Carvon

The optically active 1,4-cyclohexenediol monoacetate 525, prepared by hydrolysis of the me.so-diacetate with lipase, was converted into the optically pure cyclohexenone 526 by an elimination reaction in the presence of ammonium formate. Optically active carvone (527) was prepared from 526[343],... 

As a further application of the reaction, the conversion of an endocyclic double bond to an c.xo-methylene is possible[382]. The epoxidation of an cWo-alkene followed by diethylaluminum amide-mediated isomerization affords the allylic alcohol 583 with an exo double bond[383]. The hydroxy group is eliminated selectively by Pd-catalyzed hydrogenolysis after converting it into allylic formate, yielding the c.ro-methylene compound 584. The conversion of carvone (585) into l,3-disiloxy-4-methylenecyclohexane (586) is an example[382]. 

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... 

The difference m odor between (R) and (S) carvone results from their different behavior toward receptor sites m the nose It is believed that volatile molecules occupy only those odor receptors that have the proper shape to accommodate them Because the receptor sites are themselves chiral one enantiomer may fit one kind of receptor while the other enantiomer fits a different kind An analogy that can be drawn is to hands and gloves Your left hand and your right hand are enantiomers You can place your left hand into a left glove but not into a right one The receptor (the glove) can accommodate one enantiomer of a chiral object (your hand) but not the other... 

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. 

Human perception creates difficulty ia the characterization of flavor people often, if not always, perceive flavors differently due to both psychological and physiological factors. For example, certain aryl thiocarbamates, eg, phenylthiocarbamide, taste exceedingly bitter to some people and are almost tasteless to others (5). This difference is genetically determined, and the frequency of its occurrence differs from one population to another 40% of U.S. Caucasians are nontasters, whereas only 3% of the Korean population caimot perceive the strong bitter taste of the aryl thiocarbamates (6). Similar differences were found ia the sense of smell for compounds such as menthol, carvone, and ethyl butyrate (7). 

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. 

Caraway Seed. This spice is the dried ripe fmit of Carum carvi L. (UmbeUiferae). It is a biennial plant cultivated extensively in the Netherlands and Hungary, Denmark, Egypt, and North Africa. The seed is brown and hard, about 0.48 cm long, and is curved and tapered at the ends. It is perhaps the oldest condiment cultivated in Europe. The odor is pleasant and the flavor is aromatic, warm, and somewhat sharp (carvone). Caraway is used in dark bread, potatoes, sauerkraut, kuemmel Hqueurs, cheese, applesauce, and cookies. 

The oil possesses moderate antibacterial and strong antifungal properties. Thus the appHcation of the oil to the cmst of cheese could serve to prevent the formation of mycotoxia ia the cheese. The optical purity of the carvone ia caraway has been determined usiag a chiral gc column (72). It was found to be (i )(+) = 97.64% and (5 )(—) = 2.36%. 

Absorption, metaboHsm, and biological activities of organic compounds are influenced by molecular interactions with asymmetric biomolecules. These interactions, which involve hydrophobic, electrostatic, inductive, dipole—dipole, hydrogen bonding, van der Waals forces, steric hindrance, and inclusion complex formation give rise to enantioselective differentiation (1,2). Within a series of similar stmctures, substantial differences in biological effects, molecular mechanism of action, distribution, or metaboHc events may be observed. Eor example, (R)-carvone [6485-40-1] (1) has the odor of spearrnint whereas (5)-carvone [2244-16-8] (2) has the odor of caraway (3,4). 

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. 

A second method makes use of the lactone (31) from acetone dicarboxylate (40) and for which a synthesis from (—)-carvone has been reported (41). Displacement of chlorine from the 6-aminopenici11anic acid (6-APA) derived P-lactam (32) by (33) illustrates yet another approach to the dia2oketone (28) (42). 

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