2-butenyloyloxy]-15, 16,28-trihydroxy-(3β,15α,16α,22α)-olean-12-ene. This compound showed antifeedant activity towards Epilachna sp larvae Keywords: Barringtonia asiatica, saponin, antifeedant

The structures of three new alkaloids isolated from the bark of the rain forest tree Galbulimima belgraveana , have been determined by a combination of NMR spectroscopy and X-ray crystallography. One of the alkaloids, himgrine ( 5 ), was shown to be an oxygenated derivative of himbacine ( 1 ), while the second, GB16, ( 8 ) proved to be identical with a degradation product from himgaline ( 4 ). The remaining alkaloid, GB17 ( 12 ) possesses an entirely new and unexpected skeleton.

Three new 11β-hydroxy C20 gibberellins have been isolated from immature loquat fruit and their structures were established as 11β-hydroxy-GA12, 11β-hydroxy-GA15 and 11β-hydroxy-GA53, respectively, by direct GC–MS comparisons with authentic samples obtained from gibberellic acid by multistep syntheses. An advanced intermediate (30) was prepared in 20 steps from which 6 11β-hydroxy C20 gibberellins were prepared by parallel routes involving up to a further 5 steps for each sequence. The key steps involved a much improved synthesis of gibberellenic acid derivatives, a Lewis acid catalysed cyclisation of a diazoketone, a domino-hydroboration of a diene and oxidative cleavage of a ketone derived enolate.

The sequence of Gid1 (a gene for a gibberellin (GA) receptor from rice) was used to identify a putative orthologue from barley. This was expressed in E. coli and produced a protein that was able to bind GA in vitro with both structural specificity and saturability. Its potential role in GA responses was investigated using barley mutants with reduced GA sensitivity ( gse1 mutants). Sixteen different gse1 mutants each carried a unique nucleotide substitution in this sequence. In all but one case, these changes resulted in single amino acid substitutions, and, for the remaining mutant, a substitution in the 5' untranslated region of the mRNA is proposed to interfere with translation initiation. There was perfect linkage in segregating populations between new mutant alleles and the gse1 phenotype, leading to the conclusion that the putative GID1 GA receptor sequence in barley corresponds to the Gse1 locus. Determination of endogenous GA contents in one of the mutants revealed enhanced accumulation of bioactive GA 1 and a deficit of C 20 GA precursors. All of the gse1 mutants had reduced sensitivity to exogenous GA 3 and to AC94377 (a GA analogue) at concentrations that are normally ‘saturating‘, but, at much higher concentrations, there was often a considerable response. The comparison between barley and rice mutants reveals interesting differences between these two cereal species in GA hormonal physiology.

[Structure: see text] A formal total synthesis of diisocyanoadociane, a marine diterpenoid with potent antimalarial properties, has been completed. The synthesis begins with a phenanthrenoid precursor that is transformed into a pyrene-derived intermediate by means of an intramolecular Michael reaction. Nitrogen functionality is introduced via a double Curtius reaction.

The recessive tall rice (Oryza sativa) mutant elongated uppermost internode (eui) is morphologically normal until its final internode elongates drastically at the heading stage. The stage-specific developmental effect of the eui mutation has been used in the breeding of hybrid rice to improve the performance of heading in male sterile cultivars. We found that the eui mutant accumulated exceptionally large amounts of biologically active gibberellins (GAs) in the uppermost internode. Map-based cloning revealed that the Eui gene encodes a previously uncharacterized cytochrome P450 monooxygenase, CYP714D1. Using heterologous expression in yeast, we found that EUI catalyzed 16α,17-epoxidation of non-13-hydroxylated GAs. Consistent with the tall and dwarfed phenotypes of the eui mutant and Eui-overexpressing transgenic plants, respectively, 16α,17-epoxidation reduced the biological activity of GA4 in rice, demonstrating that EUI functions as a GA-deactivating enzyme. Expression of Eui appeared tightly regulated during plant development, in agreement with the stage-specific eui phenotypes. These results indicate the existence of an unrecognized pathway for GA deactivation by EUI during the growth of wild-type internodes. The identification of Eui as a GA catabolism gene provides additional evidence that the GA metabolism pathway is a useful target for increasing the agronomic value of crops.

