Rapid chromatographic technique for preparative separations with moderate resolution

Still, W. Clark; Kahn, Michaël; Mitra, Abhijit

doi:10.1021/jo00408a041

Cited by 6,277 publications

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“…The mixture was then extracted with t-BuOMe, with the organic layer dried over anhydrous Na 2SO4 and the solvent removed. Flash chromatography 21 (hexane/t-BuOMe 13 C NMR spectra matched those reported elsewhere. 17,22 Incubation Procedure.…”

Section: Methodssupporting

confidence: 69%

Microbial Transformation of ent-Kaurenoic Acid and Its 15-Hydroxy Derivatives by the SG138 Mutant of Gibberella fujikuroi

et al. 2001

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Feeding experiments with ent-kaurenoic acid (4), 15R-hydroxy-ent-kaurenoic acid (5), 15 -hydroxy-entkaurenoic acid (6), and mixtures of 4 plus 5 and 4 plus 6 were conducted using the SG138 mutant of Gibberella fujikuroi, to gain information about the phenotype of this unique strain. The biotransformation of 5 gave 7 ,15R-dihydroxykaurenolide (9) and 7 ,15R-dihydroxy-ent-kaurenoic acid (13). The incubation of 6 produced 7 ,15 -dihydroxy-ent-kaurenoic acid (7) and 7 ,15 -dihydroxykaurenolide (10). No 15-hydroxylated gibberellins were detected in any of these experiments. The results indicated that a hydroxy group at C-15 does not inhibit 7 -hydroxylase activity but in the SG138 strain obstructs the enzymatic ring-B contraction of ent-kaurenoids to gibberellins. Exogenous 4 stimulated both the excretion of ent-kaurene and the fungal metabolism of 5 and 6. Gibberellins (GAs) are terpenoid phytohormones which play an important role in the regulation of plant growth and development. Apart from plants some fungi also produce these terpenoids, particularly Gibberella fujikuroi (Hypocreale). GAs have many applications in agriculture and the brewing industry. 1 Therefore, their abundant production by some strains of G. fujikuroi has led to the study of their biosynthesis by this fungus in considerable detail over the last three decades. 2 Some aspects of the biogenesis of the gibberellins via ent-kaurene (1), entkaurenol (2), ent-kaurenal (3), and ent-kaurenoic acid (4) are fully described, 2 but many of the biochemical and physiological aspects of fungal gibberellin biosynthesis are still poorly understood. As part of our research into the biotechnology of G. fujikuroi we have investigated the metabolites produced by the GA-producer IMI58289 strain. 3,4 Subsequently, the kaurenoids and GAs synthesized by several gib-mutants developed from the IMI58289 wildtype strain were also analyzed. 5 The results of these analyses and preliminary feeding experiments 6 suggested to us that one of these mutants (SG138) was blocked in the oxidative transformations from ent-kaurene (1) to entkaurenoic acid (4), as well as in 3 -hydroxylation, 13 -hydroxylation, and the loss of C-20 by the GAs. These unusual features prompted us to make further feeding experiments with strain SG138 to gain more information about its unusual phenotype. We describe here the results of incubations with ent-kaurenoic acid (4), the "unnatural" substrates 15R-hydroxy-ent-kaurenoic acid (5) and 15 -hydroxy-ent-kaurenoic acid (6), and mixtures of 4 plus 5 and 4 plus 6. Throughout these experiments it was observed that ent-kaurenoic acid (4) substantially stimulated the metabolism and/or excretion of 1, 5, and 6.The results of incubations using the SG138 mutant of G. fujikuroi, both with and without ent-kaurenoic acid (4), are summarized in Table 1. All compounds included in this table were identified by means of GC-MS. Several substances could be isolated, and their structures were confirmed by NMR techniques (see the Experimental Section for more details). A num...

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Section: Methodssupporting

confidence: 69%

Microbial Transformation of ent-Kaurenoic Acid and Its 15-Hydroxy Derivatives by the SG138 Mutant of Gibberella fujikuroi

et al. 2001

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“…Visualization was achieved by UV illumination. Flash chromatography was performed according to Still et al [15] using Aldrich silica gel (70-230 mesh). All chemicals were purchased from Aldrich Chemicals and used without further purification.…”

Section: General Considerations and Materialsmentioning

confidence: 99%

An unexpected ‘4+2’ [N3S]/[NS] rhenium(IV) complex formed upon cleavage of a Re(V) imido bond

Chen

Femia

Babich³

et al. 2000

Inorganica Chimica Acta

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“…All moisture-and airsensitive reactions were conducted under argon. Column chromatography refers to flash chromatography using Silica Gel 60 (230-400 mesh, E Merck, Darmstadt, Germany) (Still et al, 1978). Thin-layer chromatography (TLC) was conducted on aluminum-backed plates precoated with Merck Silica Gel 60F-254 as the adsorbent, and visualized by treatment with an acidic solution of 1% Ce(S04h and 1.5 % molybdic acid followed by gentle heating.…”

Section: Instruments and General Synthetic Proceduresmentioning

confidence: 99%

Aggregation pheromone of coconut rhinoceros beetle,Oryctes rhinoceros (L.) (coleoptera: Scarabaeidae)

et al. 1995

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Abstract-Male coconut rhinoceros beetles, Orycres rhinoceros (L.), produce three sex-specific compounds, ethyl 4-methyloctanoate, ethyl 4-methylheptanoate, and 4-methyloctanoic acid, the first of which is an aggregation pheromone. Synthesis of these compounds involving conjugate addition of organocuprates to ethyl acrylate is reported. In field trapping experiments, (4S)-ethyl 4-methyloctanoate and the racemic mixture were equally attractive and 10 times more effective in attracting beetles than ethyl chrysanthemumate, a previously recommended attractant. Ethyl 4-methylheptanoate was as attractive as ethyl chrysanthemumate and more attractive than 4-methyloctanoic acid, but further studies are required before it can be classed as an aggregation pherornone. Compared to ethyl 4-methyloctanoate alone, combinations of the three male-produced compounds did not increase attraction, whereas addition of freshly rotting oil palm fruit bunches to pheromone-baited traps sjgnificantly enhanced attraction. With increasing dose, captures of O. rhinocerós'increased, but doses of 6, 9, and 18 mg/day were competitive with 30 mg/day lures. Newly designed vane traps were more effective in capturing beetles than were barrier or pitfall traps. Results of this study indicate that there is potential for using ethyl 4-methyloctanoate in operational programs to control O. rhinoceros in oil palm plantations.

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Rapid chromatographic technique for preparative separations with moderate resolution

Cited by 6,277 publications

References 0 publications

Microbial Transformation of ent-Kaurenoic Acid and Its 15-Hydroxy Derivatives by the SG138 Mutant of Gibberella fujikuroi

Microbial Transformation of ent-Kaurenoic Acid and Its 15-Hydroxy Derivatives by the SG138 Mutant of Gibberella fujikuroi

An unexpected ‘4+2’ [N3S]/[NS] rhenium(IV) complex formed upon cleavage of a Re(V) imido bond

Aggregation pheromone of coconut rhinoceros beetle,Oryctes rhinoceros (L.) (coleoptera: Scarabaeidae)

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