Copper(II) Chloride Mediated Racemization-Free Hydrolysis of α-Alkylated Ketone Samp-Hydrazones

Enders, Dieter; Hundertmark, Thomas; Łaźny, Ryszard

doi:10.1080/00397919908085731

Cited by 23 publications

(10 citation statements)

References 15 publications

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“…The formation of ketone (S)-6 was attained by hydrolytic cleavage using copper(II) chloride. 12 The product was isolated in 59% yield and an enantiomeric excess greater than 93%, attributed to partial racemisation during cleav- age. This ketone was also an intermediate in the synthesis of racemic 1 by Plaga et al 5 In this work, rac-6 was converted to the Markovnikov alcohol by treatment with trifluoroacetic acid followed by alkaline workup, which is not compatible with our asymmetric synthesis.…”

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confidence: 98%

First Asymmetric Synthesis of Stigmolone: The Fruiting Body Inducing Pheromone of the Myxobacterium Stigmatella Aurantiaca

Enders¹,

Ridder²

2000

Synthesis

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The asymmetric synthesis of (S)-and (R)-stigmolone [(S)-and (R)-1], an aggregation pheromone of the myxobacterium Stigmatella aurantiaca, starting from 4-methylpentan-2-one is described. The stereogenic centre at the C-5 position of the pheromone was generated via the SAMP/RAMP hydrazone method with high enantiomeric purity. It could be shown again that both enantiomers induce the fruiting body formation of the myxobacterium at concentrations of 1.0-30.0 nM.Myxobacteria like Stigmatella aurantiaca are Gram-negative, sticklike soil bacteria, which live in swarms on insoluble polymer surfaces like rotten wood. Gliding in a swarm has an immense profit for the food intake. This is due to an increase in the local density of secreted hydrolytic enzymes and therefore the amount of available soluble nutrients. The swarm and also the secreted slime serves as a carpet which prevents the loss of enzymes and nutrients. Typically for myxobacteria, S. aurantiaca exists in two different life cycles. In the vegetative growth cycle the population rises like normal bacteria through cell division, but under conditions of starvation the bacteria form multicellular fruiting bodies. 1, 2 These fruiting bodies have a treelike structure and contain the myxospores, which are dormant cells. The change from the vegetative growth to the so-called development cycle is induced by the aggregation pheromone 8-hydroxy-2,5,8-trimethylnonan-4-one, which is named stigmolone after its biological origin and structure according to Plaga et al. Furthermore, this group published the first isolation 3, 4 as well as a synthesis 5 of the racemate of this pheromone.The natural product was isolated in racemic form perhaps due to the extensive isolation and purification procedures and the sensitivity of a-substituted ketones to racemisation. Plaga et al. also discovered an active concentration of 1.0 nM for the fruiting body formation, which makes this pheromone one of the most effective, non-peptidic bacterial pheromones known. 4 Mori et al. reported an 'exchiral-pool' synthesis starting either with (R)-or (S)-citronellol shortly after the first publication of stigmolone. 6, 7 The bioassay of the enantiomers showed the same active concentration for the fruiting body formation as for the racemate and therefore the natural product seemed to be an enantiomeric mixture. 8 For further biological tests Mori et al. developed a new and short synthesis of the racemic pheromone. 9 We now want to present the first asymmetric synthesis of (S)-and (R)-stigmolone [(S)-and (R)-1] and describe the results for the bioassays, which were carried out by Plaga.The target molecule contains one stereogenic centre resulting from the methyl branching at the C-5 position a to the carbonyl group. Therefore, the RAMP/SAMP hydrazone method 10 was chosen to generate both enantiomers of the pheromone based on either enantiomer of the chiral auxiliary. As shown in the Scheme, 4-methylpentan-2-one (2) was treated with (R)-1-amino-2-(methoxymethyl)pyrrolidine (RAMP), both commercially availa...

