Synthesis Of Amino Acid Esters Research Articles

Design and Characterization of In-One Protease-Esterase PluriZyme.

Proteases are abundant in prokaryotic genomes (~10 per genome), but their recovery encounters expression problems, as only 1% can be produced at high levels; this value differs from that of similarly abundant esterases (1-15 per genome), 50% of which can be expressed at good levels. Here, we design a catalytically efficient artificial protease that can be easily produced. The PluriZyme EH1AB1 with two active sites supporting the esterase activity was employed. A Leu24Cys mutation in EH1AB1, remodelled one of the esterase sites into a proteolytic one through the incorporation of a catalytic dyad (Cys24 and His214). The resulting artificial enzyme, EH1AB1C, efficiently hydrolysed (azo)casein at pH 6.5-8.0 and 60-70 °C. The presence of both esterase and protease activities in the same scaffold allowed the one-pot cascade synthesis (55.0 ± 0.6% conversion, 24 h) of L-histidine methyl ester from the dipeptide L-carnosine in the presence of methanol. This study demonstrates that active sites supporting proteolytic activity can be artificially introduced into an esterase scaffold to design easy-to-produce in-one protease-esterase PluriZymes for cascade reactions, namely, the synthesis of amino acid esters from dipeptides. It is also possible to design artificial proteases with good production yields, in contrast to natural proteases that are difficult to express.

Polyvinyl Alcohol–Trypsin as a Catalyst for Amino Acid Ester Synthesis in Organic Media

The bovine trypsin‐catalyzed synthesis of N‐α‐benzoyl‐DL‐arginine esters from N‐benzoyl‐DL‐arginine were studied in various organic solvents. Trypsin was immobilized to polyvinyl alcohol (PVA) by adsorption from its aqueous solutions. Immobilized enzyme showed higher catalytic activities than free enzyme for amino acid esterification in ethanol. The yield of ester is strongly dependent upon the PVA/trypsin ratio and water content in the reaction medium. The rate and equilibrium constant of the ester formation reaction are also dependent on water content.

Asymmetric synthesis of optically active decahydroisoquinolines useful in HIV-1 protease inhibitor synthesis

An efficient synthesis of amino acid ester 8 is described featuring an asymmetric aza-Diels-Alder reaction of diene 5 and chiral imine 6 which establishes the asymmetry at C-3. Hydrogenation of 7 provides 8 with the desired asymmetry at C-4a and C-8a.

Vitamin K prodrugs: 1. Synthesis of amino acid esters of menahydroquinone-4 and enzymatic reconversion to an active form.

The efficacy and toxicity of vitamin K depends on the pathway and the extent of enzymatic reductive activation to vitamin K hydroquinone, which is an essential cofactor for the synthesis of clotting factors. Parenteral use of vitamin K is impaired by its water insolubility. With the aim to improve delivery problems associated with menahydroquinone-4 (MKH, 2), an active form of menaquinone-4, N,N-dimethylglycine esters of 2 (1-mono, 4-mono, and 1,4-bis) were synthesized and assessed as potential water-soluble prodrugs for parenteral use. The esters can deliver the hydroquinone to its active site without a quinone reductive activation step. The hydrochloride salts of the esters were found to be quite soluble in water. The hydrolysis of the esters in 20% rat liver homogenate 9000 x g supernatant, rat plasma and phosphate buffer, pH 7.4, at 37 degrees C was kinetically studied in the presence and absence of an esterase inhibitor. The hydrolysis was catalyzed by esterases located in the rat liver and rat plasma and quantitatively yielded 2. These results suggest that esterification of 2 with N,N-dimethylglycine is a promising way for obtaining water-soluble prodrug forms of 2. Based on the high susceptibility to liver esterase, the esters are potential prodrugs for achieving the site-specific delivery of 2.

Enzymatic synthesis of amino acid ester of butyl α-D-glucopyranoside

The regiospecific enzymatic esterification of butyl α-D-glucopyranoside with trichloro 2,2,2 ethyl N-tBoc 4-amino butyrate was achieved using Lipozyme® avoiding time consuming protection-deprotection steps. The tBoc group was subsequently removed using trifluoroacetic acid, leading to the formation of butyl 6-0-(4-amino butyroyl)-α-D-glucopyranoside.

Agarose-chymotrypsin as a catalyst for peptide and amino acid ester synthesis in organic media

Chymotrypsin immobilised within agarose gels by multi-point covalent attachment is a useful catalyst for peptide or amino acid ester synthesis in mainly organic media. Moist gel beads (optionally containing one reactant) may be suspended in organic phases based on ethyl acetate, 1,1,1-trichloroethane or pentan-3-one.

ChemInform Abstract: Synthesis of Amino Acid Esters by Papain.

AbstractA wide range of N‐Boc amino acid esters, such as (I), can be prepared from the corresponding acids and alcohols using papain in a biphasic system.

Amino acid ester synthesis by immobilized ?-chymotrypsin

A screening of immobilized α-chymotrypsin preparations suitable for the synthesis of N-acetyl-L-tyrosine ethyl ester from N-acetyl-L-tyrosine and up to 99% ethanol was carried out. α-Chymotrypsin adsorbed to Sepharose LH-20 or covalently bound to Sepharose 4B (tresyl chloride activation) was found to be an efficient catalyst. A column packed with immobilized enzyme retained 60% of its initial activity after 6 days of operation in a cyclohexane-ethanol medium.

Synthesis of amino acid esters by papain

A wide range of N-Boc-amino add esters were synthesized from N-Boc-amino acids and alcohol using papain as catalyst. Suitable biphasic reaction mixtures were found for most amino acids to achieve high yield of ester synthesis. With N-Boc-L-aspartic and glutamic adds only the a carboxyl group is esterified, without racemisation.

Optimization of the enzymatic synthesis of amino acid esters. Reaction in polyphasic medium

N-acetyl-L-Tyrosine Ethyl Ester (ATEE) was synthesized from N-acetyl- l-Tyrosine and ethanol, with immobilized chymotrypsin as catalyst. For this purpose, a biphasic liquid reaction mixture consisting of an organic chloroform phase and an aqueous phase was used. This system allows the shift of the reaction equilibrium towards ATEE synthesis by achieving continuous ATEE extraction in the organic phase. Synthesis rates of up to 90% were obtained by optimizing the reaction conditions and controlling the pH of the aqueous phase.

Lipoamino acid. Synthesis of amino acid esters of phosphatidyl glycerols.

The synthesis of α′-glycine and α′-alanine esters of α-(L-α-phosphatidyl)glycerols with myristic acid, palmitic acid, and stearic acid substituents is described. The lipoamino acids were obtained by the simultaneous phosphorylation of a D-α,β-diglyceride and azidoacyl β-benzyl glycerol with phenylphosphoryl dichloride and pyridine, isolation of the (diacyl L-α-glyceryl), (azidoacyl β-benzylglyceryl)-phenylphosphate by column chromatography on silicic acid, and the removal of the protective phenyl and benzyl groups as well as the reduction of the azido to the amino group in one operation by catalytic hydrogenolysis with a mixture of palladium and platinum catalysts.Azidoacetyl β-benzyl glycerol and 2-azidopropionyl β-benzyl glycerol were prepared by acylating β-benzyl glycerol with azidoacetyl chloride and 2-azidopropionyl chloride, respectively, and separating the mixtures of azidoacyl and bis-azidoacyl β-benzyl glycerols by column chromatography on silicic acid.

Synthesis of Amino Acid-Esters of Phosphatidylglycerols

Synthesis of Amino Acid-Esters of Phosphatidylglycerols