Synthèse des 1-amidopyrrolizidines naturelles, absouline et laburnamine, de dérivés et d'analogues pyrrolidinoimidazoliques

Christine, Caline; Ikhiri, Khalid; Ahond, A.; Al‐Mourabit, Ali; Poupat, C.; Potìer, Pierre

doi:10.1016/s0040-4020(00)00088-0

Cited by 22 publications

(17 citation statements)

References 27 publications

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“…3) by reducing (±)-1-oximinopyrrolizidine with Raney nickel in tetrahydrofuran (THF) until starting material had been consumed. At this point, we observed one major and one minor spot by TLC, consistent with the formation of diastereomers (±)- 1a and (±)- 1b , respectively, as previously reported for the reduction of the oxime in isopropanol (Christine et al, 2000; Faulkner et al, 2006). We then added Ac 2 O and 4-dimethylaminopyridine (DMAP) to the reaction mixture.…”

Section: Resultssupporting

confidence: 91%

Ether bridge formation in loline alkaloid biosynthesis

et al. 2014

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Lolines are potent insecticidal agents produced by endophytic fungi of cool-season grasses. These alkaloids are composed of a pyrrolizidine ring system and an uncommon ether bridge linking carbons 2 and 7. Previous results indicated that 1-aminopyrrolizidine was a pathway intermediate. We used RNA interference to knock down expression of lolO, resulting in the accumulation of a novel alkaloid identified as exo-1-acetamidopyrrolizidine based on high-resolution MS and NMR. Genomes of endophytes differing in alkaloid profiles were sequenced, revealing that those with mutated lolO accumulated exo-1-acetamidopyrrolizidine but no lolines. Heterologous expression of wild-type lolO complemented a lolO mutant, resulting in the production of N-acetylnorloline. These results indicated that the non-heme iron oxygenase, LolO, is required for ether bridge formation, probably through oxidation of exo-1-acetamidopyrrolizidine.

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Section: Resultssupporting

confidence: 91%

Ether bridge formation in loline alkaloid biosynthesis

et al. 2014

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“…The colorless gummy mass thus obtained was purified by flash chromatography (33 % EtOAc in petroleum ether) to obtain 7 (1.15 g, 4.15 mmol, 80 % yield) as a colorless gum. (S)-N-tert-Butoxycarbonyl-4-deuteroaspartic acid 4-semialdehyde tertbutyl ester (8): A solution of the protected 4,4-dideuterohomoserine 7 (1.10 g, 4.00 mmol) in CH 2 Cl 2 (5 mL) was added slowly to a solution of Dess-Martin periodinane (2.00 g, 4.70 mmol) in CH 2 Cl 2 (10 mL) at 0 8C under N 2 , and the mixture was stirred at RT for 1.5 h. The reaction mixture was then diluted with ether (100 mL) and filtered through Celite. The filtrate was washed with saturated aqueous sodium thiosulfate (50 mL) and brine (50 mL), dried over MgSO 4 , and evaporated.…”

Section: Methodsmentioning

confidence: 99%

“…[8] Ketone 20 was also prepared by N-alkylation of ethyl prolinate with ethyl acrylate, followed by Dieckmann cyclization, hydrolysis, and decarboxylation. [10] Two asymmetric syntheses of 6 that did not proceed through 20 were also reported, but both were precluded for our purposes by length, poor diastereoselectivity, and low overall yield.…”

Section: Introductionmentioning

confidence: 99%

“…[11,12] We decided to combine aspects of the previously reported procedures to prepare 20 and then 6 (Scheme 5). [8][9][10] Ethyl prolinate [13] was combined with neat ethyl acrylate to give amine 21 in good yield. [10,14] The amine 21 was subjected to Dieckmann cyclization, hydrolysis, and decarboxylation to give 20.…”

Section: Introductionmentioning

confidence: 99%

“…Oxime 22 was then subjected to Raney Ni reduction to give 34 % 6 and 5 % 1-epi-6. [8] (Note on attempting to prepare 6: its NMR spectra are highly concentration-dependent, and this can confound one's efforts to determine whether one has actually obtained the compound. NMR spectra of compounds 6, 6 a, and 6 b at different concentrations are provided in the Supporting Information.)…”

Section: Introductionmentioning

confidence: 99%

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On the Sequence of Bond Formation in Loline Alkaloid Biosynthesis

et al. 2006

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Loline alkaloids are saturated pyrrolizidines with an oxygen bridge between carbon atoms C-2 and C-7 and an amino group on C-1. They are bioprotective alkaloids produced by Epichloë and Neotyphodium species, mutualistic fungal endophytes that are symbiotic with cool-season grasses. The sequence of bond formation in loline alkaloid biosynthesis was determined by synthesizing deuterated forms of potential intermediates and feeding them to cultures of the endophyte Neotyphodium uncinatum. These cultures incorporated deuterium from labeled N-(3-amino-3-carboxypropyl)proline and exo-1-aminopyrrolizidine into N-formylloline. The first result suggests that N-(3-amino-3-carboxypropyl)proline is the first committed intermediate in loline biosynthesis, and the second result demonstrates that the pyrrolizidine rings form before the ether bridge. The incorporation of these two compounds into lolines and the lack of incorporation of several related compounds clarify the order of bond formation in loline alkaloid biosynthesis.

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Synthesis of Diamino Carboxylic Esters by Palladium‐Catalyzed Oxidative Intramolecular Diamination of Acrylates

Muñiz

Streuff

Chávez

et al. 2008

Chemistry An Asian Journal

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Unligated palladium(II) salts catalyze the oxidative diamination of acrylic esters to yield 2,3-diamino carboxylic esters. The reaction employs copper(II) bromide as oxidant and proceeds with good to excellent stereoselectivities and complete chemoselectivity. Preliminary mechanistic studies provide evidence for the involvement of a direct amination of the C--Pd bond in the alpha position relative to the ester group. This protocol significantly broadens the overall scope of the palladium-catalyzed diamination of alkenes and represents the first direct diamination of functionalized nonterminal substrates. The reaction yields readily protected 2,3-diamino acid derivatives, which can be considered as highly functionalized building blocks for subsequent synthesis. The use of one of these new diamination products as a suitable starting material in a short synthesis of the alkaloid absouline is demonstrated as an example.

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Synthèse des 1-amidopyrrolizidines naturelles, absouline et laburnamine, de dérivés et d'analogues pyrrolidinoimidazoliques

Cited by 22 publications

References 27 publications

Ether bridge formation in loline alkaloid biosynthesis

Ether bridge formation in loline alkaloid biosynthesis

On the Sequence of Bond Formation in Loline Alkaloid Biosynthesis

Synthesis of Diamino Carboxylic Esters by Palladium‐Catalyzed Oxidative Intramolecular Diamination of Acrylates

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