Natural insecticide re-created in the lab. Success after 22 years of research: synthesis of
azadirachtin.
Twenty-two years of dedicated research has finally resulted in success:
In the journal Angewandte Chemie, a British team headed by Steven V. Ley
at the University of Cambridge reports the first synthesis of
azadirachtin, a natural compound that stops predatory insects from
feeding.
Plants have a variety of defense mechanisms to deter
insect attack. Investigation of these mechanisms often allows
researchers to discover molecules with interesting biological properties.
One such compound is azadirachtin, which was first isolated from the
neem tree (also known as the Indian lilac) in 1968. The name of this
natural product is derived from the botanical name of the plant,
Azadiracta indica. Azadirachtin is a highly active substance that
inhibits the development of the larvae of a broad spectrum of
destructive insects but is harmless to mammals and beneficial insects,
such as bees and ladybugs.
The structure of this complicated molecule was
published in 1985, after a long, intensive research effort, but all
attempts to make this compound have thus far been unsuccessful. The
difficulty of the synthesis stems in part from the 16 stereocenters in
the molecule, the complex pattern of oxygen-containing functional
groups, and a conformation and reactivity that are strongly dependent
on intramolecular bridging hydrogen bonds. The compound is highly
light sensitive and can readily undergo structural rearrangement.
Ley and his team have been interested in solving
the problem of the synthesis of this compound for 22 years. Their
endurance has now been abundantly rewarded. The key steps in making
this molecule involve a Claisen rearrangement and a novel radical
cyclization reaction.
�While we have been working on this complex
synthesis,� says Ley, �we have also developed a number of new methods
that are of general use for the construction of other important
molecules.� Ley expects that using the successful synthetic route will
allow the development of simpler derivatives of azadirachtin that are
stable and may lead to a new generation of environmentally acceptable
insecticides.
Further Information and Source:
-
Gemma E. Veitch, Edith Beckmann, Dr., Brenda J. Burke, Dr., Alistair
Boyer, Carles Ayats, Dr., Steven V. Ley, Prof. Dr. -
A Relay Route for the Synthesis of Azadirachtin - Angewandte
Chemie 2007, 119, No. 40, doi: 10.1002/ange.200703028
