Taste stereoisomers

FIGURE 1-23 Stereoisomers distinguishable by smell and taste in humans, (a) Two stereoisomers of carvone R) carvone (isolated from spearmint oil) has the characteristic fragrance of spearmint (S)-carvone (from caraway seed oil) smells like caraway, (b) Aspartame, the artificial sweetener sold under the trade name NutraSweet, is easily distinguishable by taste receptors from its bitter-tasting stereoisomer, although the two differ only in the configuration at one of the two chiral carbon atoms. 

A9-THC (2.1 in Fig. 2) is the only major psychoactive constituent of C. sativa. It is a pale yellow resinous oil and is sticky at room temperature. A9-THC is hpophihc and poorly soluble in water (3 p,g mL ), with a bitter taste but without smell. Furthermore it is sensitive to light and air [4]. Some more physical and chemical data on A9-THC are fisted in Table 1. Because of its two chiral centers at C-6a and C-lOa, four stereoisomers are known, but only (-)-trans-A9-THC is foimd in the Cannabis plant [5]. The absolute configuration of the... 

Products J 0 and J l are meaty in aroma and flavor. 1 possesses a characteristic meaty note reminiscent of 1iver-sausage whilst has a roasted meat odor and a burnt meat taste. In addition, the cis stereoisomer has a carrot-like and mushroom-like aroma and a herbaceous and tropical fruit note. The flavor thresholds in water of JJD and 1 1 are below 100 ppb. 

Just as positional isomers affect taste, so do different stereoisomers. There are eight amino acids that are practically tasteless. A group of three has varying tastes except for glutamic acid, these are probably derived from sulfur-containing decomposition prod-... 

Bassoli, A., Borgonovo, G., Busnelli, G., Morini, G., and Merlini, L. (2005). Monatin, its stereoisomers and derivatives, modeling the sweet taste chemoreception mechanism. Eur. J. Org. Chem. 2005, 2518-2525. 

The sensory test of the four isomers revealed that 56 was 1100-1200 times as sweet as sucrose. Other three stereoisomers were all bitter and somewhat pungent with no perceptible sweet taste. The naturally occurring (6S, l,5 )-(+)-hernandulcin (56) was the only stereoisomer with sweet taste. 

White crystalline solid bitter in taste melts at 177°C (350.6°F) pH of satnrated aqueous solution 8.8 prodnces bine finorescence slightly solnble in water (0.05 g/100 mL) at 20°C (68°F), dissolves readily in alcohols and chloroform. Qninine forms three stereoisomers epiqninine, qninidine, and epiqninidine. 

T. Yamazaki, Y.-F. Zhu, A. ProbstI, R. K. Chadha, and M. Goodman, J. Org. Chem., 56, 6644 (1991). Probing a Molecular Model of Taste Utilizing Peptidomimetic Stereoisomers of 2-Aminocyclopentanecarboxylic Acid Methyl Ester. 

Organoleptic Properties. Stereochemical differences of enantiomeric excipients may influence perception by sensory organs. Kutti [17] reported as early as 1886 that the interaction of stereoisomer with chiral receptors led to chiral discrimination as a consequence of the formation of diastereomers. He observed that the dextrorotatory asparagine has a sweet taste whereas the levorotatory form is tasteless. Greenstein and Winitz [18] and Solms et al. [19] reported such differences for many amino acids. Shallenberger et al. [20] reported that for some monosaccharides, both isomers have similar sweetness. In contrast, aspartame (A-aspartylalanine methyl ester) is marketed as the l,l isomer because it is more than 100 times as sweet as sucrose. However, the l,d diastereomer of aspartame is bitter [11], It should be noted that the individual differences of perception of these properties could vary. 

Among the tricyclic aromadendrols viridiflorol (202), which occurs, for instance, in peppermint oil from Piedmont Mentha piperita L. Italo-Mitcham), is supposed to confer to this essential oil its characteristic note. When added to normal peppermint oils, (202) enhances their sweetish scent without modifying their taste and aroma 415). A dia-stereoisomer of (202), globulol, is present in eucalyptus oil, and is described as odorless 204). Maaliol (203), an alcohol which was first isolated from maali resin 62), was found in fresh roots of Valeriana officinalis L. (595) and also in the Indian variety Valeriana Wallichii D.C. 416). Maaliol-containing oils from Valeriana Wallichii D.C. are said to have a finer odor 582). In addition, maalioxide (204) 62) was found in the same oil 416 presumably as an artifact of alcohol (203). The cyclic ether is characterized by its fine woody odor quality 443). 

A. crystallizes in colorless and odorless platelets, which are easily soluble in water or ethanol. It possesses a strong acidic taste and a high reducing power (di-enolic constitution). Aqueous solutions are rapidly oxidized by air. From 4 possible stereoisomers (- isomerization), only the L-threo configuration has vitamin C potency. 

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