Aminolysis Of Esters Research Articles

Synthesis, physico-chemical properties and complexing abilities of new amphiphilic ligands from d-galacturonic acid

This paper describes a convenient and efficient synthesis of new complexing surfactants from d-galacturonic acid and n-octanol as renewable raw materials in a two-step sequence. In the first step, simultaneous O-glycosidation–esterification under Fischer conditions was achieved. The anomeric ratio of the products was studied based on the main experimental parameters and the activation mode (thermal or microwave). In the second step, aminolysis of the n-octyl ester was achieved with various functionalized primary amines under standard thermal or microwave activation. The physico-chemical properties of these new amphiphilic ligands were measured and these compounds were found to exhibit interesting surface properties. Complexing abilities of one uronamide ligand functionalized with a pyridine moiety toward Cu(II) ions was investigated in solution by EPR titrations. A solid compound was also synthesized and characterized, its relative structure was deduced from spectroscopic data.

The transition state for peptide bond formation reveals the ribosome as a water trap

Recent progress in elucidating the peptide bond formation process on the ribosome has led to notion of a proton shuttle mechanism where the 2'-hydroxyl group of the P-site tRNA plays a key role in mediating proton transfer between the nucleophile and leaving group, whereas ribosomal groups do not actively participate in the reaction. Despite these advances, the detailed nature of the transition state for peptidyl transfer and the role of several trapped water molecules in the peptidyl transferase center remain major open questions. Here, we employ high-level quantum chemical ab initio calculations to locate and characterize global transition states for the reaction, described by a molecular model encompassing all the key elements of the reaction center. The calculated activation enthalpy as well as structures are in excellent agreement with experimental data and point to feasibility of an eight-membered "double proton shuttle" mechanism in which an auxiliary water molecule, observed both in computer simulations and crystal structures, actively participates. A second conserved water molecule is found to be of key importance for stabilizing developing negative charge on the substrate oxyanion and its presence is catalytically favorable both in terms of activation enthalpy and entropy. Transition states calculated both for six- and eight-membered mechanisms are invariably late and do not involve significant charge development on the attacking amino group. Predicted kinetic isotope effects consistent with this picture are similar to those observed for uncatalyzed ester aminolysis reactions in solution.

Theoretical study on the aminolysis of ester catalyzed by TBD: Hydrogen bonding or covalent bonding of the catalyst?

In this work, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD)-catalyzed aminolysis reaction of methyl acetate with methylamine has been investigated at the B3LYP/6-311++G(d,p) and MP2/6-311++G(d,p) levels of theory. In our calculations, we take into account three possible pathways for the reaction. Path 1 is a ‘full concerted’ mechanism via a S N2-like O → N acyl-transfer transition state through the hydrogen bonding of TBD; Path 2 is a stepwise mechanism involving the tetrahedral intermediates through the hydrogen bonding of TBD; and Path 3 is also a stepwise mechanism including the nucleophilic attack of TBD upon ester with covalently bonding of TBD. Results indicate that Path 2 is the likely mechanism and that the hydrogen bonding of TBD has an important role in the aminolysis of ester. The role of the TBD catalyst is to facilitate the proton transfer and accelerate the reaction.

Synthesis of chiral 1,4-disubstituted-1,2,3-triazole derivatives from amino acids.

A versatile method for the synthesis of chiral 1,4-disubstituted-1,2,3-triazole derivatives starting from easily accessible naturally occurring D-or L-amino acids as chiral synthons is described. The amino acids were converted into azido alcohols, followed by copper catalyzed [3+2] cycloaddition reactions between the azido alcohols and methyl propiolate and subsequent ester aminolysis with primary and secondary amines furnished the target compounds, which were obtained in excellent yields with no racemization. Docking of selected target compounds shows that the chiral 1,4-disubstituted-1,2,3-triazoles derivatives has the potential of mimicking the binding mode of known purine analogues.

β-Keto ester aminolysis of pheophorbide a methyl ester: a facile route for asymmetric chlorin ring substitution

A chemoselective aminolysis of the β-keto ester of pheophorbide a methyl ester is demonstrated opening a facile access to an asymmetric amide functionalization of a chlorin ring using a range of aromatic and aliphatic, primary and secondary amine nucleophiles. Aminolysis of pheophorbide a methyl ester with trans-1,2-diaminocyclohexane is shown to give a symmetric open face chlorin dimer.

Aminolysis of 3-Phenyl Propylthiol Esters Leading to Diverse Sets of Amides

3-Phenyl propylthiol esters were investigated as “activatable” solution phase linkers. These linkers can be activated with silver salts and upon treatment with amines can be converted to the corresponding amides. Under unactivated conditions, the linker is stable to a variety of reagents and reaction conditions including treatment with amines.

