Β-alanine Methyl Ester Research Articles

Molecular modification based on site-directed mutagenesis improves the substrate specificity of β-ester acyltransferase for L-carnosine synthesis

L-carnosine is a natural β-peptide compound with a wide range of important physiological functions. In this study, β-ester acyltransferase (As DmpA) can catalyze the reaction of β-amino acid methyl ester and β-amino acid methyl ester to form β-peptides and can also catalyze the reaction of β-amino acid methyl ester and L-histidine to form L-carnosine. Therefore, the reaction system will produce a variety of β-peptides, including L-carnosine. To solve this problem, the substrate specificity of As DmpA was improved by molecular modification to further increase the catalytic synthesis yield of L-carnosine. It was found that L341 W, L341K and L341R in saturated mutations increased the ability to catalyze L-carnosine synthesis. It was also found that the high proportion of L-histidine in the reaction system was conducive to the synthesis of L-carnosine. When the concentration ratio of L-histidine to β-alanine methyl ester hydrochloride is 140:10, the conversion rate of L-carnosine can reach more than 90%. When the concentrations of L-histidine and β-alanine methyl ester hydrochloride were 140 mM and 210 mM, respectively, the concentration of L-carnosine reached 105 mM by adding β-alanine methyl ester hydrochloride in batches, which increased the concentration of L-carnosine by 3.28 times compared with the nonbatch feeding. In conclusion, the ability of As DmpA to catalyze L-carnosine synthesis was improved by molecular modification technology and batch feeding methods, which provides an excellent method for the production of L-carnosine.

Temperature dependence studies and microscopic protonation constants of L-alanine and β-alanine in acetonitrile – water mixtures

Abstract L-alanine and β-alanine are important biological molecules and have zwitterion structure. In this study, L- alanine and β-alanine’s microscopic protonation constants and thermodynamic parameters (enthalpy, entropy, and free energy changes) for the proton–ligand systems of L-alanine methyl ester, β-alanine and β-alanine methyl ester have been determined at 5; 20; 35 °C, in ACN-water (25% ACN and 50% ACN (v/v)) mixtures at constant ionic strength of 0.1000 mol L–1 NaClO4 by potentiometric method. The results shown that, L-alanine and β-alanine’s microscopic protonation constants generally tend to decrease with temperature rise and their protonation reactions in ACN-water mixtures generally favor enthalpy-driven.

Synthesis of β-Lactam and Anomalous Minor Products in the (i-Pr)2NEt-Promoted Reaction of N-Chloroglycine Methyl Ester Derivative with Dichloroacetyl Chloride

Apart from the expected [2 + 2]-cycloaddition product, the reaction of N-chloro-N-(2-methoxy-2-oxoethyl)-β-alanine methyl ester with dichloroacetyl chloride in the presence of ethyl(diisopropyl)amine gave minor N-(1,2-dichloro-2-oxoethyl)-β-alanine methyl ester and (3E)-1,1,1-trichloro-4-(diisopropylamino)- but-3-en-2-one.

Synthesis of β-Peptide Standards for Use in Model Prebiotic Reactions.

A one-pot method was developed for the preparation of a series of β-alanine standards of moderate size (2 to ≥12 residues) for studies concerning the prebiotic origins of peptides. The one-pot synthesis involved two sequential reactions: (1) dry-down self-condensation of β-alanine methyl ester, yielding β-alanine peptide methyl ester oligomers, and (2) subsequent hydrolysis of β-alanine peptide methyl ester oligomers, producing a series of β-alanine peptide standards. These standards were then spiked into a model prebiotic product mixture to confirm by HPLC the formation of β-alanine peptides under plausible reaction conditions. The simplicity of this approach suggests it can be used to prepare a variety of β-peptide standards for investigating differences between α- and β-peptides in the context of prebiotic chemistry.

The investigation of thermosensitive properties of phosphazene derivatives bearing amino acid ester groups

In this study, a series of phosphazene derivatives having amino acid esters were synthesized from the reactions of amino acid esters with cyclophosphazenes. Hexachlorocyclotriphosphazene, (N3P3Cl6) and octachlorocyclotetraphosphazene (N4P4Cl8) have been reacted with carboxylic amino acid esters; glycine ethyl ester hydrochloride, glycine methyl ester hydrochloride, β-alanine ethyl ester hydrochloride, β-alanine methyl ester hydrochloride and methyl 6-aminohexanoate hydrochloride to obtain cyclophosphazene compounds containing amino acid esters as side groups. All obtained compounds (1–9) were characterized using spectroscopic methods and elemental analysis. The molecular structures of compounds 2, 5 and 6 were also characterized by X-ray crystallographic studies. Hydrolytic degradations of compounds (1–9) were observed by 31P NMR spectroscopy under acidic condition (pH = 1–3) and at body temperature (35–38 °C). Concentration-dependent lower critical solution temperatures (LCST) of compounds were examined to determine their thermosensitive behaviors in aqueous solution. It is found that all compounds degraded to harmless products such as amino acid, phosphates, ammonium salts. LCSTs of compounds 1, 2 and 6 were found to be around body temperature that is important for biomedical applications.

