Amino Acid Ethyl Esters Research Articles

"First Come, First Served" and Threshold Effects in a Central-to-Planar-to-Helical Hierarchical Chiral Induction.

Perylene diimide tethered pillar[5]arene derivatives form aggregates in non-polar organic solvents, and the complexation of cationic amino acid ethyl ester (cAA-OEt) with the aggregates induce a central-to-planar-to-helical chirality transfer, leading to intensive circular dichroism (CD) signals having dissymmetric factors (gabs ) of up to 3.67×10-2 . The hierarchical chiral induction exhibited an intriguing threshold dose effect, namely, the chiral induction does not occur in the low concentration range of cAA-OEt but is triggered when cAA-OEt exceeds a threshold concentration. The inhibited interconversion between the Rp and Sp conformers of pillar[5]arene, which is further restricted in the aggregation, plays a crucial role in the threshold effect. When adding enantiopure cAA-OEt first to the threshold concentration and then adding an equal amount of the antipodal cAA-OEt to give cAA-OEt in racemic form, CD spectra having the same sign as the CD induced by first adding pure cAA-OEt were induced, thus showing an unprecedented "first come, first served" effect.

“First Come, First Served” and Threshold Effects in a Central‐to‐Planar‐to‐Helical Hierarchical Chiral Induction

AbstractPerylene diimide tethered pillar[5]arene derivatives form aggregates in non‐polar organic solvents, and the complexation of cationic amino acid ethyl ester (cAA‐OEt) with the aggregates induce a central‐to‐planar‐to‐helical chirality transfer, leading to intensive circular dichroism (CD) signals having dissymmetric factors (gabs) of up to 3.67×10−2. The hierarchical chiral induction exhibited an intriguing threshold dose effect, namely, the chiral induction does not occur in the low concentration range of cAA‐OEt but is triggered when cAA‐OEt exceeds a threshold concentration. The inhibited interconversion between the Rp and Sp conformers of pillar[5]arene, which is further restricted in the aggregation, plays a crucial role in the threshold effect. When adding enantiopure cAA‐OEt first to the threshold concentration and then adding an equal amount of the antipodal cAA‐OEt to give cAA‐OEt in racemic form, CD spectra having the same sign as the CD induced by first adding pure cAA‐OEt were induced, thus showing an unprecedented “first come, first served” effect.

Monomer Choice Influences N-Acryloyl Amino Acid Grafter Conversion via Protease Catalysis.

End-capped peptides modified with reactive functional groups on the N-terminus provide a route to prepare peptide-polymer conjugates for a broad range of applications. Unfortunately, current chemical methods to construct modified peptides rely largely on solid-phase peptide synthesis (SPPS), which lacks green preparative characteristics and is costly, thus limiting its applicability to specialty applications such as regenerative medicine. This work evaluates N-terminally modified N-acryloyl-glutamic acid diethyl ester, N-acryloyl-leucine ethyl ester, and N-acryloyl-alanine ethyl ester as grafters and papain as the protease for the direct addition of amino acid ethyl ester (AA-OEt) monomers via protease-catalyzed peptide synthesis (PCPS) and the corresponding formation of N-acryloyl-functionalized oligopeptides in a one-pot aqueous reaction. It was hypothesized that by building N-acryloyl grafters from AA-OEt monomers that are known to be good substrates for papain in PCPS, the corresponding grafters would yield high grafter conversions, high ratio of grafter-oligopeptide to free NH2-oligopeptide, and high overall yield. However, this work demonstrates based on the grafter/monomers studied herein that the dominant factor in N-acryloyl-AA-OEt grafter conversion is the co-monomer used in co-oligomerizations. Computational modeling using Rosetta qualitatively recapitulates the results and provides insight into the structural and energetic bases underlying substrate selectivity. The findings herein expand our knowledge of factors that determine the efficiency of preparing N-acryloyl-terminated oligopeptides by PCPS that could provide practical routes to peptide macromers for conjugation to polymers and surfaces for a broad range of applications.

Stereoselective synthesis of backbone extended π-conjugated amino esters.

