Longifolene is the common (or trivial) chemical name of a naturally occurring, 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,^[1] Pinus longifolia (obsolete name for Pinus roxburghii Sarg.)^[2]
Chemically, longifolene is a tricyclic sesquiterpene. This molecule is chiral, and 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.
Longifolene is used in organic synthesis for the preparation of dilongifolylborane,^[3] a chiral hydroborating agent.
Longifolene is also one of two most abundant aroma constituents of lapsang souchong tea, because the tea is smoked over pine Due to the compact tricyclic structure and lack of functional groups, Longifolene is an attractive target for research groups highlighting new synthetic methodologies. Notable syntheses are by Corey,^[5][6] McMurray,^[7] Johnson,^[8] Oppolzer,^[9] and Schultz.^[10]

Longifolene total synthesis by Corey

 

Author	Elias J. Corey
Publication year	1961
Synthesis type	Total synthesis
Number of steps	14 (linear)
References	J. Am. Chem. Soc. 1961, 83, 1251. J. Am. Chem. Soc. 1964, 86, 478.

 http://www.synarchive.com/syn/118

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 Total synthesis of Longifolene:

Reference:	Corey, E. J.; Ohno, M.; Mitra, R. B.; Vatakencherry, P. A. J. Am. Chem. Soc. 1964, 86, 478. DOI
Keywords:	Ketone → Ketal • CompE+-Ketone/Ketone+glycol • O-H → O-SO2R • Ketone → Ketal(thio) • Ketone → Alkyl-OH • Alkyl-OH → Ketone • Li-Me+Ketone • Ketone+Li-Alkyl • Dehydration → Ene • Wittig-alkyl+Ketone • Alkene → Diol-1,2 • CompNu-Alcohol/Alcohol+RSO2Cl • Pinacol • ConjAdd Enolate • Ketone enolate+Enone • Hydrogenolysis C-S • Ketone → CH2 •
Reagents:	Wieland-Miescher • Glycol • TsOH • PPh3=CH-Me • OsO4 • TsCl, Py • LiClO4 • Carbonate, calcium • HCl, H2O • NEt3 • NaCPh3 • MeI • Thiol, (CH2)2-SH • BF3·OEt2 • AlH4-Li+ • Hydrazine • CrO3 • MeLi • SOCl2 •

	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.
	(+)-Longifolene IUPAC name (1R,2S,7S,9S)- 3,3,7-trimethyl- 8-methylenetricyclo- [5.4.0.02,9]undecane Identifiers CAS number 475-20-7  ChemSpider 1406720  Jmol-3D images Image 1 SMILES [show] InChI [show] Properties Molecular formula C15H24 Molar mass 204.36 g/mol Density 0.928 g/cm3 Boiling point 254 °C (706 mm Hg)

 1,4-Methanoazulene, Junipen, (+)-Longifolene, 475-20-7, 3,3,7-trimethyl-8-methylenetricyclo[5.4.0.02,9]undecane, Kuromatsuen, Kuromatsuene 
Molecular Formula: C₁₅H₂₄   Molecular Weight: 204.35106
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The borane derivative dilongifolylborane is used in organic synthesis as a chiral hydroborating agent.^[12]

1. Naffa, P.; Ourisson, G. Bulletin de la Société chimique de France, 1954, 1410.
2. Simonsen, J. L. J. Chem. Soc. 1920, 117, 570.
3. Jadhav, P. K.; Brown, H. C. J. Org. Chem. 1981, 46, 2988.
4. 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)
5. Corey, E. J. et al. J. Am. Chem. Soc. 1961, 83, 1251.
6. Corey, E. J. et al. J. Am. Chem. Soc. 1964, 86, 478.
7. McMurray, J. E.; Isser, S. J. J. Am. Chem. Soc. 1972, 94, 7132.
8. Volkermann, R. A.; Andrews, G. C.; Johnson, W. S. J. Am. Chem. Soc. 1975, 97, 4777-4779.
9. Oppolzer, W.; Godel, T. J. Am. Chem. Soc. 1978, 100, 2583.
10. Schultz, A. G. et al. J. Org. Chem. 1985, 50, 915.
11. Ho, Gregory J. Org. Chem. 2005, 70, 5139 -5143.
12. Dev, Sukh (1981). "Aspects of longifolene chemistry. An example of another facet of natural products chemistry". Accounts of Chemical Research 14 (3): 82–88. doi:10.1021/ar00063a004.