Lipase carboxylic acid amides

Acetyloxybenzyloxy [332] Cleavage Lipase RB 001-05 pH 5.8, rt Product after cleavage Carboxylic acid Amide Alcohol... 

An interesting new approach for making carboxylic acid amides is shown in Figure 3.9. Monsan and coworkers [18] used lipases from C. antarctica and Rhi-zomucor miehei as catalysts in the direct amidation reaction between free fatty adds and a secondary sugar amine (N-methyl-glucamine) in hexane. Such a reaction would be impossible in water since amide hydrolysis would predominate for thermodynamic reasons. Because free N-methyl-glucamine was insoluble in hexane, it was added as an ionic complex with the free fatty add. The enzymatic... 

Lipase-catalyzed synthesis of carboxylic acid amides in hexane [18]. 

This lactamization process can be promoted by enzymes such as pancreatic porcine lipase. Reduction of co-azido carboxylic acids leads to macrocyclic lactams. Although treatment of carboxylic acids with amines does not directly give amides, the reaction can be made to proceed in good yield at room temperature or... 

One of the most important characteristics of IL is its wide temperature range for the liquid phase with no vapor pressure, so next we tested the lipase-catalyzed reaction under reduced pressure. It is known that usual methyl esters are not suitable for lipase-catalyzed transesterification as acyl donors because reverse reaction with produced methanol takes place. However, we can avoid such difficulty when the reaction is carried out under reduced pressure even if methyl esters are used as the acyl donor, because the produced methanol is removed immediately from the reaction mixture and thus the reaction equilibrium goes through to produce the desired product. To realize this idea, proper choice of the acyl donor ester was very important. The desired reaction was accomplished using methyl phenylth-ioacetate as acyl donor. Various methyl esters can also be used as acyl donor for these reactions methyl nonanoate was also recommended and efficient optical resolution was accomplished. Using our system, we demonstrated the completely recyclable use of lipase. The transesterification took place smoothly under reduced pressure at 10 Torr at 40°C when 0.5 equivalent of methyl phenylthioacetate was used as acyl donor, and we were able to obtain this compound in optically pure form. Five repetitions of this process showed no drop in the reaction rate (Fig. 4). Recently Kato reported nice additional examples of lipase-catalyzed reaction based on the same idea that CAL-B-catalyzed esterification or amidation of carboxylic acid was accomplished under reduced pressure conditions. ... 

The third group of target molecules comprises chiral carboxylic acid and their derivatives esters, amides and nitriles. Enantiomerically pure esters are prepared in an analogous manner to the enantiomerically pure alcohols discussed earlier [i.e. by esterase- or lipase-catalyzed hydrolysis or (trans)esterification]. However, these reactions are not very interesting in the present context of cascade reactions. Amides can be produced by enantioselective ammoniolysis of esters or even the... 

Asymmetrization of a prochiral dicarboxylic acid diester catalyzed by lipases, where the stereo center of the product is located on the acyl side, becomes a single-step process because the polar carboxylic acid and/or amide formed are not well accepted as substrates by the Upase. One example is the enantioselective hydrolysis or ammonolysis of diethyl 3-hydroxyglutarate, as shown in Scheme 7.4, a reaction which leads to the formation of a precursor for the important chiral side chain of atorvastatin, lipitor [40, 41]. The S-enantiomer was formed with high e.e. (98%), but unfortunately this is the undesired enantiomer for the production of the pharmaceutically important product. Only a-chymotrypsin gave a predominance of the... 

Lipases Esters, amides Alcohols, carboxylic acids, alcohols, amines 22-26... 

However, the closely related amino acid 133 was not a substrate for either lipase (from pigs or Candida) but could be resolved with the proteolytic enzyme papain. This acted as an esterase, hydrolysing the methyl ester rather than the amide. Note that this kinetic resolution produces a single enantiomer of the carboxylic acid rather than the alcohol and that separation of 134 from 133 is very easy as the free acid can be extracted from organic solvents by aqueous base in which it is soluble as the anion. 

The synthesis of DPP-IV inhibitor Saxagliptin 5 also required (55)-5-amino-carbonyl-4,5-dihydro-lH-pyrrole-l-carboxylic acid, l-(l,l-dimethylethyl)ester 10 (Figure 16.3C). Direct chemical ammonolyses were hindered by the requirement for aggressive reaction conditions, which resulted in unacceptable levels of amide race-mization and side-product formation, while milder two-step hydrolysis-condensation protocols using coupling agents such as 4-(4,6-dimethoxy-l,3,5-triazin-2-yl)-4-methylmorpholinium chloride (DMT-MM) [41] were compromised by reduced overall yields. To address this issue, a biocatalytic procedure was developed based on the Candida antartica lipase B (CALB)-mediated ammonolysis of (55)-4,5-dihydro-lH-pyrrole-l,5-dicarboxylic acid, l-(l,l-dimethylethyl)-5-ethyl ester 9 with ammonium carbamate to furnish 10 without racemization and with low levels of side-product formation. 

