Terpene alcohols, oxidation

L. L. (2013) A phthalate family oxygenase reductase supports terpene alcohol oxidation by CYP238A1 from Pseudomonas putida KT2440. Biotechnol Appl. Biochem., 60 (1), 9-17. 

An optically active, secondary terpene alcohol. ( —)-Piperilol is found in various eucalyptus oils and (-l-) piperitol in the oil from a species of Andropogon. A somewhat viscous oil of pleasant smell. It yields piperitone on oxidation with chromic acid. 

Modena and colleagues47 have developed use of some chiral, non-racemic terpene alcohols as directing groups for highly diastereoselective m-chloroperbenzoic oxidation of sulfides into sulfoxides. Specifically the isobornyl vinylic sulfides 8 undergo hydroxyl-directed oxidation to give a 9 1 ratio of diastereomeric sulfoxides (equation 11). 

Limonene is a liquid with lemon-like odor. It is a reactive compound oxidation often yields more than one product. Dehydrogenation leads to / -cymene. Limonene can be converted into cyclic terpene alcohols by hydrohalogenation, followed by hydrolysis. Nitrosyl chloride adds selectively to the endocyclic double bond this reaction is utilized in the manufacture of (—)-carvone from (+)-limonene (see p. 61). 

In addition to linalyl acetate, the oil contains linalool and other terpene alcohols, as well as their acetates. When the volatile components are evaporated, a distinct ambergris note develops that is attributed to oxidative degradation products of sclareol [515-03-7] [746-750a]. Sclareol is the main component in the concrete, obtained by solvent extraction of S. sclarea L. leaves [750b]. 

The monoterpenes are subdivided into three groups acyclic, monocyclic and bicyclic (there is only one tricyclic terpene tricyclene). Each group contains hydrocarbon terpenes, terpene alcohols, terpene aldehydes, ketones, oxides etc... 

The cycloaddition reaction of chiral thiocarbonyl 5-oxides derived from terpene alcohols such as (—)-menthol, ( —)-borneol, (+)-a-fenchol and (—)-3-tWo-hydroxy-2-CTitfo-phenylbornane affords 2-substituted 2-alkoxysulfonyl-3,6-dihydro-4,5-dimethyl-2//-thiopyran 1-oxides IIA and 11B as a mixture of diastereomers85. 

The hydrocarbons of the various groups which we have just discussed are the true terpenes. On oxidation these yield alcohol and aldehyde or ketone derivatives. The olefine terpenes, only, yield aldehydes that occur as constituents of natural products known as essential oils (p. 840). The derivatives of both groups of cyclic terpenes which are present in essential oils and plant gums and resins are either secondary alcohols or ketones. Among these latter are the camphors of which common camphor is the most important and best known example. In a general sense all of the oxidation products of the cyclic terpenes are termed camphors. 

Steam distillation is based on an aceotropic or carrier-gas distillation of two immiscible liquids. Due to the unfavourable ratio of vapour pressures and thus of mole fractions in the distillate, large amounts of water must be evaporated for the separation of small amounts of essential oils. This is connected to long distillation times at around 100°C and a considerable thermal stress leading to the formation of artefacts, oxidation and isomerisation to a certain extent. Moreover the water itself can be a reactant and hydrolyse terpene esters that make up the core of a flavour terpene alcohols remain partially dissolved in the water and thus are lost from the essential oil. All this can modify the essential oil composition and change the original typical flavour impression. 

CIC The basic Muscat note is produced from linalool, balanced with further terpene alcohols, geraniol and linalool oxides. The catty odour of the concord grape is based on methyl anthranilate, combined with ethyl-3-mercapto propionate, benzaldehyde adds the touch of a seedy character. 

Toxicology Irritating to eyes, skin TSCA listed Environmental Do not discharge into lakes, streams, ponds, or public waters Precaution Combustible incompat. with strong acids, strong bases, materials that react with terpene alcohols prolonged/excessive heat and/or exposure to air may cause decomp, or oxidation of the material Hazardous Decomp. Prods. CO, CO2, acrid fumes... 

