Longifolene
Longifolene is a common sesquiterpene. It is an oily liquid hydrocarbon found primarily in the high-boiling fraction of certain pine resins. The name is derived from that of a pine species from which the compound was isolated. It is a tricyclic chiral molecule. The enantiomer commonly found in pines and other higher plants exhibits a positive optical rotation of +42.73°. The other enantiomer is found in small amounts in certain fungi and liverworts.
Occurrence
Terpentine obtained from Pinus longifolia contains as much as 20% of longifolene.Longifolene is also one of two most abundant aroma constituents of lapsang souchong tea, because the tea is smoked over pinewood fires.
Biosynthesis
The biosynthesis of longifolene begins with farnesyl diphosphate by means of a cationic polycyclization cascade. Loss of the pyrophosphate group and cyclization by the distal alkene 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.[Image:Longifolene Biosynthesis Mechanism.png|center|600px|The biosynthesis of longifolene]
Synthesis and related chemistry
The laboratory characterization and synthesis of longifolene has long attracted attention.| Longifolene total synthesis by Corey |
It reacts with borane to give the derivative dilongifolylborane, which is a chiral hydroborating agent.