Litjens MJJ, Straathof AJJ, Jongejan JA, Heijnen JJ (1999) Synthesis of primary amides by lipase-catalyzed amidation of carboxylic acids with ammonium salts in an organic solvent. Chem Commun 1255 -1256... 

Papain (and lipase) Amino Acid surfactants Ester or amide bond formation between arginine s a-carboxylic acyl group and fatty alcohols, glycerol (polyols), or fatty amines, respectively Infante et al., 2009... 

Amides Amines and carboxylic acids Synthesis of amines and carboxylic acids resolution of amides, acids and amines Lipase, esterase, protease... 

Hydrolases catalyze cleavage of substrates by the addition of water. This chapter focuses on hydrolases that cleave carboxylic acid derivatives such as esters and amides lipases, esterases, and proteases. By carrying out reactions in organic solvents without water, hydrolases can also catalyze acyl transfer reactions to make esters and amides. 

Lipases and esterases typically show selectivity toward the alcohol or amine part of a carboxylic acid derivative. Favored acyl groups are simple straight chains like acetate or butyrate. In contrast, proteases show higher specificity for the acyl part of a carboxylic acid derivative. Proteases contain a specificity pocket for the acyl group. For example, subtilisins and chymotrypsin favor ester and amides of phenylalanine esters. Another difference between the enzyme classes is that lipases and esterases catalyze hydrolysis of only esters, whereas proteases catalyze hydrolysis of both amides and esters. Several good books on hydrolases in organic synthesis are available [2-4]. 

Hydrolases (EC 3), without any doubt are one of the most common enzymes in the development of asymmetric transformations [15]. In particular, esterases, lipases, and proteases have allowed the development of efficient transformations for the production of different families of compounds in enantiomerically pure form such as alcohols, amines, amides, carboxylic acids, carbonates, and esters [16,17]. These facts have led to their successful use in some representative applications for the industrial sector [18]. Their high tolerances for nonnatural reaction conditions, particularly highlighted in their activity in organic media, make hydrolases a favorite class of enzymes for organic chemists. Moreover, their availability from a large number of commercial sources at reasonable prices, lack of cofactor dependency, and broad substrate specificity facilitate their acceptance in the scientific community. 

Selective hydrolysis of esters is a well-established procedure for the resolution of chiral carboxylic acids. Enzymes such as hydrolases, lipases and proteases are utilized. Due to their high selectivity for (5)-amino acids, proteases have been widely used in the selective transformations of amino acids and their derivatives. a-Chymotrypsin- a serine protease -catalyzes not only the hydrolysis of amide bonds, but also the cleavage of various esters, including a-alkyl-a-amino acid esters. One application is the synthesis of (5)-a-[ C]-methyltryptophan The anion synthesized by LDA-deprotonation of M-benzylidene tryptophan methyl ester (T) was alkylated with [ CJmethyl iodide to obtain the methyl A-benzylidene derivative 2, which was hydrolyzed under acidic conditions. Subsequent selective cleavage of the ester group with a-chymotrypsin provided the enantiomerically pure (5)-amino acid 3 in 33% radiochemical yield. 

Lipases are of remarkable practical interest since they have been used in numerous biocatalytic applications, such as kinetic resolution of alcohols and carboxyl esters (both in water and in non-aqueous media) [1], regioselective acylations of poly-hydroxylated compounds, and the preparation of enantiopure amino acids and amides [2, 3]. Moreover, lipases are stable in organic solvents, do not require cofactors, possess broad substrate specificity, and exhibit, in general, a high enantioselectivity. All these features have contributed to make hpases the class of enzyme with the highest number of biocatalytic applications carried out in neat organic solvents. 

It is possible to resolve amino acids through either the amino or carboxylate functionality. If salt formation is the method employed, then usually the corresponding functionality in the substrate is protected or masked to avoid interference. The more common approach is to use an enzyme such as an esterase or lipase to hydrolyze just one enantiomer of an ester or amide substrate (Scheme... 

The mechanism of amide- and ester-hydrolyzing enzymes is very similar to that observed in the chemical hydrolysis by a base. A nucleophilic group from the active site of the enzyme attacks the carbonyl group of the substrate ester or amide. This nucleophilic chemical operator can be either the hydroxy group of a serine (e.g., pig fiver esterase, subtifisin, and the majority of microbial lipases), a carboxyl group of an aspartic acid (e.g., pepsin) [3], or the thiol functionality of cysteine (e.g., papain) [4-6]. 

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