Hazardous Decomp. Prods. Heated to decomp., emits toxic fumes of CO, CO2 emits toxic fumes underfire conditions NFPA Health 0, Reactivity 0 Storage Store in cool, dry place keep tightly closed keep away from oxidizing materials Uses Intermediate in mfg. of terpene alcohols fragrance in cosmetics Manuf./Distrib. Doingcom http //www.doingcom.com, Fluka http //www.sigma-aldrich. com... 

To date, only limited data are available on the enzymatic hydrolysis of trisubsti-tuted epoxides [611-613]. For example, a racemic allylic terpene alcohol containing a cii-trisubstituted epoxide moiety was hydrolyzed by whole cells of Helminthos-porium sativum to yield the (S,S)-diol with concomitant oxidation of the terminal alcoholic group (Scheme 2.94). The mirror image (/ ,S)-epoxide was not transformed. Both optically pure enantiomers were then chemically converted into a juvenile hormone [614]. 

The most widely occurring terpenes are the smallest molecules, that is, the monoterpenes, CioHjg, and their oxygenated derivatives such as ketones, aldehydes, alcohols, oxides, phenols, along with simple hydrocarbons. Their properties are determined by functional groups—oxygen-containing radicals attached to the carbon skeleton. 

Meesters, R. J. W., M. Duisken, and J. Hollender, 2007. Study on the cytochrome P450-mediated oxidative metabolism of the terpene alcohol linalool Indication of biological epoxidation. 37 ... 

FIGURE 19.22 Four stereoisomers of furanoid linalool oxides. (Modi ed from Noma, Y. et al.. Reduction of terpene aldehydes and epoxidation of terpene alcohols by S. ikutamanensis, Ya-2-1, Proceedings of 30th TEAC, 1986, pp. 204-206.)... 

Pine oil Mixing terpene alcohol and terpenes Acid value 1-2 CM3terpene alcohol 50-75 % CyMch terpene alcohol 50 60 % Oxidation product of dialkylphosphorodithioic acid 1-10 % solution... 

The position of these substances in the chromatogram is determined by the polarity of the parent compound. Menthofuran migrates just behind guaiazulene [182 a, 247]. The terpene and sesquiterpene epoxides follow, lying in the upper part of the ester zone on silica gel G layers (Table 23) (cf. also [155]). in agreement with El-Deeb [55]. The carbonyl and alcohol oxides follow with lower hRf-values. This sequence holds even at — 9° C using Freon (Frigen 21) as solvent [255]. 

PCC not only is selective for the oxidation of primary alcohols to aldehydes but also has little effect on carbon-carbon double bonds or other easily oxidized functional groups. In the following example, geraniol, a primary terpene alcohol, is oxidized to geranial without affecting either carbon-carbon double bond. 

The toxicity of terpene alcohols when used as fragrance ingredients has been intensively reviewed [77]. At concentrations likely to be encountered by consumers, these chemicals are considered nonirritating to human skin. At the present maximum use concentrations, their potential for eye irritation is considered minimal. 6,7-Dihydroxy geraniol is a potent skin sensitizer and has been prohibited in fragrance materials. Linalool may contain impurities or oxidation products that are strong sensitizers. Famesol is a weak sensitizer so that its use in fragrance materials has been restricted [77]. 

Two samples of papaya oil extracted from dried papaya seed harvested in Somalia yielded 25-26% of an orange-yellow colored liquid with a smell of cress. The composition of fatty acid was similar to other reported values. The relatively high polyphenol content (2.5% in seed oil) gives the seed oil excellent stability to oxidation. The phosphatides are low while the carotenoids are significant (lOmg/lOOg). Unlike the majority of vegetable oils, the terpenic alcohols constituted the most abundant fraction found in the unsaponifiable fraction (Strocchi et al., 1977). 

The most important reactions taking place on the hydroxy groups of alcohols are 0-H bond cleavage and C-O bond cleavage. With the O-H bond cleavage, reactions with strong acids proceed, as do oxidations of primary alcohols to aldehydes, secondary alcohols to ketones and reactions with organic acids (formation of esters). In foods the last three reactions are particularly important, and are usually enzymatically catalysed. Other important reactions are dehydration and the opposite reaction, hydration, which yield unsaturated hydrocarbons from alcohols and isomeric alcohols from unsaturated hydrocarbons, respectively. These reactions are particularly important in terpenic alcohols. In oleochemistry, oxidation and esterification reactions are used for the production of various lipid derivatives. 

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