The initial products from the cyclisation of hexahydrophenanthryl diazo ketones with participation by either the alkene bonds or the aromatic ring (Ar 1,4 ) undergo rearrangement by 1,2 bond shifts or unexpected bond fission. Benzocyclo-octanyl ketones were formed from the latter process.

Rapid access to the ABCE ring system of the C-20 diterpene alkaloids was achieved by silver (I) promoted intramolecular Friedel-Crafts arylation of a functional group specific 5-bromo-3-azabicyclo[3.3.1]nonane derivative. (c) 2005 Elsevier Ltd. All rights reserved.

Shoot branching and plant height are among the key factors that define the overall architecture of plants. We found that overexpression of a cDNA for a zinc-finger protein of petunia, designated Lateral shoot-Inducing Factor (LIF), in transgenic petunia plants resulted in a dramatic increase in lateral shoots and reduced plant height. LIF overexpression also caused a decrease in the number of cells in the stem, leaf, and flower, accompanied by enlargement of cells. trans-Zeatin was decreased while N6-(Delta2-isopentenyl)adenine was increased in the leaves of LIF-overexpressed petunia. Most of the riboside, ribotide, and glucoside forms were also increased. Expression analysis using a LIF::GUS fusion gene and RT-PCR suggested that LIF is specifically expressed around the bases of axillary buds and weakly in basal part of flowers in wild-type petunia. GFP-LIF-GUS fusion proteins were translocated into the nucleus when transiently expressed in onion epidermal cells. LIF overexpression resulted in enhanced branching also in tobacco and Arabidopsis, indicating the conservation of the response to LIF overexpression among dicotyledonous plants. On the basis of these results we discuss about possible functions of LIF.

Bisdemethylaaptamine ( 6 ), a proposed biosynthetic precursor of the aaptamines has been isolated from an Aaptos sp. marine sponge harvested off the Indonesian coast, and its identity confirmed by comparison of its spectral data with that of synthetic material. Bisdemethylaaptamine-9- O -sulfate ( 7 ) was also isolated from the same source. This is the first report of a sulfated aaptamine.

A general procedure has been established for the synthesis of 11,13-dihydroxy gibberellins. The key steps involve the isomerization of the 19,10 lactone functionality to the 19,2-isomer, bromination at C-1 and C-11, then selective nucleophilic displacement of the 11-bromo substituent by acetate with silver(1) acetate. Reconstitution of the 19,10 lactone functionality was effected by bromolactonization of a ∆ 9 -ene 19-carboxylic acid to give a 9β-bromo 19,10-lactone followed by stereoselective hydrogenolysis of the bromo substituent.

