Enzymatic hydrolysis of used

Park, J. W.,Takahata, Y., Kajiuchi,T., and Akehata,T. 1992. Effects of Nonionic Surfactant on Enzymatic Hydrolysis of Used Newspaper. Biotech. Bioeng., 39,17-120. 

Other approaches to (36) make use of (37, R = CH ) and reaction with a tributylstannyl allene (60) or 3-siloxypentadiene (61). A chemicoen2ymatic synthesis for both thienamycia (2) and 1 -methyl analogues starts from the chiral monoester (38), derived by enzymatic hydrolysis of the dimethyl ester, and proceeding by way of the P-lactam (39, R = H or CH ) (62,63). (3)-Methyl-3-hydroxy-2-methylpropanoate [80657-57-4] (40), C H qO, has also been used as starting material for (36) (64), whereas 1,3-dipolar cycloaddition of a chiral nitrone with a crotonate ester affords the oxa2ohdine (41) which again can be converted to a suitable P-lactam precursor (65). 

Increasingly, biochemical transformations are used to modify renewable resources into useful materials (see Microbial transformations). Fermentation (qv) to ethanol is the oldest of such conversions. Another example is the ceU-free enzyme catalyzed isomerization of glucose to fmctose for use as sweeteners (qv). The enzymatic hydrolysis of cellulose is a biochemical competitor for the acid catalyzed reaction. 

In contrast to oxoesters, the a-protons of thioesters are sufficiently acidic to permit continuous racemization of the substrate by base-catalyzed deprotonation at the a-carbon. Drueckhammer et al. first demonstrated the feasibility of this approach by performing DKR of a propionate thioester bearing a phenylthiogroup, which also contributes to the acidity of the a-proton (Figure 4.14) [39a]. The enzymatic hydrolysis of the thioester was coupled with a racemization catalyzed by trioctylamine. Owing to the insolubility of the substrate and base in water, they employed a biphasic system (toluene/H2O). Using P. cepacia (Amano PS-30) as the enzyme and a catalytic amount of trioctylamine, they obtained a quantitative yield of the corresponding... 

Stereoinversion Stereoinversion can be achieved either using a chemoenzymatic approach or a purely biocatalytic method. As an example of the former case, deracemization of secondary alcohols via enzymatic hydrolysis of their acetates may be mentioned. Thus, after the first step, kinetic resolution of a racemate, the enantiomeric alcohol resulting from hydrolysis of the fast reacting enantiomer of the substrate is chemically transformed into an activated ester, for example, by mesylation. The mixture of both esters is then subjected to basic hydrolysis. Each hydrolysis proceeds with different stereochemistry - the acetate is hydrolyzed with retention of configuration due to the attack of the hydroxy anion on the carbonyl carbon, and the mesylate - with inversion as a result of the attack of the hydroxy anion on the stereogenic carbon atom. As a result, a single enantiomer of the secondary alcohol is obtained (Scheme 5.12) [8, 50a]. 

Enzymatic hydrolysis of waste paper process optimization using response surface methodology... 

Enzymes are the catalyst per excellence for reactions in water, which is their natural habitat. Moreover, the use of enzymes often circumvents the need for functional group protection and deprotection steps. For example, enzymatic hydrolysis of penicillin G to 6-APA (Fig. 2.30) proceeds in one step at ambient temperature while chemical deacylation requires three steps, a temperature of - 40 C and various stoichiometric reagents, leading to a high E factor. 

The introduction of metabolizable ester functions may be a very useful means of obtaining retention of the radiotracer within the target, as known for 99mTc-ECD. It may also help to eliminate nontarget radioactivity more rapidly. Therefore, systematic studies have been performed, in order to understand the enzymatic hydrolysis of oxotechnetium(V) complexes with up to four ester groups in the complex [205]. Fig. 30 shows the partial hydrolysis by pig liver esterase as is was observed for 1 2 complexes of derivatized dimercaptosuccinic acid complexes. 

In another approach, the alcohol moiety, formed by an enzymatic hydrolysis of an ester, can act as a nucleophile. In their synthesis of pityol (8-37a), a pheromone of the elm bark beetle, Faber and coworkers [17] used an enzyme-triggered reaction of the diastereomeric mixture of ( )-epoxy ester 8-35 employing an immobilized enzyme preparation (Novo SP 409) or whole lyophilized cells of Rhodococcus erythro-polis NCIMB 11540 (Scheme 8.9). As an intermediate, the enantiopure alcohol 8-36 is formed via kinetic resolution as a mixture ofdiastereomers, which leads to the diastereomeric THF derivatives pityol (8-37a) and 8-37b as a separable mixture with a... 

