Chemistry Reference
In-Depth Information
2
1
3
Myrcene
4
4
3
Retinol
2
1
5
Limonene
4, 4-link
1
5
5
5
4
2
1
5
3
3
1
1
3
4
2
4
2
4
3
2
2
3
3
2
4
1
1
4
2
4
3
3
5
1
2
4
5
5
5
1
Carotenoids
FIGURE 4.7
Examples of various terpenoid molecules found in nature.
Some more naturally occurring terpenes are varied in structure; the complexity
and level of importance are indicated in Figure 4.7. They are formed by the linking
of isoprene units and eventually can combine to form naturally occurring molecules
known as the carotenoids, which will be discussed further in Chapter 11. This type
of terpene illustrates how the isoprene units are connected to form long chain poly-
unsaturated compounds including the 4-4 link.
4.2 SHIKIMATE PATHWAY
Shikimic acid (Figure 4.8) is a precursor for the aromatic amino acids, such as
phenylalanine, tyrosine, and tryptophan, leading to indoles, indole-like derivatives,
and alkaloids. Furthermore, the shikimic acid pathway leads to a large number of
phenolic compounds, notably, phenylpropanoids flavonoids, tannins, and lignins dis-
cussed in Chapter 6.
O
OH
HO
OH
OH
FIGURE 4.8
Structure of shikimic acid.
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