Some gibberellin (GA) analogues, especially with C-16,17 modifications of GA(5), can inhibit growth of plants apparently by acting as competitors with the endogenous substrate of GA biosynthetic enzymes. Here, we directly confirm the competitive action of GA derivatives but also show that some analogues may retain significant bioactivity. A recombinant 3-oxidase from pea, which converts GA(20) to bioactive GA(1), was inhibited by GA(5), and 16,17-dihydro-GA(5) derivatives, especially if the C-17 alkyl chain length was increased by up to three carbons or if the C-13 hydroxyl was acetylated. Genetic confirmation that GA(5) analogues target 3-oxidases in vivo was provided by comparing the growth response of a WT (LE) pea with a 3-oxidase mutant (le-1). Two pea 2-oxidases that inactivate bioactive GAs, were inhibited by GA(1) and GA(3) but were generally insensitive to GA(5) analogues. alpha-Amylase production by barley half-seeds in response to GA analogues provided a method to study their action when effects on GA biosynthesis were excluded. This bioactivity assay showed that 16,17-dihydro GA(5) analogues have some inherent activity but mostly less than for GA(5) (5-50-fold), which in turn was 100-fold less active than GA(1) and GA(3). However, although C-17 alkyl derivatives with one or two added carbons showed little bioactivity and were purely 3-oxidase inhibitors, adding a third carbon (the 17-n-propyl-16,17-dihydro GA(5) analogue) restored bioactivity to that of GA(5). Furthermore, this analogue has lost its capacity to inhibit stem elongation of Lolium temulentum (Mander et al., Phytochemistry 49:1509-1515, 1998a), although it strongly inhibits the 3-oxidase. Thus, the effectiveness of a GA derivative as a growth retardant will reflect the balance between its bioactivity and its capacity to inhibit the terminal enzyme of GA biosynthesis. The weaker growth inhibition in dicots including pea (approximately 10%) than in monocots such as L. temulentum (>35%) is suggestive of taxonomic differences in the bioactivity of GAs and/or their effects on GA biosynthesis.

An improved five-step procedure has been developed for the synthesis of the gibberellin plant growth inhibitor 16,17-dihydro-GA5 from gibberellic acid. The 3-13C and 3-14C derivatives of this material have also been prepared by excising C-3 from the carbon skeleton (ozonolysis of a Δ2-alkene derivative and subsequent retro-Claisen reaction) and then reassembling the A-ring by means of an intramolecular aldol reaction.Key words: gibberellin, growth inhibitor, degradation, Radio labelling, Wittig reaction.

Petunia (Petunia X hybrida Vilm.) 'Baccarat Blue' under high pressure sodium lamp (HPS) exhibits, dwarfism compared with one grown under a daylight type metal halide lamp (MH). The role of gibberellin (GA) in this growth change, caused by artificial lighting was investigated. The amounts of GA20 and GA1 were lower in petunia grown under HPS than those under MH, but, the levels of GA19 were similar in both treatments. Plant height of petunia was decreased by treatment with uniconazol, but the difference in plant height between treatments was small. GA3 application promoted stem elongation of uniconazol-treated petunia; the magnitude of stem elongation was independent of light source. These results indicate that dwarfism in petunia under HPS is caused by lower GA20 and GA1 contents, but not by GA sensitivity. The GA biosynthesis step of GA19 to GA20 may be affected by the light quality of these lamps.

SummaryHeat-induced rosetted Eustoma grandiflorum requires low temperature for induction of stem elongation and flowering. Although heat-induced rosetting is associated with a reduction of gibberellin A1 (GA1) content, how thermo-induction affects GA biosynthesis is unclear. Thus, we examined levels of GA, precursors including that of ent-kaurene which is the first committed step in GA biosynthesis. We used uniconazole, an ent-kaurene oxidase inhibitor to estimate the ent-kaurene biosynthesis activity. The accumulation level of ent-kaurene in stems of the cold-treated seedlings was approximately 1.8 times that of the non-cold-treated seedlings, whereas no difference was observed in the leaves. No change was observed in endogenous levels of GA1 and GA20 in stems of the heat-induced rosetted plants during the cold treatment, whereas their levels increased with stem elongation after transfer to warm conditions. In contrast to the levels of GA1 and GA20, endogenous levels of ent-kaurene, ent-kaurenoic acid, G...

Norcaradiene derivatives derived from the copper-catalyzed intramolecular cyclopropanation reactions of 2-(5-vinyl-1,2,3,4-tetrahydronaphthalene) diazomethyl ketones have been prepared and submitted to Diels–Alder reactions with a range of dienophiles, including methyl acrylate, methyl 2-chloroacrylate, maleic anhydride and citraconic anhydride. The cycloaddition reactions gave better yields and were more selective when the vinyl norcaradienes were based on 8methoxynaphthyl diazoketones.

