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.
The synthesis of Azadirachtin: a potent insect antifeedant / S.V. Ley, A. Abad Somovilla, J.C. Anderson, C. Ayats, R. Banteli, E. Beckmann, A. Boyer, M.G. Brasca, A. Brice, H.B. Broughton, B.J. Burke, E. Cleator, D. Craig, A.A. Denholm, R.M. Denton, T. Durand Reville, L.B. Gobbi, M. Gobel, B.L. Gray, R.B. Grossmann, C.E. Gutteridge, N. Hahn, S.L. Harding, D.C. Jennens, L. Jennens, P.J. Lovell, H.J. Lovell, M.L. de la Puente, H.C. Kolb, W. Koot, S.L. Maslen, C.F. McCusker, A. Mattes, A.R. Pape, A. Pinto, D. Santafianos, J.S. Scott, S.C. Smith, A.Q. Somers, C.D. Spilling, F. Stelzer, P.L. Toogood, R.M. Turner, G.E. Veitch, A. Wood, C. Zumbrunn. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - 14:34(2008), pp. 10683-10704. [10.1002/chem.200801103]
The synthesis of Azadirachtin: a potent insect antifeedant
A. Pinto;
2008
Abstract
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.
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