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ALKALOID BIOSYNTHESIS

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papaverine. the 'poppy' alkaloid. just different in hydroxylation. and methylation patterns ... papaverine. laudanosine. laudanine. laudanosoline. coclaurine ... – PowerPoint PPT presentation

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Title: ALKALOID BIOSYNTHESIS


1
ALKALOID BIOSYNTHESIS
2
MOST ALKALOIDS ARE DERIVED FROM a-AMINO ACIDS
SOME OF THE MAJOR RELATIONSHIPS ARE SHOWN BELOW
ornithine
tryptophan
lysine
and
and
R H phenylalanine
R OH tyrosine
R H, CH3
R H, alkyl
3
A COUPLE OF THE b-AMINO ACIDS ARE
SOMETIMES INVOLVED IN ALKALOID PRODUCTION ALSO
These b-amino acids are
nicotinic acid
anthranilic acid
.. more later
4
FORMATION OF ISOQUINOLINE ALKALOIDS
decarboxylation
hydroxylation
1
2
..
3
Mannich reaction and aromatic substitution
..

4
5
..


..
Enz-B
imine formation
6,7,8
methylation
5
AROMATIC SUBSTITUTION !
STEPS 4-5 ARE AROMATIC SUBSTITUTION USING AN
ACTIVATED (-OH) RING

..
..

()
para substitution
()
()
E
benzenium ion
B
..

4
5
..


..
Enz-B
6
MANNICH REACTION
7
MANNICH REACTION
one pot reaction - everything added at once
..


aldehyde
dialkylamine
enolate component
(has an acidic a-hydrogen)
second mole of R2NH takes H

..
..
-
iminium ion
..
like an aldol condensation

The aromatic substitution step shown earlier cam
also be regarded as a Mannich reaction.
8
WHERE DO THE ALDEHYDES COME FROM ?
..
3
9
WHERE DO THE ALDEHYDES COME FROM ?
AMINO ACIDS ARE ONE SOURCE !
PLP
- CO2
O
- NH2
phenylalananine or tyrosine
phenylacetaldehyde or p -hydroxyphenylacetaldehyde

PLP
- CO2
O
- NH2
acetaldehyde
alanine
The aldehydes can be produced from the B6
decarboxylation-deamination-oxidation of a-amino
acids - or may be produced in other biochemical
pathways from which they can be siphoned off.
Other amino acids can also be used.
Process 2 !
10
()-DEMETHYLCOCLAURINE
BIOSYNTHESIS OF A MORE COMPLICATED
ALKALOID
11
()-DEMETHYLCOCLAURINE
A TYPICAL BENZYLISOQUINOLINE ALKALOID
if R H ()-Demethylcoclaurine
found in the lotus plant
Nelumbo nucifera
if R OH norlaudanosoline
found in poppy spp
papaverine
the poppy alkaloid
just different in hydroxylation and methylation
patterns
12
LOTUS
spp
Water Lily
13
CALIFORNIA POPPIES
Papaver spp
14
BIOSYNTHESIS OF ()-DEMETHYLCOCLAURINE
tyrosine
a benzylisoquinoline alkaloid
PLP (B6)
PLP (B6)
hydroxylase
hydroxylase
(SAM)
Mannich (Arom Subst)

iminium ion
15
CHEMICAL SYNTHESIS OF ANHALAMINE
Chemists have always liked the challenge of
natural product synthesis.
Sometimes it is done for the love of
the challenge, but sometimes it is a
required part of a structure proof.
16
Mescaline is the most abundant of the
peyote alkaloids and was selected as the
obvious starting material.
Its structure was already well-established.
17
mescaline
..
..
H2SO4
HCl
HCl
NaOH

selective due to internal H-bonding
LiAlH4
Pd-C
H2
anhalamine
Brossi, Schenker and Leimgruber (1964)
18
SOME OTHER SIMPLE ISOQUINOLINE ALKALOIDS
19
SOME OTHER ISOQUINOLINE ALKALOIDS
()-demethylcoclaurine
papaverine
laudanosine
Nelumbo nucifera
(lotus, water lily)
laudanine
laudanosoline
coclaurine
Papaver spp
(poppies)
Cocculus laurifolius
(evergreen shrub)
20
ASSIGNMENTS
Lime Problem and Cherry Problem
Due in one week
F Oct. 19, 2007
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