Enzymatic hydrolysis lipase

K2CO3, MeOH, reflux KCN, EtOH, reflux NH3, MeOH LiOH, THE, H2O enzymatic hydrolysis (Lipase)... 

This method involves equimolar amounts of (I) and (II), and organic base as the acceptor of liberated p-toluenesulfonic acid. Polymers with high molecular weights, and yields froiji 68 to 95% (depending on mol. weights) were characterized by GPC, H NMR spectroscopy and DSC. Their enzymatic hydrolysis (lipase, a- chymotrypsin) was studied. 

A number of examples of monoacylated diols produced by enzymatic hydrolysis of prochiral carboxylates are presented in Table 3. PLE-catalyzed conversions of acycHc diesters strongly depend on the stmcture of the substituent and are usually poor for alkyl derivatives. Lipases are much less sensitive to the stmcture of the side chain the yields and selectivity of the hydrolysis of both alkyl (26) and aryl (24) derivatives are similar. The enzyme selectivity depends not only on the stmcture of the alcohol, but also on the nature of the acyl moiety (48). 

Resolution of Racemic Amines and Amino Acids. Acylases (EC3.5.1.14) are the most commonly used enzymes for the resolution of amino acids. Porcine kidney acylase (PKA) and the fungaly3.spet i//us acylase (AA) are commercially available, inexpensive, and stable. They have broad substrate specificity and hydrolyze a wide spectmm of natural and unnatural A/-acyl amino acids, with exceptionally high enantioselectivity in almost all cases. Moreover, theU enantioselectivity is exceptionally good with most substrates. A general paper on this subject has been pubUshed (106) in which the resolution of over 50 A/-acyl amino acids and analogues is described. Also reported are the stabiUties of the enzymes and the effect of different acyl groups on the rate and selectivity of enzymatic hydrolysis. Some of the substrates that are easily resolved on 10—100 g scale are presented in Figure 4 (106). Lipases are also used for the resolution of A/-acylated amino acids but the rates and optical purities are usually low (107). 

In this case study, an enzymatic hydrolysis reaction, the racemic ibuprofen ester, i.e. (R)-and (S)-ibuprofen esters in equimolar mixture, undergoes a kinetic resolution in a biphasic enzymatic membrane reactor (EMR). In kinetic resolution, the two enantiomers react at different rates lipase originated from Candida rugosa shows a greater stereopreference towards the (S)-enantiomer. The membrane module consisted of multiple bundles of polymeric hydrophilic hollow fibre. The membrane separated the two immiscible phases, i.e. organic in the shell side and aqueous in the lumen. Racemic substrate in the organic phase reacted with immobilised enzyme on the membrane where the hydrolysis reaction took place, and the product (S)-ibuprofen acid was extracted into the aqueous phase. 

The above-mentioned facts have important consequences on the stereochemical outcome of the kinetic resolution of asymmetrically substituted epoxides. In the majority of kinetic resolutions of esters (e.g. by ester hydrolysis and synthesis using lipases, esterases and proteases) the absolute configuration at the stereogenic centre(s) always remains the same throughout the reaction. In contrast, the enzymatic hydrolysis of epoxides may take place via attack on either carbon of the oxirane ring (Scheme 7) and it is the structure of the substrate and of the enzyme involved which determine the regioselec-tivity of the attack [53, 58-611. As a consequence, the absolute configuration of both the product and substrate from a kinetic resolution of a racemic... 

Fig. 13.11 Schematic representation of the hollow fiber membrane biorector for the enzymatic hydrolysis of triglycerides. A hydrophilic membrane has been used, coated with lipase on the lipid side [85].

Effect of the Particle Size of PEA Powders on the Hydrolysis by R. delemar Lipase. In the case of PEA, small particles were hydrolyzed better than large ones as shown in Figure 3. So it was assumed that the enzymatic hydrolysis depends on the amounts of surface area of polyester powders. 

Effect of Molecular Weight of Polyester on the Hydrolysis by Rhizopus lipase. Using three kinds of polyesters, PCL-diol (I), polyhexameth-ylene adipate (II), and a copolyester (ill) made from 1,6-hexamethyl-enediol and a 70 30 molar ratio mixture of e- caprolactone and adipic acid, the effects of the of polyester on the hydrolysis by lipase were examined (Figure k) Mn did not affect the rates of hydrolysis by R. arrhizus and delemar lipases when Vln was more than about UOOO. This would indicate these lipases randomly splits ester bonds in pol-mer chains. In contrast, when TEi was less than about i4000 2 the rates of the enzymatic hydrolysis were faster with the smaller Mn of polyesters. This corresponded to the fact that Tm was lower with the smaller Mn of polyesters. 

