Chemistry Reference
In-Depth Information
O
OH
H
2
N
CO
2
H
HO
CO
2
H
HS
CO
2
H
OH
HO
NH
NH
2
NH
2
NH
2
4-Hydroxyproline
5-Hydroxylysine
Homoserine
Homocysteine
OH
CO
2
H
CO
2
H
CO
2
H
CO
2
H
H
2
N
H
2
N
H
2
N
NH
2
NH
2
Ornithine
β-Alanine
γ-Aminobutyric acid
(GABA)
Statine
FIGURE 7. 5
Examples of other “unusual” amino acids found in nature.
O
N
OH
O
O
NH
H
H
2
N
NH
HN
O
HN
OO
Ph
O
HN
O
HO
S
O
O
HN
N
N
N
N
N
H
O
H
2
N
H
O
O
O
Nt
FIGURE 7. 6
Structure of the cyclic peptide bacitracin.
Although the naturally occurring amino acids are chiral and exist in nature in the
L-form, there are many “unusual” amino acids, including the D-enantiomer forms
of some common amino acids, which are produced by microorganisms (Figure 7.5).
One of these amino acids is ornithine (shown in Figure 7.5) and is found as a com-
ponent of the cyclic peptide, known as bacitracin A (Figure 7.6). Cyclic peptides
possess antimicrobial activity and numerous compounds with varied numbers of
amino acids have been discovered. One extremely important cyclic peptide is vanco-
mycin (Figure 7.7). In view of the increasing resistance to frontline antibiotics, these
vancomycins are gaining an ever more prominent role in their use in countering
infectious diseases.
Search WWH ::
Custom Search