Phosphine-Free Synthesis of High-Quality CdSe Nanocrystals in Noncoordination Solvents: “Activating Agent” and “Nucleating Agent” Controlled Nucleation and Growth

CdSe nanocrystals (NCs) are prepared in noncoordination solvents (1-octadecene (ODE) and paraffin liquid) with long-chain primary alkylamine as the sole ligand, ODE-Se, and cadmium fatty acid salt as precursors. The obtained NCs meet the four fundamental parameters for high-quality NCs: high crystallinity, narrow size distribution, moderate photoluminescence quantum yield, and broad range size tunableness. Further, by simply regulating the relative molar ratio of alkylamine to cadmium precursor, the regular sized “nuclei” and final obtained NCs can be produced predictably within a certain size range. The size distribution of regular sized “nuclei” is very narrow (fwhm = 23 ± 1 nm), and the following focusing growth procedure vanishes. This indicates a different nucleation and growth kinetics from that of the well-established “focusing” and “defocusing” theory. By analyzing the conversion factor of precursors and the concentration of magic sized nanoclusters and regular sized “nuclei”, a subtle secondary nucleation mechanism, “quantized fusion”, was proposed. First, magic sized nanoclusters are formed as the critical nuclei; second, quantized critical nuclei will couple together and fuse into perfect regular sized “nuclei” by combining with stoichiometric monomers. The “quantized fusion” transformation could be regulated by the nature and ratios of the “activating agent” and the “nucleating agent”. These transition processes are very rapid and should be kinetically controlled. The molecular mechanism for monomer formation may be based on the traditional ester aminolysis reaction.

Acyl Transfer Catalysis with 1,2,4-Triazole Anion

1,2,4-Triazole anion has been identified as an active acyl transfer catalyst suitable for the aminolysis and transesterification of esters.

Activation of the hydrolytic polymerization of ε-caprolactam by ester functions: Straightforward route to aliphatic polyesteramides

The hydrolytic polymerization of ε-caprolactam (CLa) was carried out in bulk (in absence of solvent) at 250 °C in the presence of carboxylic esters and aqueous H 3PO 2. It turned out that by conducting the ring opening polymerization (ROP) of CLa in the presence of PEO–C(O)–O–C 5H 11, a selected model ester (PEO = poly(ethylene oxide)), a remarkable activating effect of the ester function on the hydrolytic polymerization of the lactam was observed yielding PEO– b–PCLa diblock copolymers. The comparison of the CLa monomer conversions obtained with or without the model ester activated by H 3PO 2, as determined by 1H NMR spectroscopy, has enabled to propose a multi-step mechanism in which three major reactions occurred: (i) ester and lactam hydrolysis, (ii) aminolysis of the carboxylic ester by the resulting primary amine of the hydrolyzed/opened lactam ring and (iii) condensation reactions between carboxylic acids and both amine/hydroxyl functions. The overall result of this multi-step mechanism can be assimilated as an “insertion” of the opened lactam into the ester function. By conducting the hydrolytic polymerization of CLa in the presence of an aliphatic polyester chain, such as poly(ε-caprolactone) (PCLo), polyesteramides were recovered with high yields and random distributions of the CLa and CLo repetitive units as determined by 13C NMR.

Predicting Reactivities of Organic Molecules. Theoretical and Experimental Studies on the Aminolysis of Phenyl Acetates

The quality of reactivity predictions coming from alternative theoretical approaches as well as experimental reactivity constants is examined in the case of the ester aminolysis process. The aminolysis of a series of para-substituted phenyl acetates is studied. The barrier heights for the rate-determining stage of the aminolysis of 16 phenyl acetate derivatives were predicted by employing density functional theory at the B3LYP/6-31+G(d,p) level. Experimental kinetic studies were carried out for the n-butylaminolysis of seven p-substituted phenyl acetates in acetonitrile. The results show that the electrostatic potential at the carbon atom of the carbonyl reaction center provides an excellent description of reactivities with regard to both theoretical barrier heights and experimental rate constants. The performance of other reactivity indices, Mulliken and NBO atomic charges, electrophilicity index, and Hammett constants, is also assessed.

Lipase-catalyzed chemoselective aminolysis of various aminoalcohols with fatty acids

Candida antarctica lipase is well known to convert amines and alcohols into amides and esters. This report describes the development of a solvent-free enzymatic process for the production of fatty alkanolamides. The aminolysis of linoleyl ethyl ester with several aminoalcohols from C2 to C6 (linear or branched compounds), and the very high selectivity of amide compounds have been observed. Our investigation leads us to develop an original biotechnological process for the chemoselective synthesis of new active molecules for cutaneous application.

