The class of organic compounds called isoprenoids encompasses over 50,000 compounds. All structures in this class can be analyzed in terms of their isoprene subunits (a 5 carbon alkene) [1]. This diverse class of compounds includes cholesterol, rubber, and vitamin A. Currently most industrial uses for isoprenoids are in pharmaceutical, flavor, and perfume sectors. Most of the higher order isoprenoids commercially available are isolated from oils from the natural source; however, several simpler compounds, such as some monoprenes, are synthetically produced [2].

The biosynthesis of all isoprenoids are derived from 2 common precursors: isopentenyl diphosphate and dimethylallyl diphosphate. In nature, two distinct pathways are known. The mevalonate pathway (MEP) is well-known and occurs in eukaryotes and some gram positive prokaryotes. The second pathway, the deoxyxylulose-5-phosphate pathway (DXP), was fully characterized in 2002 [3]. Isoprenoids have been cited as a possible fuel source by a few corporations, although the proposed compounds have not been released [4].

[1] http://www.britannica.com/eb/article-9042964/isoprenoid
[2] Erman, W. F., 1985, Chemistry of the Monoterpenes: An Encyclopedic Handbook, Part A, pp. 3-15, Marcel Dekker, Inc., New York.
[3] Withers, S. T., Keasling, J. D., 2007, Appl Microbiol Biotechnol. 73, 980-990
[4] http://www.economist.com/science/displaystory.cfm?story_id=9861379%20%00