Utilization of the Wittig reaction to synthesize conjugative multiple double bonds is rare. We examined the utility of the Wittig reaction to construct conjugative two and three carbon-carbon double bonds on the N-protected amino acid backbone. The ethyl esters of N-Boc amino acids with multiple carbon-carbon double bonds in the backbone were isolated in excellent yields with exceptional E-selectivity of the double bonds. The allylic alcohols of α,β-unsaturated γ-amino esters were selectively synthesized from the DIBAL-H and BF3·OEt2. The allylic alcohols were transformed into aldehydes using IBX oxidation. Using this protocol, we synthesized ethyl esters of N-Boc-(E,E)-α,β,γ,δ-unsaturated ε-amino acids with various side-chain functionalities and ethyl esters of N-Boc-(E,E,E)-α,β,γ,δ,ε,ζ-unsaturated η-amino acids with excellent yields. We speculated the exceptional E-selectivity is probably due to the stabilization of the planar transition state of the Wittig reaction with the double bond p-orbitals. No racemization was observed in the synthesis of amino acids. The reported process may serve as an excellent route to synthesize multiple conjugative carbon-carbon double bonds.

Synthesis of p-coumaroyl amino acid derivatives and evaluation of their anti-oxidative and anti-tyrosinase activities

P-coumaroyl amino acid ethyl esters (p-CAAEEs, ãf) were successfully synthesized with p-coumaric acid (p-Coa) and amino acid ethyl ester hydrochloride under the catalysis of 1-ethyl-3- (dimethylaminopropyl) carbodiimide hydrochloride (EDC) and 1-hydroxybenzotriazole (HOBt). The new derivatives were characterized by FT-IR, 1H NMR, and UPLC-MS spectroscopy techniques. The antioxidative activities of p-CAAEEs were evaluated in terms of scavenging capabilities of DPPH, hydroxyl and ABTS radicals. Among these compounds, d and f exhibited the stronger strength to scavenge free radicals. In addition, their anti-tyrosinase activities were determined through monophenolase and diphenolase experiments. In the anti-tyrosinase diphenolase experiment, all p-CAAEEs had stronger inhibitory abilities than that of p-Coa. In particular, compound f exhibited potential both anti-oxidative and anti-tyrosinase activities.

Amino Acid Ester based Phenolic Ionic Liquids as a Potential Solvent for the Bioactive Compound Luteolin: Synthesis, Characterization, and Food Preservation Activity

Ionic liquids (ILs) have gained great attention as potent solubilizing agents of poorly soluble bioactive compounds. The use of Luteolin (LUT) – a natural bioactive compound – is limited because of its poor aqueous solubility. To address this issue, this study reports potential ILs for effectively solubilizing LUT at ambient temperature. First, promising ILs were screened from a potential 180 ILs that were proposed by the combination of 20 standard amino acid ethyl esters cations and nine phenolic acids anions using the conductor-like screening model for real solvents (COSMO-RS); the activity coefficients of LUT at infinite dilution in ILs were used as the screening criteria. Four proline ethyl ester phenolate ILs (PEEP-ILs) composed of a biocompatible proline ethyl ester and bioactive phenolic acids (trans-ferulic, vanillic, p-coumaric, and 4-hydroxybenzoic acid) were selected and synthesized. The synthesized PEEP-ILs were characterized through 1H NMR, FT-IR, elemental analysis, TGA, and DSC. The experimental solubility of LUT in PEEP-ILs (60% IL in water) showed excellent solubility. Among the PEEP-ILs, proline ethyl ester ferulate (IL[ProEt][Fer]) exhibited the best LUT solubility, followed by ILs with p-coumarate (IL[ProEt][Cou]), vanillate (IL[ProEt][Van]), and 4-hydroxybenzoate (IL[ProEt][Ben]). 1H NMR assessment and COSMO-RS prediction confirmed that the ILs facilitated the solubilization of LUT through multiple hydrogen bonding, π − π, and cation − π interactions between the LUT and the ILs. The biocompatibility study revealed that PEEP-ILs were relatively harmless and low toxicity compared with conventional imidazolium, pyridinium, pyrrolidinium, piperidinium, and morpholinium-based ILs. The LUT dissolved in the newly-synthesized PEEP-ILs and demonstrated better organoleptic properties on red apple slices. These results indicate that PEEP-ILs can be potential green alternatives to conventional toxic solvents for dissolving poorly water-soluble bioactive natural preservatives.

