Transcript Sesquiterpenes

Sesquiterpenes
Farnesane
2,6,10-Trimethyldodecane or farnesane, the parent
compound of about 10 000 sesquiterpenes known
to date.
The (E,E)-isomer of a-farnesene is a
component of the flavors and natural
coatings of apples, pears and other fruits.
Associated with (E)-b-farnesene, it also
occurs in several ethereal oils, for example
those of camomile, citrus, and hops.
Chamomile
Aldehydes such as a- and b- sinensal derived
from a- and b-farnesene contribute to the
flavor of the oil of orange expressed from the
fresh peel of ripe fruits of Citrus sinensis
(Rutaceae); mandarin peel oil from Citrus
reticulata and C. aurantium (Rutaceae)
contains 0.2% of a-sinensal with the smell of
oranges.
S)-(+)-Nerolidol in the oil of neroli )‫(زهر البرتقال‬
obtained from orange flowers and found in many
other flowers is used in perfumery, similar to farnesol
from Acacia farnensiana (Mimosaceae) and the oils
of bergamot, hibiscus, jasmine and rose, and
pleasantly smelling blossoms such as lily of the
valley.
(
Actinodaphne longifolia
Acacia farnensiana ‫السنط‬
‫المضعف او زنبق الوادي ‪Lily of the valley‬‬
Monocyclic Farnesane Sesquiterpenes
Cyclofarnesanes and Bisabolanes
Cyclofarnesanes formally arise when carbon
atoms C-6 and C-7 of farnesane close a ring.
Abscisic acid, occurring in the leaves of
cabbage, potatoes, roses, and young fruits of
cotton. Abscisic acid acts as an antagonist of
plant growth hormones and controls flowering,
falling of fruits and shedding of leaves.
(+)-dihydroxy-g-ionylidene acetic acid are
produced by the fungus Cercospora cruenta
which is antibacterially active
Formally, C-1 and C-6 of farnesane close a cyclohexane ring in the
bisabolanes, which represent a more prominent class of monocyclic
sesquiterpenes. Additional cyclizations increase the diversity. More
than 100 bisabolane derivatives of plant origin are known to date
Oil of ginger obtained from the rhizome of Zingiber officinalis
(Zingiberaceae) consists predominantly of (-)-zingiberene (2040%), b-sesquiphellandrene and (+)- b - bisabolene
Ginger rhizome
b-bisabolene
also occurs in Chamaecyparis nootkatensis
(Cupressaceae) and in the Sibirian pine tree Pinus sibirica (Pinaceae)
(+)-a- and (+)-b-bisabolol are fragrant sesquiterpenes found
in the essential oils of various plants; they also contribute to
the odors of camomile and of bergamot oil from unripe
fruits of Citrus aurantium var. bergamia (Rutaceae) growing
in southern Italy.
Schisandra chinensis
Germacranes and Elemanes
Germacranes formally result from ring closure of C-1 and
C-10 of farnesane. 1(10),4-Germacradienes such as
1(10),4-germacradien-6-ol present as a glycoside in
Pittosporum
tobira
may
ungergo
COPE
rearrangements to elemadienes, exemplified by
shyobunol from the oils of galbanum and kalmus, so
that some isolated elemane derivatives are supposed
to be artifacts arising from germacranes.
Pittosporum tobira
galbanum
kalmus
About 50 elemanes known to date comprise b-elemenone
from the oil of myrrh, representing the COPE rearrangement
product of germacrone, (-)-bicycloelemene from peppermint
oils of various provenance (e.g. Mentha piperita or Mentha
arvensis), and b-elemol which is not only a minor component
of Javanese( ‫(من جزيرة جاوة‬oil of citronella but is also found in
the elemi oil with an odor like pepper and lemon, expressed
from the Manila elemi resin of the tree Canarum luzonicum
(Burseraceae).
Humulanes
Ring closure of C-1 and C-11 of farnesane, not only
formally
but
also
in
biogenesis
via
farnesyldiphosphate, produces the sesquiterpene
skeleton of more than 30 naturally occurring
humulanes. Regioisomeric a- and b-humulene occur
in the leaves of Lindera strychnifolia (Lauraceae).
Lindera strychnifolia
tree Canarum luzonicum
(Burseraceae).
‫ نعناع حقلي‬Mentha arvensis