Chemistry Reference
In-Depth Information
Figure 1.10
Chemical diversity of monocyclic sesquiterpenoids.
zerumbeticum
, Zingiberaceae). Bicyclic sesquiterpenoids are formed because
of two carbon-carbon bonds, each linking two carbon atoms of the farnesane
skeleton together.
1.4.4 Diterpenoids
The diterpenoids, which contain 20 carbon atoms, are represented by acyclic,
monocyclic, bicyclic, tricyclic, and tetracyclic structures. Over 5,000 naturally
occurring diterpenoids, many of which frequently occur in plant families Arali-
aceae, Asteraceae, Cistaceae, Cupressaceae, Euphorbiaceae, Leguminosae, Labi-
atae, and Pinaceae, are known (32). The acyclic diterpenoid alcohol phytol (
J1
)
(Fig. 1.11) is a part of the structure of chlorophyll. A group of monocyclic diter-
penoids with a 14-carbon macrocyclic ring called cembranes [e.g., cembrene A
(
J2
)] also occurs in plants and is represented by over 100 members (32). Among
the other cyclic diterpenoids, the most abundant in plants are the bicyclic lab-
danes [e.g., (
)-forskolin (
J3
)], tricyclic abietanes [e.g., abietic acid (
J4
)], and
tetracyclic kauranes [e.g., (
−
)-kaurane (
J5
)], represented respectively by 500,
200, and 100 members (32). Baccatin III (
J6
), which is the diterpenoid part of
the well-known anticancer drug paclitaxel (Taxol
®
; Mead Johnson, Princeton,
NJ), contains a tricyclic skeleton derived from cembrane.
−
1.4.5 Triterpenoids and Steroids
Triterpenoids and steroids are groups of natural products that contain about
30 carbon atoms. They have a common origin, and their structures can be