Juvenile hormone mimics with phenyl ether and amide functionality to be insect growth regulators (IGRs): synthesis, characterization, computational and biological study

A series of substituted phenyl ethers derivatives as juvenile hormone (JH) mimics (V1-V8) have been synthesized. Substituted phenoxyacetic acid and amino acid ethyl ester hydrochloride were prepared using NaOH, SOCl2. DCC method has been used for amide linkage. The structure of prepared compounds has been confirmed by Fourier Transform Infra-Red (FT-IR), Electrospray ionization-Mass spectrometry (ESI-MS), Proton and Carbon-13 nuclear magnetic resonance (1H-NMR, 13C-NMR) spectroscopic techniques. Biological efficacy of synthesized analogs has been carried out under laboratory conditions. Galleria mellonella (honey bee pest) has been chosen as testing insect. Juvenile hormone (JH) activity of synthesized compounds has been tested at different concentrations and compared with the standard juvenile hormone analogs (JHAs) pyriproxyfen (M1) and fenoxycarb (M2) against the fifth larval instar of G. mellonella. Compound ethyl 2-[2-(4-methylphenoxy)aminoacetyl]-3-phenyl-propanoate (V6) exhibited better activity among all the synthesized compounds (V1-V8) with LC50 and LC90 values of 0.11 mg/mL and 0.56 mg/mL respectively. Compounds showed insect growth regulating (IGR) activity at lower concentrations. In silico screening of all synthesized compounds with the W-cavity of juvenile hormone-binding protein (JHBP) of insect G. mellonella has been carried out. Chemical reactivity of synthesized series has been studied using DFT/B3LYP/6-311 + G(d,2p) method. Non-toxic behavior of molecules has also been observed from ADMET (Absorption, Distribution, Metabolism, Excretion, and Toxicity) study using discovery studio client 3.0. Communicated by Ramaswamy H. Sarma

The influence of ultrasonic irradiation on catalytic performance of ZnO nanoparticles toward the synthesis of chiral 1‐substituted‐1H‐tetrazolederivatives from α‐amino acid ethyl esters

AbstractIn this work, a simple and greener protocol for the synthesis of 1‐substituted 1H‐tetrazole derived from α‐amino acid ethyl esters was demonstrated in the presence of zinc oxide nanoparticles (ZnO NPs) under conventional conditions, with heating (at 60 and 80°C and under reflux) compared with ultrasonic. The effect of solvent was investigated to reveal that the solvent system CH3CN/H2O was optimum to obtain 1‐substituted 1H‐tetrazole in high yield. In addition, the effect of irradiation power was studied, which showed that the yield of the reaction was improved at 200 W and the reaction time was shortened to be 30 min. Also, an improvement in the rate of the reaction and the yield of the products was observed when reactions were carried out under sonication conditions in the presence of ZnO NPs compared with conventional methods using various zinc salts as catalysts. The yields of tetrazole compounds 2a–i under sonication were determined (88–96%). Furthermore, the investigated heterogeneous catalytic system was recycled and reused for five runs with significant production of tetrazole 2a as a model target compound in excellent yields at each reaction cycle. In general, the investigated synthetic strategy for the heterocyclization of α‐amino acid ethyl ester derivatives to 1‐substituted 1H‐tetrazoles was in agreement with the green chemistry point of view.

Stereospecific Synthesis of 3,4-Dihydro-2H-naphtho-1,4-oxazin-2-ones by Unification of Benzoxepine-4-carboxylates with Chiral Amino Acid Ethyl Esters.

A novel and efficient stereocontrolled method has been developed for the preparation of chiral 3,4-dihydro-2H-naphtho[1,2-b][1,4]oxazin-2-ones by the reaction of benzoxepine-4-carboxylates with chiral amino acid ethyl esters for the first time. The chiral 3,4-dihydro-2H-naphtho-1,4-oxazinones have been achieved in one step by the formation of C-N, C-C, and C-O bonds.

