- Steven Ley, University of Cambridge, UK, 1 G E Veitch et al, Angewandte Chemie, 2007, DOIs: 10.1002/anie.200703027 and 10.1002/anie.200703028
2 M L Maddess et al, Angewandte Chemie, 2006, 46, 591 (DOI: 10.1002/anie.200604053)
It was initially found to be active as a feeding inhibitor towards the desert locust(Schistocerca gregaria), it is now known to affect over 200 species of insect, by acting mainly as an antifeedant and growth disruptor, and as such it possesses considerable toxicity toward insects (LD50(S. littoralis): 15 μg/g). It fulfills many of the criteria needed for a natural insecticide if it is to replace synthetic compounds. Azadirachtin is biodegradable (it degrades within 100 hours when exposed to light and water) and shows very low toxicity to mammals(the LD50 in rats is > 3,540 mg/kg making it practically non-toxic).
Azadirachtin is formed via an elaborate biosynthetic pathway, but is believed that the steroid tirucallol is the precursor to the neem triterpenoid secondary metabolites. Tirucallol is formed from two units of farnesyl diphosphate (FPP) to form a C30 triterpene, but then loses three methyl groups to become a C27steroid. Tirucallol undergoes an allylic isomerization to form butyrospermol, which is then oxidized. The oxidized butyrospermol subsequently rearranges via a Wagner-Meerwein 1,2-methyl shift to form apotirucallol.
Azadirachtin ball and stick view
- Veitch GE, Beckmann E, Burke BJ, Boyer A, Maslen SL, Ley SV (2007). "Synthesis of azadirachtin: a long but successful journey". Angew. Chem. Int. Ed. Engl. 46 (40): 7629–32.doi:10.1002/anie.200703027. PMID 17665403.
- Sanderson K (August 2007). "Chemists synthesize a natural-born killer". Nature 448 (7154): 630–1. doi:10.1038/448630a.PMID 17687288.
- Butterworth, J; Morgan, E (1968). "Isolation of a Substance that suppresses Feeding in Locusts". Chemical Communications (London) (1): 23.doi:10.1039/C19680000023.
- Senthil-Nathan, S., Kalaivani, K., Murugan, K., Chung, G. (2005). "The toxicity and physiological effect of neem limonoids on Cnaphalocrocis medinalis (Guenée) the rice leaffolder".Pesticide Biochemistry and Physiology 81 (2): 113.doi:10.1016/j.pestbp.2004.10.004.
- Senthil-Nathan, S., Kalaivani, K., Murugan, K., Chung, P.G. (2005). "Effects of neem limonoids on malarial vector Anopheles stephensi Liston (Diptera: Culicidae)". Acta Tropica96 (1): 47. doi:10.1016/j.actatropica.2005.07.002.PMID 16112073.
University of Cambridge, UK
Synthesis of Azadirachtin: A Long but Successful Journey
Angew. Chem. Int. Ed. 2007, 46: 7629-7632
Conversion fairly high hurdle is followed thereafter. Barton-McCombie conditions and it has succeeded in building carbon skeleton of the right half be subjected to a radical cyclization reaction by. At a position that is crowded Then epoxidation and we have been. Becomes the conditions investigated thoroughly that (7 days) radical scavenger addition temperature (100 ℃ or more) time, it's easy to imagine that even just one step here, consider mind-boggling are stacked . Same compound obtained in Degradation Studies This is obtained, advances the synthesized according to the reverse route later, we have completed the synthesis of azadirachtin.