An interesting example of biocatalysis and chemical catalysis is the synthesis of a derivative of y-aminobutyric acid (GABA) that is an inhibitor for the treatment of neuropathic pain and epilepsy (Scheme 10.4). The key intermediate is a racemic mixture of cis- and trons-diastereoisomer esters obtained by a hydrogenation following a Horner-Emmons reaction. The enzymatic hydrolysis of both diaste-reoisomers, catalyzed by Candida antarctica lipase type B (CALB), yields the corresponding acid intermediate of the GABA derivative. It is of note that both cis- and trans-diastereoisomers of the desired enantiomer of the acid intermediate can be converted into the final product in the downstream chemistry [10]. 

Herzog K, Muller RJ, Deckwer WD (2006) Mechanism and kinetics of the enzymatic hydrolysis of polyester nanoparticles by lipases. Polym Degrad Stab 91 2486-2498... 

The stability of the ester surfactants against enzymatic hydrolysis by two different microbial Upases, Mucor miehei lipase (MML) and Candida antarc-tica lipase B (CALB) added separately to the surfactant solutions, was also investigated, see Fig. 5 [19]. It is obvious that hydrolysis of the unsubstituted surfactant is much faster with both CALB and MML than that of the substituted surfactants, i.e., increased steric hindrance near the ester bond leads to decreased hydrolysis rate. Since the specificity of the enzyme against its substrate is determined by the structure of the active site, it can be concluded, as expected, that the straight chain surfactant most easily fits into the active site of both enzymes. 

Albro, P.W. Thomas, R.O. (1973) Enzymatic hydrolysis of di-(2-ethylhexyl) phthalate by lipase. Biochim. biophys. Acta, 360, 381-390... 

Optically active aziridines have been prepared in high enantiomeric excess by the enzymatic resolution of meso diesters (94AG(E)599). For example, when the me o-bis(acetoxymethyl)aziridine (56) was subjected to enzymatic hydrolysis with lipase Amano P, the aziridine (57) was obtained in 98% ee (90TL6663). 

Enzymatic Hydrolysis. Enzymatic hydrolysis has received enormous attention. The enzymes generally employed are lipases from microorgan isms, plants, or mammalian liver. The great advantage of the enzymatic process is its high chemo- and stereoselectivity. 

Enzymatic hydrolysis is a nondestructive alternative to saponification for removing triglycerides in vitamin K determinations. For the simultaneous determination of vitamins A, D, E, and K in milk- and soy-based infant formulas and dairy products fortified with these vitamins (81), an amount of sample containing approximately 3.5-4.0 g of fat was digested for 1 h with lipase at 37°C and at pH 7.7. This treatment effectively hydrolyzed the glycerides, but only partially converted retinyl palmitate and a-tocopheryl acetate to their alcohol forms vitamin D and phyllo-quinone were unaffected. The hydrolysate was made alkaline in order to precipitate the fatty acids as soaps and then diluted with ethanol and extracted with pentane. A final water wash yielded an organic phase containing primarily the fat-soluble vitamins and cholesterol. 

Neri et al89 reported the desymmetrization of A-Boc-serinol 98 by the selective monoacetylation using PPL (porcine pancreas lipase) and vinyl acetate as the acylating agent in organic solvent. The mono acetylated product (R)-99 was obtained after 2 hours with 99% ee and isolated in 69% chemical yield. Traces of the diacetylated product 100 were observed. The cyclization of (R)-99 in basic medium afforded the racemic oxazolidinone 101. The latter was subjected to enzymatic hydrolysis in phosphate buffer affording (R)-... 

Dissolution and Separation by Special Applications Enzymes and Microextraction Several enzymes such as trypsin, protease type XIV, lipase and/or cellulase, are used for enzymatic hydrolysis. For the determination of Hg2+ and Me-Hg in fish... 

Scriba GKE (1993) In-Vitro evaluation of 4-(2-glyceryl)-butyric acid for lipase-driven drug delivery. Pharm Res 10 S295 Udata C, Tirucherai G, Mitra AK (1999) Synthesis, stereoselective enzymatic hydrolysis and skin permeation of... 

Scheme 3 provides a specific example of the enzymatic hydrolysis outlined in Scheme 1. The substituted allylic acetate is hydrolyzed with a lipase from Pseudomonas fluorescens in a phosphate buffer in the presence of 5 mol% palladium complex.

Enzymatic syntheses of CPS have also been reported, using various lipase-catalyzed transacylations [69]. Interestingly, a biotechnological process to obtain natural vanillin from CPS has been developed, capitalizing on the enzymatic hydrolysis of CPS and the oxidation of vanillamine with a flavoprotein vanillyl alcohol oxidase [70]. 

Chlorotetaine is an irreversible inhibitor of glucosamine-6-phosphate synthetase and thereby interferes with ceil wall biosynthesis. The terminal steps of a synthesis of Chlorotetaine are shown in Scheme 6.15 in which deprotection of an iV-terminal amino group is a prelude to the final enzymatic hydrolysis of a methyl ester function.43 Critical to the success of the synthesis was the suppression of easy racemisation at the ring juncture in the ester hydrolysis step by using porcine pancreatic lipase. 

---