Longifolene

 ( Polycyclic Nonaromatic Hydrocarbons ) 

Longifolene is a common sesquiterpene. It is an oily liquid hydrocarbon found primarily in the high-boiling fraction of certain pine . 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 (optical rotation −42.73°) is found in small amounts in certain fungi and liverworts.

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Occurrence Terpentine obtained from Pinus longifolia (obsolete name for Pinus roxburghii Sarg.) 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. target="_blank" rel="nofollow"> Shan-Shan Yao； Wen-Fei Guo； YI Lu； Yuan-Xun Jiang, "Flavor Characteristics of Lapsang Souchong and Smoked Lapsang Souchong,a Special Chinese Black Tea with Pine Smoking Process", Journal of Agricultural and Food Chemistry, Vol. 53, No.22, (2005)

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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 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.

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Synthesis and related chemistry The laboratory characterization and synthesis of longifolene has long attracted attention.Naffa, P.; Ourisson, G. Bulletin de la Société chimique de France, 1954, 1410.Ho, Gregory J. Org. Chem. 2005, 70, 5139 -5143.

It reacts with borane to give the derivative dilongifolylborane, which is a chiral hydroboration agent.

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External links

• Longifolene Total Syntheses @ SynArchive.com

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