Longifolene Explained

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] 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 also one of two most abundant aroma constituents of lapsang souchong tea, because the tea is smoked over pinewood fires.^[2]

Occurrence and syntheses

Terpentine obtained from Pinus longifolia (obsolete name for Pinus roxburghii Sarg.) contains as much as 20% of longifolene.

The laboratory synthesis of longifolene has attracted much syntheses.^{[3] [4] [5] [6] [7] [8] [9]}

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.

Reactions

It reacts with borane to give the derivative dilongifolylborane, which is a chiral hydroborating agent.^[10]

External links

• Longifolene Total Syntheses @ SynArchive.com

Notes and References

1. Naffa, P.; Ourisson, G. Bulletin de la Société chimique de France, 1954, 1410.
2. http://d.wanfangdata.com.cn/NSTLQK_NSTL_QK10615205.aspx 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)
3. Corey. E. J.. Ohno. Masaji.. Mitra. Rajat B.. Vatakencherry. Paul A.. Total Synthesis of Longifolene. Journal of the American Chemical Society. February 1964. 86. 3. 478–485. 10.1021/ja01057a039.
4. McMurry. John E.. Isser. Stephen J.. Total synthesis of longifolene. Journal of the American Chemical Society. October 1972. 94. 20. 7132–7137. 10.1021/ja00775a044.
5. Volkmann. Robert A.. Andrews. Glenn C.. Johnson. William S.. Novel Synthesis of Longifolene. Journal of the American Chemical Society. August 1975. 97. 16. 4777–4779. 10.1021/ja00849a062.
6. Oppolzer. Wolfgang. Godel. Thierry. A New and Efficient Total Synthesis of (.+-.)-longifolene. Journal of the American Chemical Society. April 1978. 100. 8. 2583–2584. 10.1021/ja00476a071.
7. Schultz. Arthur G.. Puig. Salvador. The Intramolecular Diene-Carbene Cycloaddition Equivalence and an Enantioselective Birch Reduction-Alkylation by the Chiral Auxiliary Approach. Total Synthesis of (.+-.)- and (−)-Longifolene. The Journal of Organic Chemistry. March 1985. 50. 6. 915–916. 10.1021/jo00206a049.
8. Bo. Lei. Fallis. Alex G.. Direct total synthesis of (+)-longifolene via an intramolecular Diels-Alder strategy. Journal of the American Chemical Society. May 1990. 112. 11. 4609–4610. 10.1021/ja00167a105.
9. Ho, Gregory J. Org. Chem. 2005, 70, 5139 -5143.
10. Dev, Sukh . Aspects of Longifolene chemistry. An example of another Facet of natural products chemistry . Accounts of Chemical Research . 1981 . 14 . 3 . 82–88 . 10.1021/ar00063a004.