Enantioselective total syntheses of indolizidine alkaloids (-)-205A and (-)-235B

Polniaszek, Richard P.; Belmont, Stephen E.

doi:10.1021/jo00016a013

Cited by 68 publications

(39 citation statements)

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“…Both epimers of hydrazone (R,R)-9 were then subjected to 1,2-addition by an organocerium reagent prepared from 3-tert-butyldimethylsiloxypropyllithium (6) and cerium(III) chloride at -100 ºC to furnish hydrazine 10 in 82% yield as a 95:5 mixture of the (R,R,S) and (R,S,S) epimers (de = 90%), while no other stereoisomer could be detected. Treatment of (R)-8 with LDA at 0 ºC resulted in the formation of the aza-enolate, which was alkylated at -100 ºC with 2-(2-iodoethyl)-1,3-dioxolane (7) 7 to yield hydrazone (R,R)-9 with high diastereomeric excess (de = 90%) in 81% yield.…”

Section: Methodsmentioning

confidence: 99%

“…3 The structural assignments of several indolizidine and quinolizidine alkaloids are still tentative, since they occur only in trace amounts in the frog skins too small for structure elucidation by NMR-spectroscopy. 6 They were able to prepare indolizidine 205A (4) and 235B (5) from a-amino nitrile precursor 3 by alkylation and subsequent stereoselective reduction with sodium borohydride (Scheme 1). 1 The relative configurations of both have been determined by GC analysis of a natural sample and comparison with racemic samples prepared by Rassat et al The tentative absolute configuration has been assigned in accordance with those of other dendrobatid 5,8-disubstituted indolizidine alkaloids of known configuration.…”

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confidence: 99%

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First Enantioselective Synthesis of Dendrobatid Alkaloids Indolizidine (-)-209I and (-)-223J

2000

Synlett

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The first asymmetric synthesis of dendrobatid indolizidine alkaloids (-)-209I [(5R,8R,8aS)-1a] and (-)-223J [(5R,8R,8aS)-1b] via a common late-stage intermediate amino nitrile (5R,8R,8aS)-2 are described. Amino nitrile 2 was synthesized employing the highly diastereoselective 1,2-addition of an organocerium reagent to a-substituted aldehyde RAMP-hydrazone (R,R)-9, which was in turn prepared in two steps starting from n-pentanal. The hydrazine obtained in this way was converted to pyrrolidine (R,S)-13, from which amino nitrile (5R,8R,8aS)-2 was obtained. Indolizidines (-)-209I and (-)-223J (de = 96 -99%, ee > 99%) and their C-5 epimers (5S,8R,8aS)-1a, b were prepared from 2 by alkylation/stereoselective reduction and stereoselective Bruylants reaction, respectively.

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Section: Methodsmentioning

confidence: 99%

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confidence: 99%

First Enantioselective Synthesis of Dendrobatid Alkaloids Indolizidine (-)-209I and (-)-223J

2000

Synlett

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“…Products of types 2 and 3 have considerable interest as valuable intermediates for the total synthesis of pyrrolizidine alkaloids, such as pseudoheliotridane, 6 isoretronecanol, 7 and platynecine, 8 as well as some biologically active products (e.g., highly selective EP4 antagonists 9 ). Furthermore, many heterocycles of types 2 and 3 possess their own high biological activity.…”

Section: Figurementioning

confidence: 99%

“…1 3.89 (ddd, J = 9.9, 7.3, 7.0 Hz, 1 H, H2), 6.86 (d, J = 8. 6 Hz, 2 H, H11), 7.13 (d, J = 8. 6 Hz, 2 H, H10).…”

Section: Rel-(5s)-5-{(s)-[(1r2r)-2-hydroxycyclohexyl](4-methoxyphenymentioning

confidence: 99%

Synthesis of Substituted 5-(3-Hydroxypropyl)pyrrolidin-2-ones and Pyrrolizidinones from Nitroethane via C3 Functionalized 5,6-Dihydro-4H-1,2-oxazines: A Novel Approach to Some Analogues of the Antidepressant Rolipram

Sukhorukov¹,

Lesiv²,

Khomutova³

et al. 2009

Synthesis

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D i a s t e r e o s e l e c t i v e S y n t h e s i s o f S u b s t i t u t e d a -P y r r o l i d o n e D e r i v a t i v e s f r o m N i t r o e t h a n eAbstract: Easily accessible [(5,6-dihydro-4H-1,2-oxazin-3-yl)methyl]malonates 1 were converted into substituted 5-(3-hydroxypropyl)pyrrolidin-2-ones 2 and pyrrolizidinones 3, which are versatile products and intermediates for organic and bioorganic chemistry. The synthetic sequence suggested includes stereoselective two-step reduction of an oximino fragment, followed by intramolecular cyclization involving one of the CO 2 Me groups and decarboxylation in the last stage. The efficiency of this strategy was demonstrated by the stereoselective synthesis of pyrrolizidinone rac-4, a highly efficient analogue of antidepressant Rolipram, from nitroethane.

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“…14 The angular nitrogen atom could, in turn, arise from a Curtius-type rearrangement, thus leading back to carboxylic acid 7 . This disconnection then prompted the possibility of using the ester precursor of the acid as a dienophilic activating group to build the CDE ring system of the molecule via a Diels-Alder reaction between 9 and 10 , with facial selectivity guided by the distal stereocenter in indolizidine 10 .…”

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confidence: 99%

Total Synthesis of Aspeverin via an Iodine(III)-Mediated Oxidative Cyclization

Levinson

2014

Org. Lett.

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The first total synthesis of aspeverin, a prenylated indole alkaloid isolated from Aspergillus versicolor in 2013, is described. Key steps utilized to assemble the core structure of the target include a highly diastereoselective Diels-Alder reaction, a Curtius rearrangement, and a unique strategy for installation of the geminal dimethyl group. A novel iodine(III)-initiated cyclization was then used to install the bicyclic urethane linkage distinctive to the natural product.

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Enantioselective total syntheses of indolizidine alkaloids (-)-205A and (-)-235B

Cited by 68 publications

References 0 publications

First Enantioselective Synthesis of Dendrobatid Alkaloids Indolizidine (-)-209I and (-)-223J

First Enantioselective Synthesis of Dendrobatid Alkaloids Indolizidine (-)-209I and (-)-223J

Synthesis of Substituted 5-(3-Hydroxypropyl)pyrrolidin-2-ones and Pyrrolizidinones from Nitroethane via C3 Functionalized 5,6-Dihydro-4H-1,2-oxazines: A Novel Approach to Some Analogues of the Antidepressant Rolipram

Total Synthesis of Aspeverin via an Iodine(III)-Mediated Oxidative Cyclization

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