Raspberry ketone

While a large number of volatile compounds contribute to the flavor of raspberries, most are present at less than 10 ppm. 

Compounds include alcohols, acids, esters, carbonyls, ketones, and other hydrocarbons. However, a particular ketone l-(4-hydroxy phenyl)-3-butanone has an odor very much like raspberry [7,30]. This particiilar ketone, i.e., raspberry ketone, is sold under trade names Frambinon (Dragoco) and Oxyphe-nylon (IFF). In Hawai, the acetate of raspberry ketone is used under the trade name of Cue-Lure CAS No. [3572-06-3] to attract the harmhil melon-fly, Dacus Curcurbitae. 

It may not be out of place to mention that ketones are partly or wholly responsible for the odor of many natural products such as camphor, raspberries, coffee, musk, caraway, butter, rue, and jasmine. 

The study of the structures of these odoriferous ketones has enabled organic chemists to prepare new and useful compounds for food and drink additives. 

Raspberry ketone is very slightly soluble in water, but it is soluble in ethyl alcohol, propylene glycol 

This flavor ingredient is available on the market essentially only of synthetic origin, and it is employed in soft drinks, sweets, puddings, and ice creams. The interest in its biotechnological production has been quite high, mostly because of its low concentration in natural sources and the impracticality of the extraction processes. 

Several candidate genes from raspberry and other plants involved in the biosynthesis have been recently cloned and expressed in E. coli. Cultures of the resulting recombinant strain produced significant levels of raspberry ketone (up to 5 mgl ), but the yields could not be improved [146]. 

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Hydroxybenzaldehyde has an agreeable aromatic odor, but is not itself a fragrance. It is, however, a useful intermediate in the synthesis of fragrances. The methyl ether of -hydroxybenzaldehyde, ie, -anisaldehyde, is a commercially important fragrance. Anisaldehyde can be made in a simple one-step synthesis from hydroxybenzaldehyde and methyl chloride. Another important fragrance, 4-(p-hydroxyphenyl)butanone, commonly referred to as raspberry ketone, can be prepared from the reaction of -hydroxybenzaldehyde and acetone, followed by reduction (see Flavors and spices). 

Donzelli, F., Fuganti, C., Mendozza, M., Pedrocchi-Fantoni, G., Servi, S. and Zucchi, G., On the stereochemistry of the Baeyer-Villiger degradation of arylalkylketones structurally related to raspberry ketone by Beauveria bassiana. Tetrahedron Asymm., 1996, 7, 3129-3134. 

Redundancy analysis was able to explain 47% of total variance in flavour in relation to the 62 aroma compounds in the flrst two components PLS explained only 36%. Neither method, however, correlated either raspberry ketone or linalool with important aroma notes, suggesting concentrations of flie im ct compounds are not important in determining varietal character. 

Raspberry ketone is prepared by alkali-catalyzed condensation of the alkali salt of 4-hydroxybenzaldehyde and acetone, followed by selective hydrogenation of the double bond in the resulting 4-hydroxybenzalacetone. Other syntheses start from phenol which is converted into 4-(4-hydroxyphenyl)-2-butanone with methyl vinyl ketone (e.g., in the presence of phosphoric acid) [179] or with 4-hydroxy-2-butanone in the presence of concentrated sulfuric acid [180]. 

Approximately 230 volatile compounds have been identified in raspberry fruit [35]. The aroma of raspberries is composed of a mixture of ketones and aldehydes (27%) and terpenoids (30%), alcohols (23%), esters (13%) and furanones (5%). The raspberry ketone (Fig. 7.5) along with a-ionone and jS-ionone have been found to be the primary character-impact compounds in raspberries. Other compounds such as benzyl alcohol, (Z)-3-hexen-l-ol, acetic acid, linalool, geraniol, a-pinene, jS-pinene, a-phellandrene, jS-phellandrene and jS-caryophyllene contribute to the overall aroma of mature red raspberries [101-105]. The most important character-impact compounds of raspberries are summarised in Table 7.3. 

Raspberry ketone [4-(4 -hydroxyphenyl)-butan-2-one], the impact compound found in raspberries, can be obtained by enzymatic reactions The first step is the /i-glucosidase-catalysed hydrolysis of the naturally occurring betu-loside to betuligenol. The latter can be transformed into raspberry ketone by microbial alcohol dehydrogenase (Scheme 22.2) [56]. 

Scheme 22.2 Enzymatic production of raspberry ketone from betuloside [56]...

Scheme 23.7 Biotechnological strategies for the production of natural raspberry ketone...