In addition to the enzymatic hydrolysis of esters, there also ample examples where an epoxide has been cleaved using a biocatalyst. As described by the Faber group [19], reaction of the ( )-2,3-disubstituted ds-chloroalkyl epoxide roc-8-40 with a bacterial epoxide hydrolase (BEH), led to the formation of vie-diol (2 ,3S)-8-41 (Scheme 8.11). The latter underwent a spontaneous cydization to give the desired product (2i ,3i )-8-42 in 92 % ee and 76 % yield. The same strategy was used with the homologous molecule rac-8-43, which afforded the THF derivative (2R,3R)-S-4S in 86% ee and 79% yield. 

A strategy to access lactones via enzymatic hydrolysis of y- and /3-hydroxy aliphatic nitriles to their corresponding acids with subsequent internal esterification was applied using commercially available enzymes from BioCatalytics Inc. A number of y- and /3-hydroxy aliphatic nitrile substrates (Table 8.11) were evaluated, with the greatest selectivity observed with y-hydroxy nonanitrile, which was converted by nitrilase NIT1003 to the precursor of the rice weevil pheromone in 30% yield, 88% ee with an enatiomeric ratio of = 23 [90],... 

In a different approach a super-high-throughput ee-assay was developed on the basis of chirally modified capillary array electrophoresis (CAE).90 CAE was used in the Human Genome Project, and commercially available instruments have been developed which comprise a high number of capillaries in parallel, for example the 96-capillary unit MegaBACE consisting of 6 bundles of 16 capillaries.91 The system can address a 96-well microtiter plate. It was adapted to perform ee-determinations of chiral amines, which are potentially accessible by catalytic reductive amination of ketones, transition metal catalyzed Markovnikov addition of ammonia, or enzymatic hydrolysis of acetamides (Scheme 14).90... 

Mainly, two principles are used in electrochemical pesticide biosensor design, either enzyme inhibition or hydrolysis of pesticide. Among these two approaches inhibition-based biosensors have been widely employed in analysis due to the simplicity and wide availability of the enzymes. The direct enzymatic hydrolysis of pesticide is also extremely attractive for biosensing, because the catalytic reaction is superior and faster than the inhibition [27],... 

Competitive immunoassays may also be used to determine small chemical substances [10, 11]. An electrochemical immunosensor based on a competitive immunoassay for the small molecule estradiol has recently been reported [11]. A schematic diagram of this immunoassay is depicted in Fig. 5.3. In this system, anti-mouse IgG was physisorbed onto the surface of an SPCE. This was used to bind monoclonal mouse anti-estradiol antibody. The antibody coated SPCE was then exposed to a standard solution of estradiol (E2), followed by a solution of AP-labeled estradiol (AP-E2). The E2 and AP-E2 competed for a limited number of antigen binding sites of the immobilized anti-estradiol antibody. Quantitative analysis was based on differential pulse voltammetry of 1-naphthol, which is produced from the enzymatic hydrolysis of the enzyme substrate 1-naphthyl phosphate by AP-E2. The analytical range of this sensor was between 25 and 500pg ml. 1 of E2. 

This type of reaction was used by Langenbeck24 to describe the mechanism underlying the enzymatic hydrolysis of a glycoside (Fig. 4). This... 

Fructose has a much sweeter taste than glucose, hence the transformation of glucose derived from enzymatic hydrolysis of starch from com, provides an alternative sweetener to sucrose (a disaccharide of glucose and fructose). This replaced the use of sugar cane by the US soft drinks and candy industry (and effectively destroyed the economy of Cuba in the process). 

A simple example in this class with which to begin is A,A-diethyl-m-to-luamide 0V,/V-dicthyl-3-mcthylbenzamidc, DEET, 4.82), an extensively used topical insect repellant. The hydrolysis product 3-methylbenzoic acid was detected in the urine of rats dosed intraperitoneally or topically with DEET. However, amide hydrolysis represented only a minor pathway, the major metabolites resulting from methyl oxidation and A-dealkylation [52], Treatment of rats with /V,/V-dicthylbcnzamidc (4.83), a contaminant in DEET, produced the same urinary metabolites as its secondary analogue, A-ethylbenzamide (see Sect. 4.3.1.2). This observation can be explained by invoking a metabolic pathway that involves initial oxidative mono-A-deethylation followed by enzymatic hydrolysis of the secondary amide to form ethylamine and benzoic acid [47], Since diethylamide was not detected in these experiments, it appears that A,A-diethylbenzamide cannot be hydrolyzed by amidases, perhaps due to the increased steric bulk of the tertiary amido group. 

---