Spearmint -carvone

Enantiomers can have striking differences however m properties that depend on the arrangement of atoms m space Take for example the enantiomeric forms of carvone (R) (—) Carvone is the principal component of spearmint oil Its enantiomer (5) (+) carvone is the principal component of caraway seed oil The two enantiomers do not smell the same each has its own characteristic odor... 

There are interesting examples of enantiomers that not only are found separately but also have different chemical properties when reacting with some reagent which is itself an enantiomer. For example (+ )-glucose is metabolized by animals and can be fermented by yeasts, but (—)-glucose has neither of these properties. The enantiomer ( + )-carvone smells of caraway whereas (—)-carvone smells of spearmint. 

Other synthetics with cost advantages and large volume productions are L-carvone [6485-40-17, the primary component in natural spearmint essence D-carvone [2244-16-8], the primary component in natural diU and caraway anethol [4180-23-8], in place of anise and fennel spices and smaller amounts of thymol [89-83-8] replacing thyme and disulfide synthetics for onion and gadic. AH of these synthetics must be labeled as artificial which may limit their use among consumers. 

Limonene (+15) is an important raw material for producing (-)-carvone [6485-40-1]. The process uses nitrosyl chloride and proceeds via nitrosochloride and oxime (78,79). The (-)-carvone (40) is found as the main component of spearmint oil and the (+)-carvone produced from (—)-limonene has the characteristic odor of diU. 

Examine actual three-dimensional structures for the twc enantiomers of carvone. One occurs naturally in carawa> while the other is found in spearmint oil, and are responsible for the characteristic odors of these materials. Determine which form, R or S, is responsible for which odor. 

Carvone, a substance responsible for the odor of spearmint, has the following structure. Tell how many hydrogens are bonded to each carbon, and give the molecular formula of carvone. 

Carvone is an unsaturated ketone responsible for the odor of spearmint. If car-vone has M+ = 150 in its mass spectrum and contains three double bonds and one ring, what is its molecular formula ... 

Carvone is the major constituent of spearmint oil. What products would you expect from reaction of carvone with the following reagents ... 

Numerous examples of the different biological effects of enantiomers are available. One of the enantiomers of limonene smells of lemons, the other of oranges one of carvone smells of caraway, the other of spearmint These differences obviously have important... 

Aldehydes occur naturally in essential oils and contribute to the flavors of fruits and the odors of plants. Benzaldehyde, C6H5CHO (8), contributes to the characteristic aroma of cherries and almonds. Cinnamaldehvde (9) is found in cinnamon, and vanilla extract contains vanillin (10), which is present in oil of vanilla. Ketones can also be fragrant. For example, carvone (Section 18.1) is the essential oil of spearmint. 

The main constituents of spearmint oil are /-carvone (Fig. 13.12.7) and /-limonene (Fig. 13.12.8). Oil of spearmint contains from 45 to 60% l-carvone, 6 to 20% of alcohols, and 4 to 20% of esters and terpenes, mainly /-limonene and cineole (see Fig. 13.12.4)J2J The optically isomeric form of carvone, d-carvone, is found in oil of caraway and oil of dill. Carvone appears to co-occur with limonene when present in a plant. 

The mammalian olfactory system possesses enormous discriminatory power. It is claimed that humans can perceive many thousands of different odorous molecules, termed odorants. Even slight alterations in the structure of an odorant can lead to profound changes in perceived odor quality. One commonly cited example is carvone, whose L- and D-stereoisomers are perceived as spearmint and caraway, respectively. However, more subtle molecular alterations can also generate striking changes in perception. 

At the cellular level, the various types of receptor, transporter, enzyme and ion charmel are all chiral in form. Thus although the enantiomers of a drug may have identical physicochemical properties, the way in which they may interact with chiral targets at the level of the cell will give rise to different pharmacod)mamic and pharmacokinetic properties. A few simple examples will illustrate how taste and olfactory receptors can differentiate between enantiomers. Thus R-carvone tastes like spearmint whereas the S-isomer tastes like caraway. Similarly, R-limolene smells like lemon whereas the S-enantiomer tastes of orange. 

The major constituent of caraway oil is (+)-carvone, and the typical caraway odour is mainly due to this component. On the other hand, the typical minty smell of spearmint oil is due to its major component, (—)-carvone. These enantiomers are unusual in having quite different smells, i.e. they interact with nasal receptors quite differently. The two enantiomeric forms are shown here in their half-chair conformations. 

Ravid U, Bassat M, Putievsky E, Weinstein V, Ikan R, Isolation and determination of optically pure carvone enantiomers from caraway Carum carvi L.), diU Anethum aveolens L.), spearmint Mentha spicata L.) and Mentha longifolia (L.) Huds, Flavour Fragr J 2 95-97, 1987. 

Ravid U, Putievsky E, Katzir I, Weinstein V, Ikan R, Chiral GC analysis of (5)(- -)- and (i )(—)-carvone with high enantiomeric purity in caraway, dill and spearmint oils. Flavour Fragr/7 289—292, 1992. 

Carvone is a chemical component of the spearmint plant that has been shown to enhance the growth and ability of Arthrobacter bacteria to degrade polychlorinated biphenyl (PCB). Until this discovery the only known method of strmnlating the bioremediation of PCBs was addition of biphenyl to the soil however, biphenyl is itself a toxic snbstance. 

Figure 2.1 Examples of chiral molecules where the enantiomers have different biological activity. ( -Carvone tastes of caraway while the (R)-enantiomer tastes of spearmint. The (S)-form of asparagine tastes...

Historically, terpenes have enjoyed a role as symptom-relieving therapeutics. Camphor and carvone (spearmint oil) have been used as soothing agents in the past history of pharmaceutical compounds. More recently, the role of terpenes in biochemistry has been more fully appreciated. P-Carotene, for example, may be cleaved into two units of vitamin A. Other terpenes, such as geraniol, are now recognized as pheromones (a chemical secreted by one individual of a given species in order to elicit a response in another individual of the same species). Pheromones are of interest in medicinal chemistry for a variety of indications for instance, attractant pheromones can be used for the control of insects known to spread human disease. 

Production. In the past, (+)- and (-)-carvones were isolated by fractional distillation of caraway oil and spearmint oil, respectively. However, these carvones are now prepared synthetically, the preferred starting material being (+)- and (-)-limonenes, which are converted into the corresponding optically active carvones. Since optical rotation is reversed in the process, (+)-limonene is the starting material for (—)-carvone. 

The compositions of Scotch and native spearmint oils differ as shown in Table 6 [486, 635-637a]. The main producer of spearmint oil is the United States, primarily the state of Washington. Smaller amounts are also produced in some Midwest states. Total annual production is about 1500t, 30 50% being of the native type and 50-70% of the Scotch type [637b]. Other minor cultivation areas for spearmint oils exist in China and India where oils with up to 80% carvone are produced [634b-634d]. 

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