Bergamotene
Bergamotenes are a group of isomeric chemical compounds with the molecular formula CH. The bergamotenes are found in a variety of plants, particularly in their essential oils. There are two structural isomers, α-bergamotene and β-bergamotene, which differ only by the location of a double bond. Both of these isomers have stereoisomers, the most common of which are known as the "cis" and "trans"-isomers (or endo- and exo-isomers). α-Bergamotene is found in the oils of carrot, bergamot, lime, citron, cottonseed, and kumquat. Pheromones. The bergamotenes are pheromones for some insects. For example, β-"trans"-bergamotene is a pheromone  for the wasp "Melittobia digitata". Plants can defend themselves against attack by herbivorous insects by producing pheromones such as bergamotenes that attract predators of those herbivores. In a more complex relationship, the tobacco plant "Nicotiana attenuata" emits α-"trans"-bergamotene from its flowers at night to attract the tobacco hawk moth ("Manduca sexta") as a pollinator; however, during the day the leaves produce α-"trans"-bergamotene to lure predatory insects to feed on any larvae and eggs that the pollinator may have produced. Biosynthesis. All the bergamotenes are biosynthesized from farnesyl pyrophosphate via a variety of enzymes including exo-alpha-bergamotene synthase, (+)-endo -beta-bergamotene synthase, (-)-endo-alpha-bergamotene synthase, and others. Bergamotenes, in turn, are intermediates in the biosynthesis of more complex chemical compounds. For example, β-"trans"-bergamotene is a precursor in the biosynthesis of fumagillin, ovalicin, and related antibiotics.