Longifolene is a common

sesquiterpene Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many combinations. Biochemical modifications s ...

. It is an oily liquid

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and Hydrophobe, hydrophobic; their odor is usually fain ...

found primarily in the high-boiling fraction of certain pine

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

s. The name is derived from that of a

pine A pine is any conifer tree or shrub in the genus ''Pinus'' () of the family Pinaceae. ''Pinus'' is the sole genus in the subfamily Pinoideae. ''World Flora Online'' accepts 134 species-rank taxa (119 species and 15 nothospecies) of pines as cu ...

species from which the compound was isolated. It is a tricyclic chiral molecule. The

enantiomer In chemistry, an enantiomer (Help:IPA/English, /ɪˈnænti.əmər, ɛ-, -oʊ-/ Help:Pronunciation respelling key, ''ih-NAN-tee-ə-mər''), also known as an optical isomer, antipode, or optical antipode, is one of a pair of molecular entities whi ...

commonly found in pines and other higher plants exhibits a positive

optical rotation Optical rotation, also known as polarization rotation or circular birefringence, is the rotation of the orientation of the plane of polarization about the optical axis of linearly polarized light as it travels through certain materials. Circul ...

of +42.73°. The other enantiomer (optical rotation −42.73°) is found in small amounts in certain

fungi A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

and

liverworts Liverworts are a group of non-vascular plant, non-vascular embryophyte, land plants forming the division Marchantiophyta (). They may also be referred to as hepatics. Like mosses and hornworts, they have a gametophyte-dominant life cycle, in wh ...

Occurrence

Terpentine obtained from ''Pinus longifolia'' (obsolete name for ''

Pinus roxburghii ''Pinus roxburghii'', commonly known as chir pine or longleaf Indian pine, is a species of pine tree Native plant, native to the Himalayas. It was named after William Roxburgh. Description ''Pinus roxburghii'' is a large tree reaching with a ...

'' Sarg.) contains as much as 20% of longifolene. Longifolene is also one of two most abundant

aroma An odor (American English) or odour (Commonwealth English; see spelling differences) is a smell or a scent caused by one or more volatilized chemical compounds generally found in low concentrations that humans and many animals can perceive v ...

constituents of

lapsang souchong Lapsang souchong (; ) or Zhengshan xiaozhong (, 'Proper Mountain Small Varietal') is a black tea consisting of leaves that are smoke-dried over a pinewood fire. This smoking is accomplished either as a cold smoke of the raw leaves as they are ...

tea, because the tea is smoked over pinewood fires.

Biosynthesis

The biosynthesis of longifolene begins with farnesyl diphosphate (1) (also called farnesyl pyrophosphate) by means of a cationic polycyclization cascade. Loss of the pyrophosphate group and cyclization by the distal

alkene In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

gives intermediate 3, which by means of a 1,3-hydride shift gives intermediate 4. After two additional cyclizations, intermediate 6 produces longifolene by a 1,2-alkyl migration.

Synthesis and related chemistry

The laboratory characterization and synthesis of longifolene has long attracted attention. It reacts with

borane Borane is an inorganic compound with the chemical formula . Because it tends to dimerize or form adducts, borane is very rarely observed. It normally dimerizes to diborane in the absence of other chemicals. It can be observed directly as a c ...

to give the derivative dilongifolylborane, which is a chiral hydroborating agent.

References

External links

Longifolene Total Syntheses @ SynArchive.com
{{Terpenes Polycyclic nonaromatic hydrocarbons Sesquiterpenes Total synthesis