Trans Anethole

The initial steps in the degradation of 2 -methyl-4-methoxystyrene (tran -anethole) by a strain of Arthrobacter aurescens are comparable to those already noted, except that the epoxide is hydrolyzed to a diol to produce 4-methoxybenzoate (Shimoni et al. 2002). 

For some of the reactions depicted in Scheme 14, copper(II) hexafluoroacetyl-acetonate [Cu(hfacac)2] proved to be a better catalyst than other chelates neither cyclopropanes nor allylic insertion products were found, and the yield of dihydrofuran was not affected by temperature in the range 70-132 °C 130). However, in phenylogous vinyl ethers such as 4-methoxystyrene or trans-anethole, cyclopropanes (58a, b) rather than dihydrofurans resulted 131>. 

Of conrse, the cyclic cation-radical formed should be less stable than the alkene cation-radical (which contains a double bond that is favorable for the spin-charge scattering). However, the cation-radical product and corresponding nentral species are generated in a concerted process. The process involves simultaneous covalent bond formation and one-electron reduction of the cyclic product (Karki et al. 1997). Similar to other branched-chain processes, the cation-radical dimerization is characterized by an activation enthalpy that is not too high. These magnitudes are below 20 kJ mol for the pair of cyclohexadiene and trani-anethole (p-MeOCgH4CH=CHCHMe, Z-form Lorenz and Bauld 1987). It is clear that the cation-radical variant of cyclodimerization differs in its admirable kinetic relief. For cyclohexadiene and tran -anethole, catalytic factors are 10 and 10, respectively (Bauld et al. 1987). 

A fraction of American sulfate turpentine oil (0.5% of the total) consists mainly of an azeotropic mixture of anethole and caryophyllene. trans-Anethole can be isolated from this mixture by crystallization. 

The main component of anise oil is trans-anethole, which is present at a concentration of 87-94% and which determines the melting point of the oil [263 266b]. 

Anethole is known to block the nuclear factor kappa B activation process [359] that is linked with cancer proliferation [272,360]. trans-Anethole was also found to inhibit the in vivo genotoxicity of xenobionts [345]. 

Anise oil trans-Anethol Alcoholic beverages, oral care... 

Star anise oil trans-Anethol Beverage and confectionery flavours... 

The development of mass spectrometric ionization methods at atmospheric pressures (API), such as the atmospheric pressure chemical ionization (APCI)99 and the electrospray ionization mass spectrometry (ESI-MS)100 has made it possible to study liquid-phase solutions by mass spectrometry. Electrospray ionization mass spectrometry coupled to a micro-reactor was used to investigate radical cation chain reaction is solution101. The tris (p-bromophenyl)aminium hexachloro antimonate mediated [2 + 2] cycloaddition of trans-anethole to give l,2-bis(4-methoxyphenyl)-3,4-dimethylcyclobutane was investigated and the transient intermediates 9 + and 10 + were detected and characterized directly in the reacting solution. However, steady state conditions are necessary for the detection of reactive intermediates and therefore it is crucial that the reaction must not be complete at the moment of electrospray ionization to be able to detect the intermediates. 

The case of anethole, depicted next, is interesting because of the relationship between the cation radical cyclodimerization and reduction processes. While the rapid cation radical dimerization of trans-anethole is strongly predominant, the cyclobutadimer formed is also ionized. Therefore, reductive cleavage of the dimer proceeds efficiently (80%) ... 

In the presence of catalytic amounts of tris(4-bromophenyl)ammoniumyl hexachloroanti-monate in methylene chloride at 0°C trans-anethole is smoothly converted in less than 5 min to the cyclobutane dimer (Bauld, Aplin, et al. 1996) (Scheme 6-12). 

In a comparative study on hydrodistillation and supercritical C02 (SC-COJ extraction of ground fennel seeds, the former possessed a less intense fennel seed aroma than extracts obtained by SC-C02 from organoleptic tests (Damjanovid et al., 2005). Optimal conditions of SC-C02 extraction (high percentage of trans-anethole, with significant content of fenchone and reduced content of methylchavicol and... 

The root essential oil contains (on average) a-pinene (1.0%), p-cymene (0.3%), /f-lenchyl-acetate (1.0%), trans-anethole (1.6%), eugenol (0.2%), myristicin (3%) and dillapiole (87%). On the other hand, the root and bulbous stem base of Florence fennel contains less than 1% of dillapiole but 70% of trans-anethole, giving a very different taste. The herbage contains 1.00—2.55% essential oil, up to 75% of which is trans-anethole. Anethole and fenchone... 

Many techniques are followed to identify and quantify the components of fennel essential oil. Krizman et al. (2006) developed a headspace-gas chromatography method for analysing the major volatile constituents in fennel fruits and leaves — a-pinene, a-phellandrene, limonene, fenchone, estragole and trans-anethole. 

Fennel oleoresin is prepared by solvent extraction of whole seeds and normally contains a volatile oil of 50% or a guaranteed content in the range of 52-58%. Only small quantities are produced for specific uses as it is not a substitute for fennel oil. Chemical analysis by Barazani et al. (2002) of the volatile fraction of oleoresins from fruits of seven natural populations of F. vulgare var. vulgare (bitter fennel) from the wild and after cultivation indicated the presence of two groups of populations. Chemotypic differentiation (relative contents of estragole and trans-anethole) or phenotypic plasticity increases within-species chemical variability, but the specific ecological roles of these essential oils remain to be uncovered. 

The essential oil, which ranges from 2.5 to 5.0%, includes the following chemical compounds tt-pinene, camphene, /i-pinene, linalool, cis-anethole, trans-anethole, safrole,... 

The GC-MS pattern of fruit volatile oil of star anise (7. vemm Hook) shows the presence of 25 components, which account for 99.9% of the total amount (Padmashree et al., 2007). The major components are trans-anethole (93.9%), estragole (1.05%) and limonene (1.05%) (Table 17.3). Fifteen components are identified from its acetone extract, accounting for 80.27% of the total amount. frans-Anethole (51.81%) is found as a major component, along with linoleic acid (11.6%), l-(4-methoxyphenyl)-prop-2-one (6.71%), foeniculin (5.29%) and palmitic acid (1.47%). 

Anethole FEMA No. 2086 trans-Anethole Isoestragole p-Propenylanisole 148.20/C10H12O/ ch3o—ch=chch3 colorless to faintly yel liq at or above 23° sweet taste/ anise ss—water m—chloroform, ether/ 234° 1 mL in 2 mL ale... 

Scheme 10. Mechanism of the aminium-salt induced cation radical cyclobutadimerization of trans-anethole.

Scheme 11. Syn/anti diastereoselectivity in the dimerization of tran -anethole.

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