Synthesis of N-hydroxycinnamoyl amide derivatives and evaluation of their anti-oxidative and anti-tyrosinase activities

Twelve N-hydroxycinnamoyl amino acid amide ethyl esters (CAES) were synthesized by using l-amino acid ethyl ester hydrochloride and corresponding cinnamic acid (ferulic acid, acetylferulic acid and caffeic acid) as raw materials in the presence of a catalytic amount of 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide-hydrochloride (EDC) and 1-hydroxybenzotriene (HOBt). The 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging activities of CAES were evaluated. The anti-tyrosinase activities of N-feruloyl amino acid ethyl esters and the hydroxyl (OH) free radical scavenging activities of N-caffeoyl amino acid ethyl esters were also examined. DPPH free radical scavenging activity was shown in all CAES, of which N-caffeoyl amino acid ethyl esters demonstrated higher radical scavenging activity than N-feruloyl amide derivatives, and (E) -N-(caffeic acid)-l-glycinate ethyl ester (c5) had the strongest ability to scavenge free radicals with an IC50 value of 18.6 µM. The acetylferuloyl amino acid esters exhibited the highest tyrosinase inhibition activity among the tested amides.

Catalyst-free three-component synthesis of new pyrrolidine derivatives via 1,3-dipolar cycloaddition

Differently substituted pyrrolidine derivatives have been prepared by a three-component reaction of heterocyclic aldehydes, amino acid methyl or ethyl esters, and trans -1,2-dibenzoylethylene in toluene under catalyst-free conditions. This simple one-step procedure allows to obtain the desired 3,4-dibenzoyl-5-hetarylpyrrolidines in high yields ensuring high diastereoselectivity. Given the fact that the fundamental stage of the proposed reaction mechanism is based on 1,3-dipolar cycloaddition, DFT and TDDFT quantum-chemical calculations have been used for better understanding and characterization of geometry and electronic structure of the reaction intermediates and products.

Facile Synthesis and Biological Evaluation of Novel N-Nitro Urea Derivatives Incorporating Amino Acid Ethyl Esters

<span lang=PT-BR style=font-size:10.0pt;color:black;mso-font-kerning:0pt;mso-ansi-language: PT-BR> <span style=font-size:11.0pt;mso-fareast-font-family: times= new= roman;color:black;mso-font-kerning:0pt=>1. <span style=font-size:11.0pt;color:black; mso-font-kerning:0pt>Abstract A novel series of N - nitro urea derivatives 6a-w containing various amino acid ethyl esters <span style=font-size:10.0pt;mso-font-kerning: 0pt> were conveniently synthesized via three steps including nitration, carbamic chlorination, and aminolysis reactions. <span style=font-size:10.0pt;mso-bidi-font-style: italic>The structures of all compounds prepared have been confirmed by 1 H NMR, IR spectroscopy and elemental analyses, <span style=font-size:10.0pt;mso-font-kerning: 0pt>and a part has been identified by 13 C NMR <span style=font-size: 10.0pt;mso-bidi-font-style:italic>. The preliminary bioassay indicates that some of the target compounds possesses moderate herbicidal activity against Echinochloa crusgalli and Amaranthus albus . However, some of the title compounds presented high plant growth regulating activity against rice. <span style=font-size:11.0pt;mso-fareast-font-family: times= new= roman;mso-font-kerning:0pt=>2. <span style=font-size:11.0pt;mso-font-kerning: 0pt>Keywords: Amino Acid Ethyl Ester; Synthesis × N -Nitro Urea Derivative; Herbicidal Activity

Tandem four-component reaction for efficient synthesis of dihydrothiophene with substituted amino acid ethyl esters.

The one-pot four-component reaction of aromatic aldehydes, malononitrile, 1,3-thiazolidinedione and ethyl glycinate hydrochloride in ethanol in the presence of triethylamine afforded trans-dihydrothiophene ureidoformamide derivatives in moderate to good yields. The other α-amino acid ethyl esters resulted in the corresponding diastereoisomeric dihydrothiophene derivatives with various molecular ratios. The functionalized thiophene derivatives were also successfully prepared by sequential dehydrogenation reaction with DDQ.