Charles Shoppee was a major figure in research into the steroid family of organic compounds. After an extensive grounding in mechanistic organic chemistry with such major figures as Sir Jocelyn Thorpe FRS at Imperial College and Sir Christopher Ingold FRS at the University of Leeds, Shoppee spent the war years in Basel working with Tadeus Reichstein (ForMemRS 1952). There he began to apply reaction mechanistic concepts to the reactions of natural products, particularly steroids, in which he was in the vanguard of a huge and widespread activity prompted, in part, by the pharmaceutical industry's interests in these important compounds. However, in additional to their therapeutic potential they provided a rigid template on which one could explore aspects of structure determination, synthesis, mechanism and stereochemistry. After the war, Shoppee spent a brief period in London before taking up the chair of chemistry at the University of Wales, Swansea, where he built up the research strengths of the Chemistry Department and continued to build a major opus on the synthesis, stereochemistry and physical-organic chemistry of steroids during the following eight years. These interests were continued for a further 13 years at the University of Sydney until his formal retirement in 1969. After a period of five years at Texas Technological University, he returned to Australia and maintained his commitment to science until the end, still working at the bench in his 87th year.

This review covers research into the chemistry and biology of the gibberellin family of plant bioregulators carried out in the author's laboratory over the past 20 years and has 231 references.

Extracts of stems of growing shoots of Populus deltoides and P. trichocarpa, and developing capsules of P. deltoides were analysed for gibberellins (GAs) by gas chromatography-mass spectrometry. The following known GAs were identified by comparison of their Kovats retention indices (KRIs) and mass spectra with those of standards: GA1, GA8, GA9, GA19, GA20, 16 beta,17-dihydro-17-hydroxy GA20, GA23, GA28, GA29, GA34, GA44, and GA97. Several of these have not been previously reported from Populus. In addition, two new GAs were identified as 12 beta-hydroxy GA53 (GA127) and 16 beta,17-dihydro-17-hydroxy GA53 and their structures were confirmed by partial synthesis. Evidence was found of 16,17-dihydro-16,17-dihydroxy GA9, 16,17-dihydro-16,17-dihydroxy GA12, 12-hydroxy GA14, and GA34-catabolite by comparison of mass spectra and KRIs with published data. Several putative GAs (hydroxy- and dihydroxy-GA12-like) were also found. The catabolites of active GAs or of key precursors, hydroxylated at C-2 in stems and either C-2, C-12, C-17, or C-16,17 in capsules, were the major proportion of the GAs.

The ability of exogenous gibberellin (GA) A3 to substitute for low temperatures in inducing flowering in Phalaenopsis hybrida under high temperatures suggests a similar role for endogenous GAs in normal (low temperature) development of the inflorescence and floral buds. Changes in endogenous GAs in shoot-tips (about 2.0 cm long) were examined when the potentially flowering shoot was 2–3 cm and 7–10 cm long, respectively. Treatments included warm control (30/25 °C day/night, non-flowering), GA3-treated (30/25 °C day/night, flowering) and cool-induced (25/20 °C day/night, flowering) plants. GA3 at 0.5 μg·shoot–1 was injected into the cavity of the second visible bud scale below the flowering shoot apex. The contents in the tips of potentially flowering shoots of GA1, GA20, GA19 and GA53 tended to be highest in cool-induced plants, intermediate in GA3-treated plants, and lowest in the warm controls (non-flowering). Tips of potentially flowering shoots in warm controls also contained higher GA8 relative to GA3-treated and cool-induced plants. Tips of potentially flowering shoots (2–3 cm in length with no flower primordium), contained low levels of GAs than older 7–10 cm long flowering shoots (with flower primordia) under cool-inductive conditions. These results suggest that continued inflorescence development and flower bud initiation are closely associated with increases in endogenous GAs, even in GA3-treated plants. They also suggest that a more rapid biosynthetic flow-through from GA19→GA20→GA1→GA8 leaving reduced levels of GA1 may be involved in the inhibition of flowering and shoot elongation seen in warm (30/25 °C day/night) control plants. A reduced conversion of ‘active’ GA1 to inactive GA8 may thus be required for successful floral induction and development whether induced by cool temperatures or by applied GA3. These results imply that the high temperature inhibitory effect on flowering is mediated through its effect on lowering the level of endogenous GA1 and its precursors.