Polymerisation of β-alanine through catalytic ester–amide exchange

Herein we present the use of group (IV) metal alkoxides as catalysts for the polymerisation of esters of β-alanine and its derivatives. The influence of different group (IV) metal alkoxides, different esters, temperature and solvents on the polymerisation are investigated. The order in which the group (IV) metal alkoxides catalyse the polymerisation is: Hf(Ot-Bu)4⩾Zr(Ot-Bu)4>Ti(Oi-Pr)4>Ti(On-Bu)4. Polymers with the highest degree of polymerisation are obtained performing a neat polymerisation of β-alanine methyl ester in the presence of Hf(Ot-Bu)4 as a catalyst at 50°C. The polymerisation can also be carried out efficiently in solution, in different solvents and at higher reaction temperatures. This method could also be applied for the formation of other polypeptides.

New Bioconjugated Rhenium Carbonyls by Transmetalation Reaction with Zinc Derivatives

The transmetallation reaction between zinc dithiocarbamates and rhenium carbonyls has been used as a new strategy to link biomolecules to transition metals. The zinc(II) dithiocarbamate of isonipecotic acid (1) and the succinimidyl ester derivative (2) were prepared by straight forward procedures and were fully characterized by spectroscopic and X-ray diffraction methods, showing in both cases the presence of dinuclear complexes. Complex 2 reacted with all the primary and secondary amines studied (glycine methyl ester, β-alanine methyl ester, 1-(2-methoxyphenyl)piperazine and D-(+)-glucosamine) through the activated succinimidyl ester group, linking the metallic fragment with the biomolecule by the formation of a peptidic bond, and leading to the respective bioconjugated zinc complexes 3-6. In all cases, these zinc complexes could be isolated from the reaction medium by simple precipitation. These results evidence the potential of complex 2 to be used as a synthon to link the zinc dithiocarbamate fragment to biomolecules that contain an amine group. Complexes 3-6 were characterized by the usual spectroscopic methods and all data agree with the proposed structures, which do not contain significant interactions between the zinc fragment and the functional groups of these biomolecules. The transmetallation reaction between the zinc complexes 3-6 and the rhenium carbonyl [ReBr₃(CO)₃]²⁻ led to the expected rhenium dithiocarbamates 7-10 with no change in the organic dithiocarbamate fragments, confirming the viability of this reaction as a tool for linking biomolecules to transition elements. All complexes were characterized by spectroscopic methods and the crystal structure of 8 was studied by X-ray diffraction analysis. All data demonstrated that the biomolecule is positioned far away from the fac-{Re(CO)₃} fragment and the octahedral coordination around the metal is completed by the functionalized dithiocarbamate and a phosphine ligand. Finally, the analysis by ESI-MS spectrometry of the reaction between the zinc complex 4 and a water solution of [Re(H₂O)₃(CO)₃]+ at a very low concentration (10 ppm) showed that the transmetallation reaction took place even though the solubility of the zinc complex in water medium was as low as 0.66 ppm. This preliminary result supports the viability of this approach for the preparation of rhenium and technetium target specific radiopharmaceuticals since the preparation of these compounds are always performed in water medium.

Synthesis of new spherical and hemispherical oligosaccharides with polylysine core scaffold

A new spherical polylysine dendrimer generation 3 with acetyl cellobiose unit through a C6 spacer (TLACD3) was synthesized for the investigation of the structural effects on the specific biological activities such as anti-HIV and blood anticoagulant activities, which are our continuous research works. Tris(2-ethylamino)amine was used as an initiator of the core compound and was reacted with di- t-butoxycarbonyl lysine (di-boc-lysine) by the stepwise condensation according to the literature to give the polylysine dendrimer generation 3. Adipic acid monocellobiose ester as a model compound of oligosaccharide units was synthesized by the mono-esterification of adipic acid and 1-hydroxyl acetyl cellobiose. The adipic cellobiose was reacted with the deprotected polylysine dendrimer generation 3 to afford the spherical dendrimer with cellobiose unit (TLACD3) in the terminal. The hemispherical polylysine dendrimer generation 3 with acetylated cellobiose in the terminal through the C6 spacer (ALACD3) was also prepared from β-alanine methyl ester and di-boc-lysine by the same procedures as above. The spherical and hemispherical dendrimers have 24 and 8 terminal cellobiose units in each molecule, respectively, and the structure was characterized by NMR, IR, and MALDI TOF mass measurements. Although the hemispherical dendrimer ALACD3 had eight cellobiose units in a molecule, for the spherical dendrimer TLACD3, one cellobiose unit was eliminated partially from the molecule by the results of the MALDI TOF mass measurements.

