Limonene epoxidation

Santa, A.M., Vergara, J.C., Palado, L.A., and Echavarria, A. (2008) limonene epoxidation by molecular sieves zincophosphates and zincochromates. Catal. Today, 133-135, 80-85. 

Analysis of Spray Dried Samples. Moisture content was determined in duplicate via toluene distillation and total volatile oil by Clevenger (l ). Surface oil was measured by Soxhlet extraction (2). Shelf-life was determined by gas chromatography (6) the end of shelf-life was the time taken (at 37 C storage) to reach a limonene epoxide concentration of 2 mg/g oil. 

Fig. 4. Shelf-life of orange oils (as measured by limonene epoxide formation) as influenced by flavor carrier. (Reproduced with permission from ref. 46. Copyright 1986 Institute of Food Technology.)...

The two limonene epoxides (93) behave differently when treated with lithium in ethylamine. The trans-epoxide (93a) yields exclusively trons-) -terpineol (94a), excess lithium and long reaction periods reducing the double bond, whereas the c/s-epoxide (93b) yields not only cis-)8-terpineol (94b), but also neo- (95) and isodihydrocarveol (96). The menth-l-ene epoxides [e.g. (97)] behave similarly. ... 

In the same context, it was shown that this fungus was also capable of achieving the diastereoselective hydrolysis of the exocyclic limonene epoxides, thus opening the way to the synthesis of either enantiopure bisabolol stereoisomer [174]. One of these enantiomers, i. e. (4S,8S)-a-bisabolol, is used on an industrial scale for the preparation of various skin-care creams, lotions and ointments. 

R. Barrera Zapata, A. L. Villa, C. Montes de Correa, Limonene epoxidation Diffusion and reaction over PW-amberlite in a triphasic system, Ind. Eng. Chem. Res. 45 (2006) 4589. 

Computational approaches to evaluate different mechanistic proposals for an enzyme have made great strides in the past 10 years. The chapter by Hopmann and Himo describe one such approach and its application to three different enzymatic reactions involving the transformation of an epoxide. The procedures and parameters to make a model of the active site are presented first and are followed by discussions of limonene epoxide hydrolase, soluble epoxide hydrolases, and haloalcohol dehalogenase. The results generally support the currently accepted mechanism for each enzyme but provide new insights into their regioselectivities. 

In this chapter, we will provide an overview of the employed methodology. To illustrate the various aspects of the methodology and to give the reader a feeling about the state of the art of the field, three very recent applications will be discussed in detail. All three enzymes are concerned with epoxide-transforming reactions, namely limonene epoxide hydrolase (LEH), soluble epoxide hydrolase (sEH), " and haloalcohol dehalo-genase C (HheC). First, however, a brief presentation of DFT and its accuracy will be given. 

LEH limonene epoxide hydrolase from Rhodococcus erythropolis DCL14 Leu leucine... 

The previously unknown (+ )-(lS,2S,4R)-isodihydrocarveol (157) has been made from (+ )-limonene epoxide (158) as a component of a mixture of isomers, either with lithium in ethylamine or with the stoicheiometric amount of lithium aluminium hydride. Dihydrocarveol (159) has been synthesized from 4-acetyl-1-methylcyclohexene by conventional means.A method that is said to convert allyl alcohols into the corresponding chlorides without allyl rearrangement has been applied to carveol. The chloride was indeed obtained, but since the rotations of the compounds were not recorded it is unfortunately impossible to draw any conclusions about rearrangement. An ingenious synthesis of pure stereoisomers of carvomenthone-9-carboxylic acids involves a [2 -I- 2]-type cycloaddition of an ynamine to 2-methylcyclohex-5-enone (160). This leads... 

FIGURE 19.41 Enantioselective biotransformation of (45)-(69a ) and (4i )-limonene epoxides (69a) by cyanobacterium. (Modi ed from Hamada, H. et al., Enantioselective biotransformation of monoterpenes by Cyanobacterium, Proceedings of 47th TEAC, 2003, pp. 162-163.)... 

Gyanchandani [85] has thus chromatographed caraway seed oil and dill oil under standard conditions and determined the position of the limonene epoxide (1,2) which had been formed by autoxidation of limonene. Nigam, Sahasrabudhe and Levi [185] have detected piperitone oxide in peppermint oils in a similar way. Attention has been drawn repeatedly to the bisabolene oxides I, II and III along with chamazulene in the assessment of camomile oils [78, 224, 305, 306]. 

Limonene also has an effect on the central nervous system. Further studies have shown the relaxant properties and anxiolytic effect of EO of Citrus sinensis, suggesting a possible depressant activity of these constituents [21]. De Almeida et al. [22] analyzed the effects of (-t)-limonene epoxide on the CNS of male Swiss mice. 

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