Flavour esters, synthesis

Ma F, Hanna MA (1999) Biodiesel production a review. Biores Technol 70 1-15 Magnusson A, Hull K, Holmquists M (2001) Creation of an enantioselective hydrolase by engineered substrate-assisted catalysis. J Am Chem Soc 123 4354 355 Manjon A, Iborra JL, Arocas A (1991) Short-chain flavour ester synthesis by immobilized lipase in organic media. Biotechnol Lett 13 339-345 Margolin A (1996) Novel crystalline catalysts. TIBTECH 14 223-230... 

Dheeman DS, Henehan GTM, Frias JM (2011) Purification and properties of Amycolatopsis mediterranei DSM 43304 lipase and its potential in flavour ester synthesis. Bioresour Technol 102 3373-3379 Dive V, Yiotakis A, Nicolaou A, Toma F (1990) Inhibition of Clostridium histolyticum collagenases by phosphonamide peptide inhibitors. Eur J Biochem 191 685-693... 

Rhizopus arrhizus dead mycelium was found to be very active in organic solvents as a naturally immobilized lipase. Triglycerides hydrolysis and interesterification, esters and glycerides synthesis, natural flavour esters preparation and racemic mixtures resolution in pharmaceutical drugs synthesis are among the successfully designed processes, each of one with a specific reactional medium. 

A typical research example includes the synthesis of a K -channel blocker intermediate (Fig. 7.10). Here, an aminotransferase is used to replace a keto group by an amino function to yield the desired intermediate [20]. Other potential applications include the biosynthesis of flavouring esters. In nature such compoimds are often formed by a specific acyl CoA transferase. For practical purposes, however, the alternative, less complicated route, using lipases and esterases in their synthetic mode, seems more appropriate. 

C. Preston, E. Richling, K. Kahle, M. Kraus, W. Hummer, M. Appel, F. Heckel, P. Schreier (2005) Ester synthesis authenticity assessment by stable isotope analysis. In T. Hofmann, M. Rothe, P. Schieberle (eds.) State-of-the-Art in Flavour Chemistry and Biology. DFA, Garching, pp. 358-362... 

A.P. de los Rfos, F.J. Hernandez, F. Tomas-Alonso et al.. Synthesis of flavour esters using free Candida antarctica lipase B in ionic hquids, Elavour Eragrance J. 23 (2008) 319-322. 

The most important and frequently used terpene esters in flavours are the acetates of nerol, geraniol, citronellol, linalool and isoborneol [12], As discussed before, all these terpene alcohols are available both from renewable resources and from petrochemical origin. Acetic acid can be obtained from renewable resources by pyrolysis of wood as wood vinegar, and also by synthesis from petrochemical origin. 

Lipases play an important role in organic synthesis and also in flavour biotechnology. Pig pancreatic extract and especially many microbial lipases are used for ester hydrolysis, esterification (alcohol and acid), transesterification (ester and... 

The work from Sheldon s group [10] was the first to present the use of ionic liquids in the enzymatic synthesis of esters. Since then, there have been many reports on biosynthesis of esters in ionic liquids. De los Rios et al. [64,65] synthesised a wide range of aliphatic organic esters, commonly used in the perfumery, flavour and pharmaceutical industries, by transesteriflcation from vinyl esters and alcohols catalysed by free CaLB in different 1,3-dialkylimidazolium-based ILs (Fig. 7.2). They analysed the effects of the alkyl chain lengths of the acyl donor and the alcohol. The optimum (C6 for acyl donor and C4 for alcohol) chain lengths were found because the activity decreased with further increase in alkyl chain length. The authors attributed the enzyme behaviour to a substrate modulation mainly due to the different affinity of the lipase towards the different substrates and steric hindrance and denaturalisation by small alcohol molecules. 

Synthesis of organic esters, which are used as perfumes, flavours, pharmaceuticals, plasticisers, solvents and intermediates, by esterification can be performed using either mineral acids or solid acid catalysts... 

Constituents of Bartlett Pears.— The synthesis of ethyl and methyl E-2,Z-6-dodecadienoates, two constituents of Bartlett pears, has been described these esters have proved essential to the reconstruction of good pear flavour. 

Metal-catalysed ring-opening reactions of lactones can be useful in synthesis. For example, a one-pot procedure for the formation of (Z)-4-alkenoic acids, the esters of which are components of various perfumes and flavours, relies on the cis nature of addition of dialkylcuprates to acetylenes to afford (Z)-alkenyl-cuprates. These cuprates induce ring opening of -propiolactone in a regioselec-tive manner by alkyl oxygen fission to give the desired compounds in excellent yield. ... 

The five-carbon short-chain isovaleric acid is apphed for the production of flavours and perfumes. Also, this acid is broadly used as intermediate for synthesis of insecticides, fungicides and depressants. The esters serve as plasticisers (Rdmpp 2005). 

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