The synthesis, structural characterization and biological evaluation of novel N-{para-(ferrocenyl) ethynyl benzoyl} amino acid and dipeptide methyl and ethyl esters as anticancer agents

A series of N-{para-(ferrocenyl) ethynyl benzoyl} amino acid and dipeptide methyl and ethyl esters 4–18 were prepared by coupling para-(ferrocenyl) ethynyl benzoic acid 3 to the amino acids GABA(OMe), GABA(OEt) and the dipeptide esters GlyGly(OMe), GlyGly(OEt), Gly-L-Ala(OMe), Gly-L-Ala(OEt), Gly-D-Ala(OMe), Gly-D-Ala(OEt), Gly-L-Leu(OEt), Gly-L-Phe(OEt), SarGly(OMe), SarGly(OEt), Sar-L-Ala(OEt), L-ProGly(OEt) and L-Pro-L-Ala(OEt) using the standard N-(3-dimethylaminopropyl)-N’-ethylcarbodiimide hydrochloride (EDC), 1-hydroxybenzotriazole (HOBt) protocol. All the compounds were fully characterized using a combination of I.R., UV-Vis, 1H NMR, 13C NMR, DEPT-135, 1H-13C COSY (HMQC) spectroscopy and electrospray ionization mass spectrometry (ESI-MS). Selected compounds 5, 7, 9, 11, 16, 17 and 18 showed micromolar activity in the H1299 NSCLC cell line, with IC50 values in the range of 3.8–8.3 μM.

Diastereoselective synthesis of 1,3-di- and 1,3,3-trisubstituted diaziridines coupled with neurotransmitter amino acids

The pH-controlled one-pot three-component condensation of carbonyl compounds, amino acid ethyl esters and hydroxylamine-O-sulfonic acid in water–ethanol mixture at 0–5 ̊C diastereoselectively affords conjugates of 1,3-di- or 1,3,3-trisubstituted diaziridines with neurotransmitter amino acids.

Effect of Hydrophobic Side Chains in the Induction of Immune Responses by Nanoparticle Adjuvants Consisting of Amphiphilic Poly(γ-glutamic acid).

The new generation vaccines are safe but poorly immunogenic, and thus they require the use of adjuvants. Adjuvants that can control the balance and induction level of cellular and humoral immunities are urgently required for the treatment of and/or protection from infectious diseases and cancers. However, there are no adjuvants which can achieve these requirements. In this study, amphiphilic poly(γ-glutamic acid) (γ-PGA) with various kinds of hydrophobic amino acid ethyl esters (AAE) was synthesized (γ-PGA-AAE) and used to prepare antigen-encapsulated nanoparticles (NPs). γ-PGA-graft-Leu (γ-PGA-Leu, where Leu = leucine ethyl ester), γ-PGA-graft-Phe (γ-PGA-Phe, where Phe = phenylalanine ethyl ester), and γ-PGA-graft-Trp (γ-PGA-Trp, where Trp = tryptophan ethyl ester) formed monodispersed NPs that encapsulated ovalbumin (OVA). The type and the induction level of the antigen-specific cellular and humoral immunities could be controlled by the kinds of hydrophobic segments and vaccine formulation (encapsulation or mixture) used. When OVA was encapsulated into NPs, the cellular immunity was dominantly induced, while humoral immunity was dominant when OVA was mixed with NPs. These results are a first report to demonstrate that the balance and induction level of cellular and humoral immunities could be controlled by modifying compositions of NPs and vaccine formulation. Our results suggest that γ-PGA-AAE NPs can provide safe and efficient nanoparticle-based vaccine adjuvants, and the results also provide guidelines in the rational design of amphiphilic polymers as vaccine adjuvants which can control the balance of immune responses.

Absolute Configurational Assignments of Amino Acid Esters by a CD‐Sensitive Malonamide‐Linked Zinc Bisporphyrinate Host

AbstractA novel malonamide‐linked zinc bisporphyrinate [Zn2‐1] has been designed and synthesized. UV‐vis and NMR spectroscopic studies suggest the molecule aggregates in solution. Such zinc bisporphyrinate is very CD‐sensitive when it is mixed with amino acid ethyl esters. The amplitude value of the induced circular dichroism (ICD) is up to ca. 1500 L·mol−1·cm−1. Further studies by 1H NMR and UV‐vis spectroscopies reveal amino acid esters function as monodentate ligands, and [Zn2‐1] interacts with amino acid ethyl esters through coordination and hydrogen bonding interactions.

