- Synthesis of natural products from the Indian neem tree Azadirachta indica
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The synthesis of five natural products (3, 6, 7, 10, and 14), isolated from the Indian neem tree Azadirachta indica, is reported from a common intermediate (2). The judicious choice of transacetalization conditions allows efficient access to both the azadirachtinin (9 and 10) and the azadirachtin (3, 6, 7, and 14) skeletons
- Veitch, Gemma E.,Pinto, Andrea,Boyer, Alistair,Beckmann, Edith,Anderson, James C.,Ley, Steven V.
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p. 569 - 572
(2008/04/12)
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- The synthesis of azadirachtin: A potent insect antifeedant
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We describe in full the first synthesis of the potent insect antifeedant azadirachtin through a highly convergent approach. An O-alkylation reaction is used to unite decalin ketone and propargylic mesylate fragments, after which a Claisen rearrangement constructs the central C8-C14 bond in a stereoselective fashion. The allene which results from this sequence then enables a second critical carboncarbon bond forming event whereby the [3.2.1] bicyclic system, present in the natural product, is generated via a 5-exo-radical cyclisation process. Finally, using knowledge gained through our early studies into the reactivity of the natural product, a series of carefully designed steps completes the synthesis of this challenging molecule.
- Ley, Steven V.,Abad-Somovilla, Antonio,Anderson, James C.,Ayats, Carles,Baenteli, Rolf,Beckmann, Edith,Boyer, Alistair,Brasca, Maria G.,Brice, Abigail,Broughton, Howard B.,Burke, Brenda J.,Cleator, Ed,Craig, Donald,Denholm, Alastair A.,Denton, Ross M.,Durand-Reville, Thomas,Gobbi, Luca B.,Goebel, Michael,Gray, Brian Lawrence,Grossmann, Robert B.,Gutteridge, Claire E.,Hahn, Norbert,Harding, Sarah L.,Jennens, David C.,Jennens, Lynn,Lovell, Peter J.,Lovell, Helen J.,De La Puente, Mary L.,Kolb, Hartmuth C.,Koot, Win-Jan,Maslen, Sarah L.,McCusker, Catherine F.,Mattes, Amos,Pape, Andrew R.,Pinto, Andrea,Santafianos, Dinos,Scott, James S.,Smith, Stephen C.,Somers, Andrew Q.,Spilling, Christopher D.,Stelzer, Frank,Toogood, Peter L.,Turner, Richard M.,Veitch, Gemma E.,Wood, Anthony,Zumbrunn, Cornelia
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experimental part
p. 10683 - 10704
(2009/12/31)
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- A relay route for the synthesis of azadirachtin
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(Chemical Equation Presented) 22 Years in the making: Azadirachtin (1) was synthesized for the first time by a highly convergent approach, utilizing a Claisen rearrangement and a radical cyclization as key steps. End-game strategies relied on intermediate 2, which could be obtained by synthetic methods as well as by degradation of 1. Bn = benzyl, TBS = tert- butyldimethylsilyl.
- Veitch, Gemma E.,Beckmann, Edith,Burke, Brenda J.,Boyer, Alistair,Ayats, Carles,Ley, Steven V.
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p. 7633 - 7635
(2008/09/19)
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- Stable extracts from neem seeds
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A neem seed extract containing azadirachtin with improved stability has been developed using a process involving dissolution of the crude neem seed extract in a polar solvent and removal of impurities by precipitation and/or treatment of the extract with an oxidizing agent. The resulting extract, optionally formulated as a wettable powder, is a useful insecticide for the control of foliar pests.
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- Chemistry of Insect Antifeedants from Azadirachta Indica (Part 19): A Potential Relay Route for the Synthesis of Azadirachtin.
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A potential relay route for the synthesis of azadirachtin (1) has been established.An advanced intermediate 4 has been prepared and methods to convert this back to the natural product has been developed, in particular, the reintroduction of the enol double bond using an acetal exchange process.
- Denholm, Alastair A.,Jennens, Lyn,Ley, Steven V.,Wood, Anthony
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p. 6591 - 6604
(2007/10/02)
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- CHEMISTRY OF INSECT ANTIFEEDANTS FROM AZADIRACHTA INDICA (PART 11) : CHARACTERISATION AND STRUCTURE ACTIVITY RELATIONSHIPS OF SOME NOVEL REARRANGED AZADIRACHTINS.
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Several novel rearrangement reactions of the natural product azadirachtin and related derivatives have been characterised using a combination of x-ray crystallographic and high field nmr techniques.The insect antifeedant properties of these and a number of C7 modified compounds have been investigated.
- Ley, Steven V.,Anderson, James C.,Blaney, Wally M.,Morgan, E. David,Sheppard, Richard N.,et al.
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p. 9231 - 9246
(2007/10/02)
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- CHEMISTRY OF INSECT ANTIFEEDANTS FROM AZADIRACHTA INDICA (Part 3) REACTIONS ON THE C-22,23 ENOL ETHER DOUBLE BOND OF AZADIRACHTIN AND CONVERSION TO 22,23-DIHYDRO-23-&β-METHOXYAZADIRACHTIN.
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Azadirachtin (1) can be converted to the natural product 22,23-dihydro-23β-methoxyazadirachtin (2) via selective bromomethoxylation of the C-22,23 enol ether double bond and tri-n-butyltin hydride reduction; the corresponding acetic acid adduct on pyrolysis affords (1) in high yield.The antifeedant effects of the addition compounds were assessed.
- Ley, Steven V.,Anderson, James C.,Blaney, Wally M.,Lidert, Zev,Morgan, E. David,et al.
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p. 5433 - 5436
(2007/10/02)
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