Lipase cleavage

Lipase Cleavage of Triglycerides Aspergillus ssp. Penicillin roque-fortii Production of Enzyme Modified Cheese (EMC) Chedar flavour... 

Chromobacterium viscosum lipase, cyclohexane, vinyl acetate, THF, 40°." Cleavage... 

Lipase from Aspergillus niger, 0.2 M phosphate buffer, acetone, pH 7, 37°, 50-96% yield. This lipase was used in the cleavage of phosphopeptide heptyl esters. These conditions are sufficiently mild to prevent the elimination of phosphorylated serine and threonine residues." ... 

This ester was developed to impart greater hydrophilicity in C-terminal peptides that contain large hydrophobic amino acids, since the velocity of deprotection with enzymes often was reduced to nearly useless levels. Efficient cleavage is achieved with the lipase from R. niveus (pH 7, 37°, 16 h, H2O, acetone, 78-91% yield)... 

Preparation of PhAcOZ amino acids proceeds from the chloroformate, and cleavage is accomplished enzymatically with penicillin G acylase (pH 7 phosphate buffer, 25°, NaHS03, 40-88% yield). In a related approach, the 4-ace-toxy derivative is used, but in this case deprotection is achieved using the lipase, acetyl esterase, from oranges (pH 7, NaCl buffer, 45°, 57-70% yield). 

The synthesis in Scheme 13.41 is also built on the desymmetrization concept but uses a very different intermediate. cA-5,7-Dimethylcycloheptadiene was acetoxylated with Pd(OAc)2 and the resulting all-cA-diacetate intermediate was enantioselectively hydrolyzed with a lipase to give a monoacetate that was protected as the TBDMS ether. An anti Sw2 displacement by dimethyl cuprate established the correct configuration of the C(2) methyl substituent. Oxidative ring cleavage and lactonization gave the final product. 

The multipolymer enzymatic resolution of soluble polymer-supported alcohols 42 and 43 was achieved using an immobilised lipase from Candida Antarctica (Novozym 435). The R-alcohol was obtained in enantiomerically pure form (>99% ee) after its cleavage from the poly(ethylene) glycol (PEG) scaffold . The achiral hydantoin- and isoxazoline-substituted dispirocyclobutanoids 47 were produced using both solution and solid-phase synthesis <00JOC3520, OOCC1835>. 

Lipase-catalyzed cleavage of glycopeptide n-heptyl esters was successfully used in syntheses of multiple glycosylated (9-glycopeptides (103). Surpris-... 

With a good route to the key meso diol 128 in hand, the authors turned their attention to desymmetrization, using the known asymmetric hydrolysis of meso diacetates by Lipase AK (Scheme 23). The meso diol 128 was first converted to diacetate 140, and then hydrolyzed with Lipase AK to cleave selectively one of the two acetates, producing chiral hydroxyester 141. Oxidation, cleavage of the acetate, and lactonization yielded the (3S,4.R) lactone 129. The corresponding lactol (3S,4 )-130 was found to be the enantiomer of the compound produced in the HLADH synthesis. 

The linker (49) is attached as an amide to the solid phase. Cleavage of the acyl group by a lipase generated a phenolate (50), which fragments to give a quinone methide (51) and releases the product (52). The quinone methide remains on the solid phase and is trapped by water or an additional nucleophile. 

Lipases (EC 3.1.1.3) are ubiquitous enzymes belonging to the esterase class of hydrolases (see earlier section) and are found in most hving organisms. In nature, lipases catalyze the hydrolytic cleavage of triglycerides into fatty acids and glycerol, or into fatty acid and mono- or diglyceride, at a water-oil interface (Scheme 6.4). 

Fats (triacylglycerols) are mainly attacked by pancreatic lipase at positions 1 and 3 of the glycerol moiety. Cleavage of two fatty acid residues gives rise to fatty acids and 2-mono-acylglycerols, which are quantitatively the most important products. However, a certain amount of glycerol is also formed by complete hydrolysis. These cleavage products are resorbed by a non-ATP-dependent process that has not yet been explained in detail. 

Various factors are required for regular fat digestion. Sublingual lipase and eventually a gastric lipase — which are both stable in an acidic environment — start digesting dietary fats in the stomach. In the intestine, pancreatic bicarbonate as well as bile acids are essential for emulsification of fats and fat-soluble substances which are then cleaved by pancreatic lipases. The cleavage products are incorporated into micelles and can then penetrate the unstirred water layer (UWL) which covers the intestinal surface. There, they can deliver the cleavage products of dietary fats as well as fat-soluble substances (e.g., carotenoids, vitamin E, vitamin A) to the luminal surface of the enterocytes. 

Spectrophotometric assays can be used for the estimation of the enantiosel-ectivity of enzymatic reactions. Reetz and coworkers tested 48 mutants of a lipase produced by epPCR on a standard 96-well microtiter plate by incubating them in parallel with the pure R- and S-configured enantiomers of the substrate (R/S-4-nitrophenol esters) [10]. The proceeding of the enzyme catalyzed cleavage of the ester substrate was followed by UV absorption at 410 nm. Both reaction rates are then compared to estimate the enantiomeric excess (ee-value). They tested 1000 mutants in a first run, selecting 12 of them for development of a second generation. In this way they were able to increase the enantiomeric excess from 2% for the first mutants to 88% after four rounds of evolutive optimization. 

Lipase-catalyzed enantioselective ring cleavage of racemic cis- and rra r-13-azabicyclo[10.2.0]tetradecan-14-one has given enantiopure /3-aminoacids and /3-lactams (see Section 2.04.6.4) <2006TA3193>. 

Lipases are a special class of esterases that also catalyze the hydrolytic cleavage of ester bonds, but differ in their substrate spectrum. Lipases have the special capability to catalyze the hydrolysis of water-insoluble substrates such as fats and lipids. Like many other enzyme-catalyzed reactions, the ester hydrolysis is a reversible process, which allows using lipases and other esterases for the synthesis of esters. The use of lipases as catalysts in synthetic chemistry is described elsewhere in this chapter. 

This chapter consequently focuses on the application of enzymes for the selective cleavage of esters, amides and nitriles [2], Out of all the reported industrial applications of enzymes these type of hydrolyses constitute more than 40% [3], Enzymatic hydrolyses are often performed because of the enantioselectivity of enzymes, and in particular of the lipases that are used for the production of enantiopure fine chemicals. 

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