Nature esters

Terpinyl Acetate.—The acetic acid ester of terpipeol is also a natural ester. It nas a refreshing odour, and is often described as being a bergamot and lavender substitute. The writer, however, considers this description unjustifiable, and that it is really due to the fact that it is so often used and recommended as an adulterant for these two essential oils. Terpinyl acetate isia colourless oil, of the formula... 

The natural esters present in essential oils are usually those of acetic, butyric, and valerianic acids, and in the case of geranium oil, tiglate acid. 

Pyrethrolone and cinerolone make up the keto alcohol moiety of the pyrethrins. Both of these keto alcohols have one asymmetric carbon at the 4-position and a double bond in the side chain which is capable of cis-trans isomerism in the 2-position. It is possible, therefore, to have four stereoisomers for each keto alcohol. Katsuda et al. (22) show that only the ( + ) form occurs in the natural esters. Elliott (8) has shown recently, by a new procedure developed to obtain pure ( + ) pyrethrolone, that the hitherto unidentified prye-throlone C is in reality pyrethrolone contaminated with thermally isomerized material. (+) Pyrethrolone forms a crystalline monohydrate from which the pure alcohol is obtained. The natural configurations of the keto alcohols in the esters are insecticidally more active, as is the case with the acid moiety. 

The GALDI-MS measurements covered a selection of natural ester waxes, both from animal (beeswax, shellac wax, spermaceti) and vegetable sources (candelilla, cane, carnauba, cotton fibre, esparto, ouricouri). Generally, the waxes were readily distinguishable by their characteristic distribution of molecular masses. In some cases, markers could be identified on the basis of literature data. 

Hydroxide ions react to split ( hydrolyse ) natural esters in the skin to form glycerol (II) and palmitic or stearic acid - a reaction called saponification. Palmitic and stearic acids subsequently react with the base to form the respective long-chain carboxylate anions - which is soap. 

What are the advantages and disadvantages of using synthetic esters in consumer products as compared to using natural esters ... 

When utilization tests were run on a group of 18 male and 7 female human subjects, wide variations in blood level responses were found, particularly among the males.36 [Both in animals (rats) and humans the two sexes respond somewhat differently.] When 134,000 ig. of vitamin A in four different forms, viz., vitamin A alcohol, vitamin A acetate, vitamin A natural ester No. 1, and vitamin A natural ester No. 2, was fed to the group of 18 males on four different occasions, the serum levels found after 6 hours ranged from 178 to 1423 ig. per 100 ml., 122 to 1170 ig. per 100 ml., 110 to 1183 ig. per 100 ml., and 114 to 1230 ig. per 100 ml., respectively. These nearly 10-fold variations in serum levels do not, of course, indicate 10-fold variation in need, but they do show that the vitamin when given in relatively large doses does behave very differently in different individuals. 

Many of the fragrances and tastes from plants are due to esters. The smells we perceive are generally due to a combination of esters, but often one ester fragrance will dominant. By mimicking these natural esters, the food industry has synthesized hundreds of different flavoring agents. Three of these are shown in Figure 15.14. Many pheromones are esters. Pheromones are chemical compounds used by animals for communication. Many medications are also esters. Aspirin is an ester of salicylic acid (see Chapter 13). 

Esters are usually prepared by esterification of carboxylic acids with alcohols. Industrial procedures depend on the physical properties of the esters concerned. Biosynthetic methods may be applied to produce natural esters for flavor purposes [24]. 

Natural esters are widely used by the aroma and fragrance industries because of their fruity or floral taste/odor. Many of them are alkyl esters of formic, acetic, propionic, and butyric acids. The development of an efficient biotechnological process, compatible with the natural label for the products but offering costs comparable to the costs of chemical processes, has been achieved, representing the first application of gas/solid technology on an industrial scale [51]. 

Figu re .8 Schematic diagram of an industrial continuous solid/gas bioreactor developed for the production of natural esters in a closed nitrogen loop. 

The production of natural esters is the first example of a large-scale application of solid/gas biocatalysis, and many other systems are being studied today with a view to short or medium term development. 

Esters obtained from alcohols and fatty acids have many remarkable applications. Those from long chain acids (12-20 carbon atoms) and short chain alcohols (3-8 carbon atoms) have been widely employed in the food, cosmetic, and pharmaceutical industries (1). Natural esters such as those from jojoba oil, carnauba wax, and whale oil have been used. However, these oils are expensive and are not usually available in large amounts. Therefore, it is desirable to develop methods for the production of such esters using cheaper and more plentiful raw materials (2). 

