586
Chirality in Biology
CHO
C
2
H
OH
C
3
H
OH
CH
2
OH
CHO
C
2
H
OH
C
3
HO
H
C
4
HO
H
CH
2
OH
CHO
C
2
H
OH
C
3
HO
H
C
4
H
OH
C
5
H
OH
CH
2
OH
H
OH
O
HO
OH
HO
OH
H
OH
O
OH
OH
OH
OH
(a)
(b)
(c)
(d)
(e)
Fig. 5
Carbohydrate confgurations.
(
a
)
=
D-erythrose;
(
b
)
=
L-arabinose;
(
c
)
=
D-glucose. The D/L assignments are based
on the confgurations at C-3 For (a), C-4 For (b), and C-5 For (c);
these are the chiral carbon atoms with the highest number. ±or
D-g
lucose,zigzagconfgurations are shown as (d) (vertical) and
(e) (horizontal).
HO
OH
COCH
3
H
HO
OH
OH
OH
O
(a)
(b)
Fig. 6
Naturally occurring allenes.
(
a
)
=
‘‘grasshopper ketone’’;
(
b
)
=
neoxanthin (From
Lycopersicon
roots).
(Fig. 6a), is used by flightless grasshoppers
to repel predatory ants.
Certain carotenoids such as neoxanthin
(Fig. 6b) are allenes. Some eicosanoids
form allene oxides from fatty acid hy-
droperoxides by the action of allene ox-
ide synthase (EC 4.2.1.92, hydroperoxide
dehydratase). In turn, these allene oxides
can undergo cyclization to cyclopentenone
derivatives by allene oxide cyclase (EC
5.3.99.6). A speci±c example of an al-
lene oxide pathway is the biosynthesis
of jasmonic acid from
α
-linolenic acid
(Fig. 7). Certain tertiary
α
-allenic amines
inhibit mitochondrial monoamine oxidase
type B and the allene group chirality has
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