Azadirachtin 印楝素
Azadirachtin 印楝素
Azadirachtin
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Azadirachtin
Azadirachtin.png
Azadirachtin model.png
Names
IUPAC name
Dimethyl
(2aR,3S,4S,R,S,7aS,8S,10R,10aS,10bR)-10-(acetyloxy)-3,5-dihydroxy-4-[(1S,2S,6S,8S,9R,11S)-2-hydroxy-11-methyl-5,7,10-trioxatetracyclo[6.3.1.02,6.09,11]dodec-3-en-9-yl]-4-methyl-8-{[(2E)-2-methylbut-2-enoyl]oxy}octahydro-1H-furo[3',4':4,4a]naphtho[1,8-bc]furan-5,10a(8H)-dicarboxylate
Other names
Dimethyl
(2aR,3S,4S,4aR,5S,7aS,8S,10R,10aS,10bR)-10-acetoxy-3,5-dihydroxy-4-[(1aR,S,3aS,6aS,7S,7aS)-6a-hydroxy-7a-methyl-3a,6a,7,7a-tetrahydro-2,7-methanofuro[2,3-b]oxireno[e]oxepin-
1a(2H)-yl]-4-methyl-8-{[(2E)-2-methylbut-2-enoyl]oxy}octahydro-1H-naphtho[1,8a-c:4,5-b'c']difuran-5,10a(8H)-dicarboxylate
Identifiers
CAS Number
11141-17-6 Yes
3D model (JSmol)
Interactive image
ChEBI
CHEBI:2942 Yes
ChemSpider
4444685 Yes
ECHA InfoCard 100.115.924
KEGG
C08748 Yes
PubChem CID
5281303
InChI[show]
SMILES[show]
Properties
Chemical formula
C35H44O16
Molar mass 720.72
g·mol−1
Except where otherwise noted, data are
given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes verify (what is YesNo ?)
Infobox references
Azadirachtin, a chemical compound belonging
to the limonoid group, is a secondary metabolite present in neem seeds. It is a
highly oxidized tetranortriterpenoid which boasts a plethora of oxygen-bearing
functional groups, including an enol ether, acetal, hemiacetal,
tetra-substituted epoxide and a variety of carboxylic esters.
Contents
1 Chemical
synthesis
2 Occurrence
and use
3 Biosynthesis
4 See
also
5 References
6 External
links
Chemical synthesis
Azadirachtin has a complex molecular
structure; it presents both secondary and tertiary hydroxyl groups and a
tetrahydrofuran ether in its molecular structure, alongside 16 stereogenic
centres, 7 of which are tetrasubstituted. These characteristics explain the
great difficulty encountered when trying to prepare this compound from simple
precursors, using methods of synthetic organic chemistry.
Hence, the first total synthesis was
published over 22 years after the compound's discovery: this first synthesis
was completed by the research group of Steven Ley at the University of
Cambridge in 2007.[1][2] The described synthesis was a relay approach, with the
required, heavily functionalized decalin intermediate being made by total
synthesis on a small scale, but being derived from the natural product itself
for the gram-scale operations required to complete the synthesis.
Occurrence and use
Initially found to be active as a feeding
inhibitor towards the desert locust (Schistocerca gregaria),[3] it is now known
to affect over 200 species of insects, by acting mainly as an antifeedant and
growth disruptor. It was recently found that azadirachitin possesses
considerable toxicity towards African cotton leafworm (Spodoptera littarolis),
which are resistant to a commonly used biological pesticide, Bacillus
thuringiensis. Azadirachtin fulfills many of the criteria needed for a good
insecticide. 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).
This compound is found in the seeds (0.2 to
0.8 percent by weight) of the neem tree, Azadirachta indica (hence the prefix
aza does not imply an aza compound, but refers to the scientific species name).
Many more compounds, related to azadirachtin, are present in the seeds as well
as in the leaves and the bark of the neem tree which also show strong
biological activities among various pest insects [4][5] Effects of these
preparations on beneficial arthropods are generally considered to be minimal.
Some laboratory and field studies have found neem extracts to be compatible
with biological control. Because pure neem oil contains other insecticidal and
fungicidal compounds in addition to azadirachtin, it is generally mixed at a
rate of 1 ounce per gallon (7.8 ml/l) of water when used as a pesticide.
Azadirachtin is the active ingredient in
many pesticides including TreeAzin,[6] AzaMax,[7] BioNEEM,[8] AzaGuard,[9] and
AzaSol[10], Terramera Proof and Terramera Cirkil.
Azadirachtin has a synergistic effect with
the biocontrol agent Beauveria.[11]
Biosynthesis
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 C27 steroid. 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.
Apotirucallol becomes a
tetranortriterpenoid when the four terminal carbons from the side chain are
cleaved off. The remaining carbons on the side chain cyclize to form a furan
ring and the molecule is oxidized further to form azadirone and azadiradione. The
third ring is then opened and oxidized to form the C-seco-limonoids such as
nimbin, nimbidinin and salannin, which has been esterified with a molecule of
tiglic acid, which is derived from L-isoleucine. It is currently proposed that
the target molecule is arrived at by biosynthetically converting azadirone into
salanin, which is then heavily oxidized and cyclized to reach azadirachtin.
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