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Title: Studies on the structure of the insect feeding inhibitor azadirachtin
Author: Percy, G. R.
Awarding Body: Keele University
Current Institution: Keele University
Date of Award: 1972
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Azadirachtin C35H44O16, a locust feeding inhibitor, was first extracted from neem seeds by Butterworth in 1967. Butterworth identified two acetate esters, two carboxymethyl groups, a tiglate ester, two hydroxyl groups and a 2,3-dihydrofuran ring in the molecule. During the course of this present work an additional tertiary hydroxyl group and a tertiary methyl group have been detected, while a ketone carbonyl function and an ether linkage at the 2-position of the dihydrofuran system have been tentatively assigned. In this way all sixteen oxygen in the molecule have been accounted for. Furthermore, selenium dehydrogenation of an azadirachtin derivative has yielded methyl-napthalenes indicating the presence of two fused six-membered carbocyclic rings in the parent molecule. Various pieces of evidence are presented which suggest that azadirachtin contains a structural unit equivalent to the intact A and B rings of a limonoid, indeed it is suggested that azadirachtin may be a highly oxidised member of this naturally occurring class of compounds. A survey of the n.m.r. spectra of azadirachtin and several derivatives is presented. Thirty-three of the protons in the parent molecule are now definitely assigned and the n.m.r. signals for the remaining eleven protons are now recognised. In the later stages of this work attention was given to obtaining a crystalline derivative of azadirachtin which might be amenable to X-ray studies as it was felt that this would be the route by which the total structure and stereochemistry of the molecule would be solved. So far no crystalline derivative has been prepared despite a variety of approaches. Further work on the physiological activity of azadirachtin against a number of insect species is also reported.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry