Lipase-catalysed

Lipases catalyse reactions at interfaces, and to obtain a high rate of interesterification the reaction systems should have a large area of interface between the water immiscible reactant phase and the more hydrophilic phase which contains the lipase. This can be achieved by supporting the lipase on the surface of macroporous particles. 

Fig. 5.13. Lipase-catalysed hydrolysis of racemic ibuprofen ester. CRL Candida rugosa lipase.

Searching for a method of synthesis of enantiopure lamivudine 1, the compound having a monothioacetal stereogenic centre, Rayner et al. investigated a lipase-catalysed hydrolysis of various racemic a-acetoxysulfides 2. They found out that the reaction was both chemoselective (only the acetate group was hydrolysed with no detectable hydrolysis of the other ester moieties) and stereoselective. As a result of the kinetic resolution, enantiomerically enriched unreacted starting compounds were obtained. However, the hydrolysis products 3 were lost due to decomposition." In this way, the product yields could not exceed 50% (Equation 1). The product 2 (R = CH2CH(OEt)2) was finally transformed into lamivudine 1 and its 4-epimer. ... 

Finally, prochiral bis(hydroxymethyl)phenylphosphine oxide 82 was desym-metrisized using either a lipase-catalysed acetylation (Method A) or hydrolysis of the corresponding diacetyl derivative 83 (Method B), to give the chiral monoacetate 84. Application of the two reverse procedures made it possible to obtain both enantiomerically enriched forms of 84 (Equation 40). ... 

The role of reversed micelles in the manufacture of fine chemicals with enzymes also needs to be assessed and analysed. An outstanding example is lipase catalysed interesterification to produce cocoa butter substitute from readily available cheap materials (Luisi, 1985). This example of reversed micelles is sometimes referred to as a colloidal solution of water in organic systems. A number of water insoluble alkaloids, prostanoids, and steroids have been subjected to useful transformations (Martinek et al., 1987). Peptide synthesis has also been conducted. The advantages of two liquid phases are retained to a very great extent the amount of water can be manipulated to gain advantages from an equilibrium viewpoint. 

Continuous lipase catalysed esterification of oleic acid... 

In addition to Rh-catalysed hydroformylation, this special phase behaviour has been successfully applied to other continuous catalytic reactions - such as Ni-catalysed, enantioselective hydrovinylation [66] and the lipase-catalysed kinetic resolution and enantiomer separation of chiral alcohols [67]. 

The lipase-catalysed resolution of racemic 105 in the presence of vinyl acetate afforded isoxazolidines 105 and their corresponding acetates in 52-82% ee. A higher optical purity... 

A second-generation manufacturing process involving a highly enantio- and diastereo-selective lipase-catalysed kinetic resolution step has recently been reported for the production of pregabalin, a lipophilic y-aminobutyric acid analogue that was developed for the treatment of several central nervous system disorders (Scheme 1.32). ° ... 

Other examples of efficient enzymatic resolutions by reaction at a remote position from stereocentres have been reported, such as the lipase-catalysed resolution of a synthetic intermediate of escitalopram." This property of enzymes has also been effectively used to resolve sterically hindered compounds by the introduction of a tether so that the enzyme-catalysed reaction can be performed at an artificially created, but less hindered, remote location. An example is the resolution of tertiary alcohols by the introduction of a glyoxylate ester. 

Camell and co-workers have recently applied lipase-catalysed resolution to formally desymmetrize prochiral ketones that would not normally be considered as candidates for enzyme resolution, through enantioselective hydrolysis of the chemically prepared racemic enol acetate. " For example, an NK-2 antagonist was formally desymmetrized by this approach using Pseudomonas fluorescens hpase (PFL) (Scheme 1.40). By recychng the prochiral ketone product, up to 82 % yields of the desired (5)-enol acetate (99 % ee) could be realized. This method offers a mild alternative to methodologies such as base-catalysed asymmetric deprotonation, which requires low temperature, and biocatalytic Baeyer-Villiger oxidation, which is difficult to scale up. 

Scheme 1.40 Access to NK-2 antagonists by the lipase-catalysed resolution of enol acetates...

Scheme 1.46 Lipase-catalysed diastereoselective acetylation of a posaconazole Intermediate...

Scheme 1.47 Lipase-catalysed desymmetrization of a posaconazole intermediate...

Reaction in organic solvent can sometimes provide superior selectivity to that observed in aqueous solution. For example, Keeling et al recently produced enantioenriched a-trifluoromethyl-a-tosyloxymethyl epoxide, a key intermediate in the synthetic route to a series of nonsteroidal glucocorticoid receptor agonist drug candidates, through the enan-tioselective acylation of a prochiral triol using the hpase from Burkholderia cepacia in vinyl butyrate and TBME (Scheme 1.59). In contrast, attempts to access the opposite enantiomer by desymmetrization of the 1,3-diester by lipase-catalysed hydrolysis resulted in rapid hydrolysis to triol under a variety of conditions. 

Roberts, N.J., Seago, A., Carey, J.S., Freer, R., Preston, C. and Lye, G.J., Lipase catalysed resolution of the lotrafiban intermediate 2,3,4,5-tetrahydro-4-methyl-3-oxo-lJS-l,4-benzodia-zepine-2-acetic acid methyl ester in ionic hquids comparison to the industrial f-butanol process. Green Chem., 2004, 6, 475 82. 

Hirose, Y., Kariya, K., Sasaki, I., Kurono, Y., Ebiike, H. and Achiwa, K., Drastic solvent effect on lipase-catalysed enantioselective hydroloysis of prochiral 1,4-dihydropyridines. 

Lingnal and gastric lipases catalyse only partial lipolysis to prodnce fatty acids and diacylglycerol. 

Both enantiomers of the oximes 353, R = (CH2)2CH=CH2, n = 1, 2 could be obtained in a pure form by lipase-catalysed kinetic resolution of its racemic oxime esters. Applying the previous sequence, both isomers of compounds 354 could be easily obtained. The synthesis of the framework of Histrionicotoxin 356 was obtained from 355 and is shown in equation 136. ... 

These differences are, e.g. a lowered melting point and a lowered dielectric constant [97]. If lipases are forced into this structured layer of water at the interface between water and oil by reducing the size of the reverse micelles (wi < 5), a lipase catalysed hydrolysis can be accelerated. On the other hand, the activity of oxidoreductases and their stabilities can decrease dramatically inside such small reverse micelles. 

Lipase catalysed hydrolysis of racemic esters of the important chiron solketal , 1, 2-0-isopropyhdene glycerol, are not very stereospecific due to the fact that they are primary esters. Secondary esters usually show much higher -values. Table 2.1 shows -... 

Anthonsen, T. and Jongejan, J. (1997) Solvent effect in lipase catalysed racemate resolution. Meth. Enzymol., 286, 473 95. 

Hansen, T.V., Waagen, V., Partali, V., Anthonsen, H.W. and Anthonsen, T. (1995) Cosolvent enhancement of enantioselectivity in lipase-catalysed hydrolysis of racemic esters. A process for production of homochiral C-3 building blocks using lipase B from Candida antarctica. Tetrahedron Asymmetry, 6, 499-504. 

Solvent effects in lipase-catalysed transesterification reactions. Acta Chem. Scand., 44, 1032-1035. 

Kvittingen, L., Sjursnes, B., Anthonsen, T. and Hailing, P. (1992) Use of salt hydrates to buffer optimal water level during lipase catalysed synthesis in organic media A practical procedure for organic chemists. Tetrahedron, 48,2793-2802. 

Recently, a lipase-catalysed kinetic resolution has been developed to produce L-tert-leucine via a lactone of its A-benzoyl derivative. There is also reputed to be another bioroute to L-terMeucine using transaminase technology. 

A method based on the use of PPL has been commercialised by DSM-Andeno and also other companies. Another mannfactnring process involving an epoxide intermediate is the lipase-catalysed resolution of the methyl ester of p-methoxyphenylglycidate, which is an intermediate in the process of Diltiazem, a cardiovascular dmg. 

Lipase-catalysed esterification instead of ester hydrolysis is also being used, a.o. by Glaxo Wellcome for a kinetic resolution that yields (IS, 2. -tranx-2-methoxycyelo-... 

Lipolysed milk fat was one of the first flavours produced with the help of enzymes. The original process was based on the controlled lipase-catalysed hydrolysis of cream [18]. For instance, Mucor miehei lipase possesses a high selectivity towards flavour-active short-chain fatty acids. Additionally, lipases that prefer long-chain fatty acids or lipases without particular preferences can be found. The free fatty acids produced can be isolated by steam distillation and further purified. Thus, it is possible to obtain pure short-chain fatty acids like butanoic, hexanoic, octanoic and decanoic acid. 

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