Terpineol is any of four isomericmonoterpenoids. Terpenoids are terpene that are modified by the addition of a functional group, in this case, an alcohol. Terpineols have been isolated from a variety of sources such as cardamom, cajuput oil, pine oil, and petitgrain oil.[1] Four isomers exist: α-terpineol, β-terpineol, γ-terpineol, and terpinen-4-ol. β-Terpineol and γ-terpineol differ only by the location of the double bond. Terpineol is usually a mixture of these isomers with α-terpineol as the major constituent.
File:Terpineols.svgTerpineols: alpha-, beta-, gamma-, and the 4-terpineol isomer
Terpineol has a pleasant odor similar to lilac and is a common ingredient in perfumes, cosmetics, and flavors. α-Terpineol is one of the two most abundant aroma constituents of lapsang souchong tea; the α-terpineol originates in the pine smoke used to dry the tea.[2] (+)-α-Terpineol is a chemical constituent of skullcap.
α-Terpineol has an aroma described as "pine, terpenic, lilac, citrus, woody, floral, resinous, cooling, lemon, lime".[3] Whilst both enantiomers of α-terpineol exhibit a floral lilac aroma,[4][5] the laevo form (−)-α-terpineol, is reportedly more terpenic. The aroma of β-terpineol is described as "pungent, earthy, woody".[6]. The aroma of γ-terpineol is "pine, floral, lilac".[7] The aroma of 4-terpinenol (also known as terpinen-4-ol or 4-carvomenthenol), is described as "peppery, woody, earthy, musty, sweet, mentholic, citrus, terpenic, spicy".[8]
Synthesis and biosynthesis
Although it is naturally occurring, terpineol is commonly manufactured from alpha-pinene, which is hydrated in the presence of sulfuric acid.[9]
The biosynthesis of α-terpineol proceeds from geranyl pyrophosphate, which releases pyrophosphate to give the terpinyl cation. This carbocation is the precursor to many terpenes and terpenoids. Its hydrolysis gives terpineol.
Biosynthetic conversion of geranyl pyrophosphate to the terpenes α-pinene and β-pinene (right) and to α-terpineol (bottom left).[11]
↑Yuasa, Yoshifumi; Yuasa, Yoko (2006). "A Practical Synthesis of d-α-Terpineol via Markovnikov Addition of d-Limonene Using Trifluoroacetic Acid". Organic Process Research & Development10 (6): 1231–1232. doi:10.1021/op068012d.
↑Davis, Edward M.; Croteau, Rodney (2000). "Cyclization enzymes in the biosynthesis of monoterpenes, sesquiterpenes, and diterpenes". Biosynthesis. 209. 53–95. doi:10.1007/3-540-48146-X_2. ISBN978-3-540-66573-1.