3-[(3,4,5-Tribromo-1H-pyrrol-2-ylcarbonyl)amino]propanoic acid

The title compound, C8H7Br3N2O3, was synthesized by condensation of β-alanine methyl ester with 3,4,5-tribromo-2-trichloro­acetyl­pyrrole at room temperature, followed by saponification and acidification. In the crystal structure, inter­molecular N—H⋯O hydrogen bonds and weak O—H⋯Br hydrogen-bond inter­actions link the mol­ecules into extended ribbons parallel to the c axis.

3-[(4-Bromo-1-methyl-1H-pyrrol-2-ylcarbonyl)amino]propanoic acid

The title compound, C9H11BrN2O3, was synthesized by condensation of β-alanine methyl ester with 4-bromo-1-methyl-2-(tri­chloro­acetyl)­pyrrole at room temperature. In the crystal structure, intermolecular N—H⋯O and O—H⋯O hydrogen-bond interactions link the mol­ecules into extended ribbons parallel to the a axis.

3-(4-Bromo-1H-pyrrole-2-carboxamido)propanoic acid

The title compound, C8H9BrN2O3, was synthesized by condensation of β-alanine methyl ester with 4-bromo-2-(tri­chloro­acetyl)­pyrrole, followed by saponification and acidification. In the mol­ecule, all bond lengths and angles are normal. The crystal packing is stabilized by intermolecular N—H⋯O and O—H⋯O hydrogen bonds.

Synthesis and Crystal Structure of N-[(15,4R)-2-Oxo-pinanyl]-β-alanine Methylester

Abstract The title compound, N-[(lS,4R)-2-oxo-pinanyl]-β-alanine methylester, is an important starting material for the electrochemical preparation of chiral amidoalkylation reagents in the synthesis of chiral β-substituted β-amino acid derivatives. The investigation of its crystal structure reveals an arrangement of the carbonyl group and the amine function, which is influenced by a hydrogen bonding interaction. This conformation makes the molecule especially appropriate for further synthetical modification

Catecholamine-protein conjugates: isolation of 4-phenylphenoxazin-2-ones from oxidative coupling of N-acetyldopamine with aliphatic amino acids

4-Phenylphenoxazinones 4 were isolated after biomimetic oxidation, using diphenoloxidases of insect cuticle, mushroom tyrosinase, or after autoxidation of N-acetyldopamine ( 1 ) in the presence of β-alanine, β-alanine methyl ester or N-acetyl-L-lysine. They are formed presumably by addition of 2-aminoalkyl-5-alkylphenols 2 to the o-quinone of biphenyltetrol 3 which, in turn, arises from oxidative coupling of 1 . The structures of 4 present the first examples for the assembly of reasonably stable intermediates in the rather complex process of chemical modifications of aliphatic amino acid residues by o-quinones.

Specific Effects in Acid Catalysis by Polymeric Sulfonic Acids in the Hydrolysis of the Amino Ester and Related Compounds

Abstract The amino ester hydrolysis by polymeric sulfonic acids increased as the concentration ratio, Cester/Cacid, was lowered, and a maximum in the plot of the rate constant, k, against the Cester/Cacid ratio was attained near the ratio=0.4 in the case of the β-alanine methyl ester as well as in the case of γ-methyl l-glutamate. At this optimum concentration, the catalytic effect of polyvinylsulfonic acid (A), for example, in the hydrolysis of the β-alanine methyl ester was 16 times greater than that of hydrochloric acid, while the effect of polystyrenesulfonic acid was about 7 times greater. The catalytic effects of hydrochloric acid and ethanesulfonic acid were the same in all cases, and there was no such specific behavior as in the former. Furthermore, the catalytic efficiency of polyvinylsulfonic acid in amino ester hydrolysis increased with an increase in the polymer molecular weight, in contrast with the case of the carboxylic ester, while no such correlation was found in the polystyrenesulfonic acid. Besides, the catalytic effect of partially-neutralized polymeric sulfonic acid, polyvinylsulfonic acid especially, decreased remarkably with the degree of neutralization. These different kinds of behavior can be interpreted as being due to the difference in the expansion in solutions and in the geometrical distances between nearest-neighboring sulfonic acid groups on the polymer chain.

Studies on the syntheses of oxytocics. III. Syntheses of beta-alanine and 2-methyl-beta-alanine derivatives

A series of β-alanine methyl ester and 2-methyl-β-alanine methyl ester derivatives were prepared and their oxytocic activity was examined. Among the compounds tested, N-[2-(3-indolyl)ethyl]-2-methyl-β-alanine methyl ester possessed a high activity.