Longifolene is the common (or trivial) chemical name of a naturally occurring, oily liquid
hydrocarbonIn organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon and hydrogen are referred to as "pure"...
found primarily in the high-boiling fraction of certain pine
resinResin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume. Fossilized resins are the source of amber...
s. The name is derived from that of a
pinePines are coniferous trees in the genus Pinus , in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Distribution:...
species from which the compound was isolated,
Pinus longifolia (obsolete name for
Pinus roxburghii Sarg.)
Chemically, longifolene is a tricyclic
sesquiterpeneTerpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium....
. This molecule is
chiralThe term chiral is used to describe an object that is non-superposable on its mirror image. Achiral objects are objects that are identical to their mirror image....
, and the
enantiomerIn stereochemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are "non-superposable" , much as one's left and right hands are "the same" but opposite....
commonly found in pines and other higher plants exhibits a positive
optical rotationOptical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose , solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms or...
of +42.73°.
Longifolene is the common (or trivial) chemical name of a naturally occurring, oily liquid
hydrocarbonIn organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. With relation to chemical terminology, aromatic hydrocarbons or arenes, alkanes, alkenes and alkyne-based compounds composed entirely of carbon and hydrogen are referred to as "pure"...
found primarily in the high-boiling fraction of certain pine
resinResin is a hydrocarbon secretion of many plants, particularly coniferous trees. It is valued for its chemical constituents and uses, such as varnishes and adhesives, as an important source of raw materials for organic synthesis, or for incense and perfume. Fossilized resins are the source of amber...
s. The name is derived from that of a
pinePines are coniferous trees in the genus Pinus , in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Distribution:...
species from which the compound was isolated,
Pinus longifolia (obsolete name for
Pinus roxburghii Sarg.)
Chemically, longifolene is a tricyclic
sesquiterpeneTerpenes are a large and varied class of hydrocarbons, produced primarily by a wide variety of plants, particularly conifers, though also by some insects such as termites or swallowtail butterflies, which emit terpenes from their osmeterium....
. This molecule is
chiralThe term chiral is used to describe an object that is non-superposable on its mirror image. Achiral objects are objects that are identical to their mirror image....
, and the
enantiomerIn stereochemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are "non-superposable" , much as one's left and right hands are "the same" but opposite....
commonly found in pines and other higher plants exhibits a positive
optical rotationOptical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose , solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms or...
of +42.73°. The other enantiomer (optical rotation −42.73°) is found in small amounts in some primitive plants like fungi and liverworts.
Longifolene is used in organic synthesis for the preparation of dilongifolylborane, a chiral
hydroboratingIn organic chemistry, the hydroboration-oxidation reaction is a two-step organic chemical reaction that converts an alkene into a neutral alcohol by the net addition of water across the double bond. The hydrogen and hydroxyl group are added in a syn addition leading to cis stereochemistry...
agent.
Total syntheses
Due to the compact tricyclic structure and lack of
functional groupIn organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction regardless of the size of the molecule it is a part...
s, Longifolene is an attractive target for research groups highlighting new synthetic methodologies. Notable syntheses are by
CoreyElias James Corey is an American organic chemist. In 1990 he won the Nobel Prize in Chemistry "for his development of the theory and methodology of organic synthesis", specifically retrosynthetic analysis...
, McMurray, Johnson, Oppolzer, and Schultz.
The Johnson biosynthesis has since been validated as feasible using modern quantum mechanical computational methods. The subsequent cationic cascade mechanism has been shown to go through a non-classical cation intermediate.
Biosynthesis
The biosynthesis of longifolene begins with farnesyl diphosphate (
1) (also called
farnesyl pyrophosphateFarnesyl pyrophosphate is an intermediate in the HMG-CoA reductase pathway used by organisms in the biosynthesis of terpenes and terpenoids....
) by means of a cationic polycyclization cascade. Loss of the pyrophosphate group and cyclization by the distal
alkeneIn organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
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 migrationA 1,2-rearrangement or 1,2-migration or 1,2-shift or Whitmore 1,2-shift is an organic reaction where a substituent moves from one atom to another atom in a chemical compound. In a 1,2 shift the movement involves two adjacent atoms but moves over larger distances are possible...
.