In general, acid chlorides and acid anhydrides are too reactive to occur naturally, and nitriles are rare in nature. Esters and amides, on the other hand, are very common. Many esters have pleasant odors, often sweet or fruity, and are responsible for the fragrant odors of fruits and flowers. They are components of many flavorings, both natural and artificial. For example, isopentyl acetate has a strong banana odor, and methyl bu-tanoate is used as an artificial rum flavoring. Typical fats are triesters formed from long-chain fatty acids and the triol glycerol. 

Like many other lipids with free hydroxyl groups, tocopherols and tocotrienols can form natural esters with molecules that contain a carboxylic acid group (Panfili et al., 2003 Wang et al., 1998). Although... 

Nature Ester of Natural Oils Appearance Liquid % Act. 100 Ionic Type Nonionic... 

To avoid any possible a — 7 conversion promoted by the anhydrous conditions during esterification Franzblau (1962) and Franzblau el al. (1963) developed a method by which the hydroxamic acids could be formed directly from the unmodified proteins in an aqueous system. This was achieved using a water-soluble carbodiimide, 1-cyclohexyl-3[2-morpholinyl-(4)-ethyl]-carbodiimide metho-p-toluene sulfonate (Fig. 5). The reaction conditions (pH 4, 25°C, in aqueous medium) eliminated any possibility of a —> 8 conversion. These conditions also precduded the possibility of hydroxyaminolysis of the natural ester linkages of collagen which will be discussed in Section V. This method, in common with all the others used to study 7-glutamyl links, was not quantitative. After subsecpient dini-... 

S. Asadauskas, Oxidative Degradation of Fluids Based on Synthetic and Natural Esters, PhD Thesis, Pennsylvania State University, State College, Pennsylvania, 1997, pp. 88-97. 

Fats are natural esters of propane-1,2,3-triol (glycerol). Soap used to be made by boiling animal fats with alkali this is why the hydrolysis of esters used to be called saponification . 

Amylopectin of potato starch and probably amylopectin of other tuber starches occurs as a natural ester of phosphoric acid. Potato amylopectin" contains approximately 0.07-0.09% phosphorus, " or one phosphate group for every 212 to 273 anhydroglucose units. The phosphate appears to be attached mainly to the primary alcohol group since, on hydrolysis, potato amylopectin (separated by electrodialysis)... 

Vesely and Jakes (13) pointed out that the definition for lipides adopted in 1923 was not sufficiently precise. It included, among lipides, the fats formed of mixtures of esters and nonlipidic substances (free fatty acids, steroids, carotenoids, hydrocarbons) on the other hand, certain essential oils formed mainly of esters might be considered lipides. Vesely and Jakes advocated a more precise and concise definition for lipides natural esters nonvolatile with steam and possessing no aromatic ring in their molecule. ... 

Fermentation derived natural carboxylic acids are important to the flavor industry for use in dairy and sweet flavors and as substrates for the production of natural esters. A process has been developed for the production of butyric acid which utilizes the anaerobic conversion of dextrose to butyric acid by the bacterium... 

Caserns have natural ester-bound phosphate and this gives caseins some of their unique properties. Whey proteins do not naturally contain phosphate ester groups. Studies have shown that the phosphorylation of caseins and whey proteins creates novel functionality in these proteins. 

Presently, there is a strong demand for environmentally acceptable fluids. As biolubes , they need to satisfy biodegradation and bioaccumulation standards, which mineral oil-based fluids cannot achieve. Therefore, the use of synthetic and natural esters for many industrial applications will develop [119]. Not only the base fluids but also the antioxidants used in them will have to fulfil certain specifications for aquatic toxicity, biodegradation and bioaccumulation. Because the antioxidant response of these new fluids is different from mineral oil-based lubricants, new classes of ashless bio-antioxidants may need to be developed. 

A series of diesters of retronecine (64), and some acyl derivatives of indicine, monocrotaline (55), and retrorsine have been prepared for toxicological comparison with the natural ester alkaloids. " ... 

Following this exploratory work, the Schmidt group (13) reported the first homochiral synthesis of methyl (-)- and (+)-nonactate using (S)-propylene oxide as the only enantiomerically pure starting material (Scheme 4). This gave the mixture of diastereoisomeric methyl nonactates 38, 39,40 and 41, all with the ( -configuration at C-8, and chromatographic separation provided 25% of the natural (-) ester 38. The mixture of the other three diastereoisomers (39+40+41) was converted by Walden inversion into a mixture of the same three compounds with C-8 inverted, from which (+)-methyl (25,35,6R,8/J)-nonactate 44 could be isolated in approximately the same amount as its enantiomer 38. 

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