(+)-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 Y
SMILES	C=C1C3(C)C2CC C1C2C(C)(C)CCC3
Properties
Molecular formula	C15H24
Molar mass	204.36 g/mol
Density	0.928 g/cm3
Boiling point	254 °C (706 mm Hg)
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

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 some primitive plants like 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, due to the fact that the tea is smoked over pine fires.^[4]

[edit] Total syntheses

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].

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.^[11]

[edit] 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.

[edit] References

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, 2584.
10. ^ Schultz, A. G. et al. J. Org. Chem. 1985, 50, 915.
11. ^ Ho, Gregory J. Org. Chem. 2005, 70, 5139 -5143.

• Dev, S. Acc. Chem. Res. 1981, 14, 82-88.