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confidence: 98%

First Asymmetric Synthesis of Stigmolone: The Fruiting Body Inducing Pheromone of the Myxobacterium Stigmatella Aurantiaca

Enders¹,

Ridder²

2000

Synthesis

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“…Therefore, the hydrazones 3a؊e are precursors of versatile bifunctional, diastereo-and enantiomerically pure building blocks in synthesis. The ketone hydrazones 3f؊i were cleaved with a 1  aqueous solution of copper(II) chloride [15] to remove the chiral auxiliary and to regenerate the parent ketone functionality. The N-tosyl-protected γ-amino ketones 6f؊i were obtained in good to excellent yields (80Ϫ97%) and excellent enantiomeric excesses (ee Ն 98%) (6i: de, ee Ն 98%) (Scheme 4 and Table 3).…”

Section: Resultsmentioning

confidence: 99%

Asymmetric β-Aminoethylation of Ketones and Nitriles with Tosylaziridines Employing the SAMP-Hydrazone Method

2000

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The nucleophilic ring-opening of tosylaziridines with chiral aza-enolates is reported. The SAMP-/ RAMP-hydrazones 1a−h derived from aldehydes or ketones were reacted with tosylaziridine 2a to give the β-aminoethylated hydrazones 3a−h with good diastereoselectivity. Removal of the chiral auxiliary resulted in the formation of the γ-amino nitriles 4a−e or γ-amino ketones 6f−h in good yields and excellent enantiomeric excesses (ee Ն 98%). Ring-opening of the enantiopure, benzyl-substituted tosylaziridine 2b with aza-en-

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“…Deprotonierung von ( S )‐ 37 mit tert ‐Butyllithium und Abfangen des so erhaltenen Lithium‐Azaenolats mit verschiedenen Elektrophilen ergab die α‐alkylierten Hydrazone 39 mit ausgezeichneter Diastereoselektivität (88 bis ≥96 % de ). Das Auxiliar wurde anschließend racemisierungsfrei abgespalten – entweder oxidativ mit Ozon bei tiefer Temperatur oder in Zweiphasensystemen (wässrige Kupfer( II )chlorid‐39a oder Oxalsäure‐Lösungen39b zusammen mit einem organischen Cosolvens, z. B.…”

Section: Von Dha Abgeleitete Bausteine Und Ihre Verwendung In Der unclassified

Clonal Isolation of an Intermediate Pluripotent Stem Cell State

Chang

2013

Stem Cells

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Dihydroxyacetonphosphat (DHAP) dient der Natur als Methylenkomponente in verschiedensten enzymkatalysierten Aldolreaktionen. Das wohl wichtigste Beispiel in diesem Zusammenhang ist die Photosynthese, bei der d‐Glucose, der mengenmäßig bedeutendste Naturstoff, ausgehend von DHAP in nur wenigen Stufen gebildet wird. In den vergangenen Jahren wurde eine Vielzahl von synthetischen DHAP‐Äquivalenten entwickelt, die insofern besondere Aufmerksamkeit verdienen, als ihre Anwendbarkeit nicht auf (stereoselektive) Aldolreaktionen beschränkt ist. Die Reagentien stellten ihr Potenzial auch bei einer Reihe weiterer asymmetrischer elektrophiler α‐Substitutionen in zahlreichen zielgerichteten Synthesen überzeugend unter Beweis. Die verwandten 1,3‐Dioxine sind darüber hinaus nützliche Äquivalente 2‐substituierter Acroleine.

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Copper(II) Chloride Mediated Racemization-Free Hydrolysis of α-Alkylated Ketone Samp-Hydrazones

Cited by 23 publications

References 15 publications

First Asymmetric Synthesis of Stigmolone: The Fruiting Body Inducing Pheromone of the Myxobacterium Stigmatella Aurantiaca

First Asymmetric Synthesis of Stigmolone: The Fruiting Body Inducing Pheromone of the Myxobacterium Stigmatella Aurantiaca

Asymmetric β-Aminoethylation of Ketones and Nitriles with Tosylaziridines Employing the SAMP-Hydrazone Method

Clonal Isolation of an Intermediate Pluripotent Stem Cell State

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