O
O
H
H
O
O
H
O
(+)-Limonene, a monoterpene
Artemisinin,
An antimalarial sesquiterpene
O
O
O
OH
OH
H
OH
O
O
H
H
Forskolin
An antihypertensive diterpene
α-Amyrin
A pentacyclic triterpene
β-Carotene
A tetraterpene
6.5.2 Biosynthesis
3R-(þ)-mevalonic acid is the precursor of all terpenoids. The enzymes
mevalonate kinase and phosphomevalonate kinase catalyse phosphorylation of mevalonic acid to yield 3R-(þ)-mevalonic acid 5-diphosphate,
which is finally transformed to isopentenyl diphosphate, also known as
isopentenyl pyrophosphate (IPP), by the elimination of a carboxyl and a
hydroxyl group mediated by mevalonate 5-diphosphate decarboxylase.
Isopentenyl pyrophosphate is isomerized by isopentenyl isomerase to
dimethylallylpyrophosphate (DMAPP). A unit of IPP and a unit of
DMAPP are combined together head to tail by dimethylallyl transferase
to form geranyl pyrophosphate, which is finally hydrolysed to geraniol, a
simple monoterpene. Geranyl pyrophosphate is the precursor of all monoterpenes.
In similar fashions, the core pathway up to C 25 compounds (five isoprene
units) is formed by sequential addition of C 5 moieties derived from IPP to a
starter unit derived from DMAPP. Thus, sesquiterpenes are formed form the
precursor 2E, 6E-farnesyl pyrophosphate (FPP), and diterpenes from 2E, 6E,
10E-geranylgeranyl pyrophosphate (GGPP). The parents of triterpenes and
tetraterpenes are formed by reductive coupling of two FPPs or GGPPs,
respectively. Rubbers and other polyisoprenoids are produced from repeated
additions of C 5 units to the starter unit GGPP.
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CH6 NATURAL PRODUCT CHEMISTRY
O
H
H
O
O
H
O
(+)-Limonene, a monoterpene
Artemisinin,
An antimalarial sesquiterpene
O
O
O
OH
OH
H
OH
O
O
H
H
Forskolin
An antihypertensive diterpene
α-Amyrin
A pentacyclic triterpene
β-Carotene
A tetraterpene
6.5.2 Biosynthesis
3R-(þ)-mevalonic acid is the precursor of all terpenoids. The enzymes
mevalonate kinase and phosphomevalonate kinase catalyse phosphorylation of mevalonic acid to yield 3R-(þ)-mevalonic acid 5-diphosphate,
which is finally transformed to isopentenyl diphosphate, also known as
isopentenyl pyrophosphate (IPP), by the elimination of a carboxyl and a
hydroxyl group mediated by mevalonate 5-diphosphate decarboxylase.
Isopentenyl pyrophosphate is isomerized by isopentenyl isomerase to
dimethylallylpyrophosphate (DMAPP). A unit of IPP and a unit of
DMAPP are combined together head to tail by dimethylallyl transferase
to form geranyl pyrophosphate, which is finally hydrolysed to geraniol, a
simple monoterpene. Geranyl pyrophosphate is the precursor of all monoterpenes.
In similar fashions, the core pathway up to C 25 compounds (five isoprene
units) is formed by sequential addition of C 5 moieties derived from IPP to a
starter unit derived from DMAPP. Thus, sesquiterpenes are formed form the
precursor 2E, 6E-farnesyl pyrophosphate (FPP), and diterpenes from 2E, 6E,
10E-geranylgeranyl pyrophosphate (GGPP). The parents of triterpenes and
tetraterpenes are formed by reductive coupling of two FPPs or GGPPs,
respectively. Rubbers and other polyisoprenoids are produced from repeated
additions of C 5 units to the starter unit GGPP.
332
CH6 NATURAL PRODUCT CHEMISTRY