Recently, it was found that stem elongation and flowering of stock Matthiola incana (L.) R. Br. are promoted by exogenous gibberellins (GAs), including GA4, and also by acylcyclohexanedione inhibitors of GA biosynthesis, such as prohexadione-calcium (PCa) and trinexapac-ethyl (TNE). Here, because it was unclear how GA biosynthetic inhibitors could promote stem elongation and flowering, their effect on GA biosynthesis has been examined by quantifying endogenous GA levels; also, the sensitivity of stem elongation and flowering to various GAs in combination with the inhibitors was examined. Stem elongation and flowering were most effectively promoted by GA4 when combined with PCa and, next in order, by 2,2-dimethyl-GA4, PCa, GA4+TNE, TNE, GA9+PCa and by GA4. There was little or no promotion by GA1, GA3, GA9, GA13, GA20 and 3-epi-2,2-dimethyl-GA4. Both the promotive effects of the acylcyclohexanediones on stem elongation and flowering, particularly when applied with GA4, and the fact that TNE caused a build-up of endogenous GA4 imply that one effect of TNE at the lower dose involved an inhibition of 2β-hydroxylation of GA4 rather than an inhibition of 20-oxidation and 3β-hydroxylation of GAs which were precursors of GA4. Overall, these results indicate that: (1) GAs with 3β-OH and without 13-OH groups (e.g. GA4) are the most important for stem elongation and flowering in M. incana; (2) growth promotion rather than inhibition can result if an acylcyclohexanedione acts predominantly to slow 2β-hydroxylation and so slows inactivation of active gibbberellins, including GA4. It follows that a low dose of an acylcyclohexanedione can be a ‘growth enhancer’ for any applied GA that is liable to inactivation by 2β-hydroxylation.

Extracts of acids from mature seeds, germinating seeds, first, second and third year seedlings as well as mature, flowering trees of sweet cherry (Prunus avium L. cv. Stella) were analysed by gas chromatography-mass spectrometry. The presence of the known gibberellins (GAs) GA1 (1), GA3 (4), GA5 (7), GA8 (11), GA19 (14), GA20 (12), GA29 (13), GA32 (5), GA85 (2), GA86 (3) and GA87 (6) was confirmed by comparison of their mass spectra and Kovats retention indices with those of standards or literature values. In addition, 16alpha,17-dihydrodihydroxy GA25 (16) was identified and its stereochemistry confirmed by rational synthesis. The 12alpha,13-dihydroxy GAs, GA32 (5), GA86 (2), GA86 (3) and GA87 (6), were detected in mature seeds, germinating seeds and young seedlings, but not in flowering plants. The 13-hydroxy GAs, GA1 (1) and GA3 (4), were present in germinating seeds and, in addition to these, GA5 (7), GA8 (11), GA19 (14), GA20 (12) and GA29 (13) were detected in seedlings and mature flowering plants. In germinating seeds and seedlings (while the plants were growing actively), concentrations of the 12alpha,13-dihydroxy GAs, measured by bioassay, declined and those of the 13-hydroxy GAs increased. The results are discussed with reference to the known and predicted effects of the GAs on the vegetative growth and flowering of P. avium plants.

