Sesquiterpene
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Sesquiterpenes consist of three isoprene units and have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be acyclic or contain rings, including many unique combinations.
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[edit] Acyclic
When geranyl pyrophosphate reacts with IPP, the result is the 15-carbon farnesyl pyrophosphate which is an intermediate in the biosynthesis of sesquiterpenes such as farnesene. Oxidation can then provide sesquiterpenoids such as farnesol.
[edit] Monocyclic
With the increased chain length and additional double bond, the number of possible ways that cyclization can occur is also increased and there exist a wide variety of cyclic sesquiterpenes. In addition to common six-membered ring systems such as is found in zingiberene, a consitituent of the oil from ginger, cyclization of one end of the chain to the other end can lead to macrocyclic rings such as humulene.
[edit] Bicyclic
In addition to common six-membered rings such as in the cadinenes, one classic bicyclic sesquiterpene is caryophyllene, from the oil of cloves, which has a nine-membered ring and cyclobutane ring. Additional unsaturation provides aromatic bicyclic sesquiterpenoids such as vetivazulene and guaiazulene.
[edit] Tricylic
With the addition of a third ring, the possible structures become increasingly varied. Examples include longifolene, copaene and the alcohol patchoulol.pl:Seskwiterpeny
