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.[3]
The laboratory synthesis of longifolene has attracted much syntheses.[4][5][6][7][8][9][10]
Longifolene total synthesis by Corey.svg
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.
^Corey, E. J.; Ohno, Masaji.; Mitra, Rajat B.; Vatakencherry, Paul A. (February 1964). "Total Synthesis of Longifolene". Journal of the American Chemical Society. 86 (3): 478–485.
doi:
10.1021/ja01057a039.
^McMurry, John E.; Isser, Stephen J. (October 1972). "Total synthesis of longifolene". Journal of the American Chemical Society. 94 (20): 7132–7137.
doi:
10.1021/ja00775a044.
^Volkmann, Robert A.; Andrews, Glenn C.; Johnson, William S. (August 1975). "Novel Synthesis of Longifolene". Journal of the American Chemical Society. 97 (16): 4777–4779.
doi:
10.1021/ja00849a062.
^Oppolzer, Wolfgang; Godel, Thierry (April 1978). "A New and Efficient Total Synthesis of (.+-.)-longifolene". Journal of the American Chemical Society. 100 (8): 2583–2584.
doi:
10.1021/ja00476a071.
^Schultz, Arthur G.; Puig, Salvador (March 1985). "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. 50 (6): 915–916.
doi:
10.1021/jo00206a049.
^Bo, Lei; Fallis, Alex G. (May 1990). "Direct total synthesis of (+)-longifolene via an intramolecular Diels-Alder strategy". Journal of the American Chemical Society. 112 (11): 4609–4610.
doi:
10.1021/ja00167a105.
^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.