Treatments with gibberellin A1(GA1), GA3 and GA20 promoted stem elongation in rosetted seedlings of Eustoma grandiflorum in the following order : GA1=GA3>GA20, whereas ent-kaurene (K), ent-kaurenoic acid (KA) and GA19 did not. GA1, GA3, GA19 and GA20 treatments promoted leaf elongation in the order of GA1=GA3=GA20 > GA19, although K and KA did not. Quantitative analysis of endogenous GAs suggested that GA-biosynthesis pathway prior to GA53 might be blocked in the rosetted plants. Furthermore, the results of stem and leaf elongation by the GA treatment indicate that there was a difference in 20-oxidase activity between stem and leaves of rosetted plants. Quantitative analyses also provided evidence that there were tissue-specific 20-oxidase activities not only in the rosetted plants but also in the non-rosetted plants of E. grandiflorum. GA3-induced stem elongation, but not floral initiation in rosetted plants under 35°/30°C. Uniconazole (UCZ) inhibited leaf expansion, stem elongation and flower bud development of the non-rosetted plants, but did not inhibit flower bud initiation. These results indicate that leaf expansion, stem elongation and flower bud development are apparently GA-dependent but flower bud initiation is not.

The modified gibberellins, 16-methyl-16,17-dihydro-GA 5 , 16,17-methano-16,17-dihydro-GA 5 , 16,17-methano-16,17-dihydro-GA 3 and several halogenated derivatives of 16,17-methano-16,17-dihydro-GA 3 and GA 5 were prepared and tested for bioregulating properties in Lolium temulentum . The effects ranged from the promotion of both stem elongation and flowering, the promotion of flowering but not elongation, and vice versa , the inhibition of stem elongation combined with the promotion of flowering, and the inhibition of both.

The structure of a new gibberellin-like antheridiogen from gametophytes of the fern Lygodium circinnatum has been confirmed as the methyl ester of 12α-hydroxy gibberellin A73 (GA117) by synthesis of an authentic sample from the 17-nor-16-one derived from GA73. Comparative bioassays of the synthetic compound as an antheridium inducing substance in Lygodium japonicum showed that it is highly potent, with activity in the picomolar range, and that it is considerably more active than the 12β-epimer (GA96).

A general protocol for the 14-hydroxylation of the gibberellin molecule has been developed and is illustrated by the conversion of gibberellic acid (GA3) into the methyl ester of 14β-hydroxy GA1. The key steps involved oxidative cleavage of the methylene group, hydrogenation and acyloin rearrangement of the resulting 13-hydroxy-17-nor-16-one to afford the 8α, 13α diastereomer. A hydroxy group was introduced adjacent to the 16-one function and then a further acyloin rearrangement effected, thereby restoring the normal gibberellin configuration with the extra hydroxyl located at C-14. Wittig methylenation under forcing conditions, followed by deprotection then afforded the target gibberellin. The sterically hindered methoxycarbonyl function group in this compound was unexpectedly partially transformed into an isopropenyl group.

The Diels Alder reactions of 5-methoxyindenone followed by intramolecular cyclopropanation provide the basis for a new and more efficient approach to the synthesis of the unusual diterpenoid tropone, harringtonolide.

Endogenous gibberellins of seeds and shoots of Raphanus sativus have been reanalyzed by GC-MS. Six 12-hydroxy C 20 -gibberellins (GA 111 (12α-hydroxy GA 12 ), GA 112 (12β-hydroxy GA 12 ), 12α-hydroxy GA 15 , 12β-hydroxy GA 15 , 12α-hydroxy GA 24 and 12β-hydroxy GA 24 ), and GA 5 , GA 40 , GA 95 -isolactone and 3- epi -GA 34 were identified as their methyl ester and TMSi ether derivatives. Of these gibberellins, 12α-hydroxy GA 15 , 12β-hydroxy GA 15 , 12α-hydroxy GA 24 and 12β-hydroxy GA 24 were allocated the descriptors GA 113 , GA 114 , GA 115 and GA 116 , respectively. In addition, GA 20 ethyl ester was identified as its TMSi ether derivative.

9,11-Didehydrogibberellin A 24 has been prepared from GA 3 and shown to be the biosynthetic precursor of the potent antheridiogen, gibberellin A 73 methyl ester, in prothallia of the ferns Lygodium flexuosum and Lygodium circinnatum .