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1. C20 diterpenoids

2. C20 diterpenoids
Geranylgeranyl diphosphate,
 Which consists of four C5 “isoprene units” that are
joined
 “head-to-tail”
OPP

3. C20 diterpenoids

4. C20 diterpenoids
Geranylgeranyl pyrophosphate, the starting
material for the biosynthesis of diterpenes

5. C20 diterpenoids
Taxadiene: a tricyclic
diterpene

6. Examples of diterpene substances

7. Diterpenes
Diterpenes are a class of chemical
compounds composed of
two terpene units with the molecular
formula C20H32; they may also be
thought of as consisting of
four isoprene units. They are
biosynthesized by plants, animals and
fungi via the HMG-CoA reductase
pathway, with geranylgeranyl
pyrophosphate being a primary
intermediate.

8. Diterpenes nomenclature
• Groups and subgroups
• Based on pathways
• Classification
• IUPAC
• CAS
• Trivial name(derived from the structural family
 Or relate to natural source)

9. C20 diterpenoids
As other terpenoids, they are widespread in the plant
kingdom, and most of them biosynthetically derive from
geranylgeranyl diphosphate, which forms acyclic (phytanes),
bicyclic (labdanes, halimanes, clerodanes), tricyclic
(pimaranes, abietanes, cassanes, rosanes, vouacapanes,
podocarpanes), tetracyclic (trachylobanes, kauranes,
aphidicolanes, stemodanes, stemaranes, atisanes,
gibberellanes), and macrocyclic diterpenes (taxanes,
cembranes, daphnanes, tiglianes, ingenanes) according to the
cyclization that occurs.
Diterpenoids are divided into more than 45 classes; they are
also found in marine organisms, which provide interesting
skeletons such as elisapterane .

10. C20 diterpenoids
Diterpenoids are divided into more than 45 classes;
they are also found in marine organisms, which
provide interesting skeletons such as elisapterane .

11. C20 diterpenoids
Although they are widely distributed and clearly
biologically active, much less is known about diterpenoids
as a class. The discovery of paclitaxel, a taxane diterpenoid
from Taxus brevifolia (Pacific yew), has sparked renewed
interest in this family of compounds.
Diterpenoids are of sufficiently high molecular weight
compared with low-molecular-weight terpenoids that they
are not volatile; thus, they are odorless. They are very
lipophilic and tend to have strong flavors. They are
typically found in resins in plants, as is discussed later.
They do not tend to occur as glycosides. Little is known of
their pharmacokinetics, although presumably, they are well
absorbed orally, given their lipophilicity.

12. C20 diterpenoids
Select Diterpenoid-Rich Herbs
Coffea arabica (coffee)
Montanoa tomentosa (zoapatle)
Plectranthus barbatus (forskohlii,
coleus)
Taxus brevifolia (Pacific yew)
Teucrium chamaedrys (germander)
Vitex agnus castus (chaste tree)
Contains potentially hepatotoxic
neoclerodane diterpenoids.

13. Uses of C20 diterpenoids
Overall, the anticancer drug taxol, used in therapy against
ovarian, breast, and lung cancer, with its synthetic water-soluble
analogue taxotere, is an example of unusual structure discovered
from nature and used as medicine. Promising diterpenes are the
ginkgolides showing potent and selective antagonistic activity
toward platelet-activating factor increasing in conditions of
shock, burns, ulceration, and inflammation skin diseases. Also
used in therapy is the diterpene resiniferatoxin, an ultrapotent
vanilloid, isolated from the Euphorbia resiniferalatex, in clinical
trials for bladder hyperiflexia and diabetic neuropathy. The
diterpenes used in therapy will be described together with other
promising bioactive diterpenes with particular attention to those
isolated from plants. Other diterpenes used in therapy are the
ginkgolides, forskolin, and resiniferatoxin.

14. Uses of C20 diterpenoids
Diterpenes form the basis for biologically
important compounds such as retinol, retinal,
and phytol. They are known to be antimicrobial
and antiinflammatory.

15. HOME WORK
DISCUSS THE NOMECLATURE OF DITERPENOIDS