Chemo-enzymatic routes to lipopeptides and their colloidal properties.

A unique chemo-enzymatic route to lipopeptides was demonstrated herein that, relative to alternative methods such as solid-phase peptide synthesis (SPPS) and microbial synthesis, is simple, efficient, and scalable. Homo- and co-oligopeptides were synthesized from amino acid ethyl esters via protease catalysis in an aqueous media, followed by chemical coupling to fatty acids to generate a library of lipopeptides. Synthesized lipopeptides were built from hydrophobic moieties with chain lengths ranging from 8 to 18 and peptides consisting of oligo(L-Glu) or oligo(L-Glu-co-L-Leu) with an average of seven to eight repeating units. The chemical structures of the lipopeptides were characterized and confirmed by NMR and matrix-assisted laser desorption/ionization (MALDI). The colloidal and interfacial properties of these lipopeptides were characterized and compared in terms of the hydrophobic chain length, oligopeptide composition, and solution pH. The results showed correlation between the interfacial activity of the lipopeptides and the hydrophobicity of the fatty acid and oligopeptide headgroup, the effects of which have been semiquantitatively described in the manuscript. Results from these studies provide insights into design principles that can be further expanded in future work to access lipopeptides from protease-catalysis with improved control over sequence and exploring a wider range of peptide and lipid compositions to further tune lipopeptide biochemical and physical properties.

M-Phthalic Diamide-Linked Zinc Bisporphyrinate: Spontaneous Resolution of Its Crystals and Its Application in Chiral Recognition of Amino Acid Esters

A novel m-phthalic diamide-linked zinc bisporphyrinate [Zn2-1] has been designed and synthesized. Its chiral crystalline samples have been spontaneously resolved by crystallization. Data for C48H29N5OZn follow: tetragonal, I41, a = 17.809(2) Å, b = 17.809(2) Å, c = 27.080(8) Å, V = 8589 (3) Å(3), Z = 8. X-ray crystallography reveals the two porphyrin subunits are clockwise arranged in the solved structure. Each zinc atom is coordinated by four pyrrole nitrogens and the amide oxygen of the neighboring molecule. Through coordination bonds, it forms a helical chain with P configuration along the c axis. The overall crystal forms an unprecedented chiral bisporphyin coordination polymer. The chirality of the single crystals has been confirmed by CD spectroscopy. UV-vis and NMR spectroscopic studies suggested the molecule aggregates in solution. Such m-phthalic diamide-linked zinc bisporphyrinate shows a strong chiral recognition ability for amino acid ethyl esters. The amplitude value of the induced circular dichroism (ICD) (∼1900 cm(-1) M(-1)) is around 10 times larger than the one observed for the oxalic amide-linked species (Dalton Trans. 2013, 42, 7651-7659). Further studies by (1)H NMR and UV-vis spectroscopies have revealed amino acid esters function as monodentate ligands, and [Zn2-1] interacts with amino acid ethyl esters through coordination and hydrogen bonding interactions. The CD amplitude values have also shown dependence on the bulkiness of the side chain of amino acid esters. A possible chiral recognition mechanism has been proposed.

Chiral recognition of amino acid esters by a novel oxalic amide-linked bisporphyrin

A novel oxalic amide-linked bisporphyrinate 1has been designed and synthesized, which shows chiral recognition ability for amino acid ethyl esters. The structure of complex 1·(D-Phe-OEt)(L-Phe-OEt) has been solved by X-ray crystallography. It reveals the following information: bisporphyrin unit adopts anti-configuration; compound 1forms 1: 2 complex with amino acid ethyl esters; one important hydrogen bond is formed between the coordinated nitrogen of amino acid ester and carbonyl oxygen in the amide group. The chiral recognition mechanism has been further investigated by UV-Vis spectra, (1)H NMR and DFT/TDDFT calculations.