Methyl eugenol 013,4-dimethoxy-l-allylbenzene [95-15-2] was fust characterized in 1915 as a powerful attractant for the male oriental fruit fly, Dams dorsalis, and attracts at least 60 other closely related Dams spp. Raspberry ketone [5471-51-2] or l-(4-/>-hydroxyphenyl)-2-butanone [5471-51-2] (174) is an equally powerful attractant for the melon fly, Dams mmrbitae, and the Queensland fmit fly, D. tryoni, and at least 180 other closely related Dams spp. The acetyl ester (cue-lure) (175) is more volatile and is a synthetic parakairomone especially effective for monitoring infestations by these species. Methyl eugenol and cue-lure [3572-06-3] have been used successfully in "male annihilation" of the oriental fmit fly and the melon fly by applying them to fiber board blocks or pieces of twine together with malathion or naled insecticides and distributing them over infested areas at doses of 15 g of attractant and 1 g of the insecticide per ha. 

K. Grob and J. M. Stoll, Loop-type interface for concurrent solvent evaporation in coupled HPLC-GC. Analysis of raspberry ketone in a raspberry sauce as an example , J. High Resolut. Chromatogr. Chromatogr. Commun. 9 518 -523 (1986). 

When the parent phenol complex of [Os] 85 is combined with MVK and pyridine in acetonitrile, a Michael addition occurs to give the 4H-phenol complex 86 in 91 % yield (Scheme 11). This complex is remarkably stable and resists rearomatization even when allowed to stand in an acidic solution of acetonitrile for 24 h. However, addition of an amine base induces rearomatization to yield complex 87. This complex may be heated to afford the deme-talated substitution product 88 (raspberry ketone) in 71 % yield (based on 85) [29]. 

Aldehydes can be formed by oxidizing alcohols-—in fact the liver detoxifies ethanol in the bloodstream by oxidizing it first to acetaldehyde (ethanal, CH3CHO). Acetaldehyde in the blood is the cause of hangovers. Aldehydes often have pleasant smells—2-methylundecanal is a key component of the fragrance of Chanel No 5 , and raspberry ketone is the major component of the flavour and smell of raspberries. 

The two ketones are all flavour compounds too. The first, (-)-carvone, is the chief component (70%) of spearmintoil. Carvone is an interesting compound in Chapter 16 you will meet mirror-image isomers known as enantiomers, and (-)-carvone s mirror image (+)-carvone, is the chief component (35%) of dill oil. Our taste can tell the difference, though an NMR machine can t and both carvones have identical NMR spectra. See Chapter 16 for more detailf The second ketone is raspberry ketone and is largely responsible for the flavour of... 

It should not surprise you that regioselective reduction of the C=C double bond alone is best done using catalytic hydrogenation as the C=C bond is weaker than the C=0 bond. The flavouring compound known as raspberry ketone is made by this method. 

Tateiwa, J. I., H. Horiuchi, K. Hashimoto, and T. Kamauchi. 1994a. Cation-exchanged montmorillonite-catalyzed facile Friedel-Crafts alkylation of hydroxy and methoxy aromatics with 4-hydroxybutan-2-one to produce raspberry ketone and some pharmaceutically active compounds. J. Org. Chem. 59 5901-5904. 

A variety of benzene-derivatives are found in many grape varieties, including vinyl phenols, benzyl alcohol, 2-phenyl ethanol and raspberry ketone. Vinyl phenols are characterised by spice and dove-like, 2-phenyl ethanol by rose and lilac, and raspberry ketone by a raspberry attribute (Francis and Newton 2005). It should be noted that, although a portion of 2-phenyl ethanol can derive from glycoside hydrolysis, a greater proportion of this compound is formed in the metabolism of the amino acid phenylalanine (Ugliano et al. 2006). 

SYNS ANISYLACETONE 2-BUTANONE, 4-(p-METHOXYPHENYL)-(6CI,7CI,8CI) ENT 20,279 FEMA No, 2672 4-METHOXYBENZYLACETONE p-METHOXYPHENYLBUTANONE 4-(p-METHOXY-PHENYL)-2-BUTANONE RASPBERRY KETONE METHYL ETHER... 

While essential oils and natural extracts, which are obtained from natural resources by various processes, mainly constitute complex mixtures, aroma chemicals are uniform compounds, which can be both of natural or synthetic origin. A number of representatives of frequently used aroma chemicals show an enormous discrepancy between synthetic and natural material. Raspberry ketone shall be used as an example here for the year 1992, an estimated yearly worldwide consumption of 400 kg of natural material is countered by the 300-fold amount of synthetic material which found industrial usage [8]. 

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