Synthesis and corrosion inhibition of α-amino acids alkylamides for mild steel in acidic environment

New compounds of alkylamides derived from α-amino acids were tested as corrosion inhibitors for carbon steel in an aqueous solution of hydrochloric acid. The chemical synthesis of these amides performed by aminolysis of α-amino acid methyl esters resulted in good yields. Electrochemical testing was carried out using polarization scans and weight loss measurements. Polarization scans indicated that compounds act as mixed corrosion inhibitors with an efficiency of 80–90% when dissolved in the testing solution at ≥50 ppm, whereas gravimetric results displayed a similar tendency. Microtox testing indicated a correlation with the molecular structure of inhibitors. Apparently, a long aliphatic chain (C > 12) promoted not only higher corrosion efficiency, but also a higher toxicity. The higher efficiency of dodecyl amine of tyrosine was apparently derived from its longer aliphatic chain, with some contribution from its phenyl ring, which reinforces the molecular interactions of π type bonding to the d orbital metal favouring film formation.

One-Pot Synthesis of Quinoline-Based Tetracycles by a Tandem Three-Component Reaction

A practical one-pot synthetic strategy for the efficient synthesis of a range of structurally interesting and bioactive quinoline-based tetracycles has been developed. A key step in the synthesis is a tandem three-component reaction of heteroaromatic amine, methyl 2-formylbenzoate and (t)butyl isonitrile, followed by TFA-mediated lactamization via intramolecular aminolysis of an adjacent ester. Results related to a kinase-panel screening for several selected compounds are also discussed in this article.

Unambiguous Evidence for Efficient Chemical Catalysis of Adenosine Ester Aminolysis by Its 2‘/3‘-OH

Intramolecular aminolysis reactions, catalyzed by a vicinal OH group, were studied computationally as model reactions of ribosome-catalyzed intracomplex aminolysis. The results predicts 2−6-fold higher enthalpic than entropic contribution to the reduction of the activation free energy, caused by the combined proximity effect of the attacking syn-NH2 group and the catalytic syn-OH group. The acceleration predicted by the theory is supported by the observed instantaneous lactamization of ornithinyl adenosine as compared to the much slower lactamization of ornithinyl 2‘-deoxyadenosine. This observation is the first unambiguous experimental demonstration of chemical catalysis of the 1,2-diol monoester aminolysis by its vicinal 2-OH groupthe reaction naturally catalyzed by ribosome.

Parallel Synthesis of an Amide Library Based on the 6,8-Dioxa-3-azabicyclo[3.2.1]octane Scaffold by Direct Aminolysis of Methyl Esters

An efficient synthesis of unsubstituted and substituted amides based on the 6,8-dioxa-3-azabicyclo[3.2.1]octane scaffold is described. The reaction, carried out at 60 degrees C in the absence of solvent, is characterized by its mildness and ease of workup. A library of amides, was synthesized by combination of methyl esters 1-6 with various amines. In addition, the microwave-assisted automated synthesis of the library was compared with the above conventional parallel synthesis. Microwave synthesis significantly decreased the reaction time from hours to minutes.

A convenient aminolysis of esters catalyzed by 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) under solvent-free conditions

Aminolysis of esters by using the organocatalyst 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is reported. Secondary and tertiary amides were synthesized from alkyl or aryl esters with a variety of primary and secondary amines in good to excellent yields (60–94%) under solvent-free conditions (SFC).

Aminolysis of Allyl Esters with Bislithium Aryl Amides.

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Aminolysis of allyl esters with bislithium aryl amides

The aminolysis of allyl esters with bislithium amides is reported. Tertiary aryl amides were synthesized in a one-pot reaction with bislithium amides and a suitable electrophile in good yields. The scope of this reaction was demonstrated with a variety of anilines and aminopyridines and applied to the synthesis of triphenylmethylacetamides.

DFT studies on the structure and stability of zwitterionic tetrahedral intermediate in the aminolysis of esters

The structure and stability of putative zwitterionic complexes in the aminolysis of phenyl acetate with ammonia are examined using density functional and ab initio methods by applying the explicit, up to 7 H 2O, and implicit, PCM, solvation models. The stability of the zwitterionic tetrahedral intermediate required an explicit solvation by at least five water molecules with stabilization energy of approximately 35 kcal mol −1. The explicit water molecules are inter-connected by cyclic hydrogen bonding networks terminating at the negatively charged carbonyl oxygen and one of the hydrogen atoms on the positively charged ammonium ion.

Ester aminolysis by morpholine in AOT-based water-in-oil microemulsions

A kinetic study of the aminolysis of p-nitrophenyl acetate (NPA) by morpholine (MOR) in AOT/isooctane/water (w/o) microemulsions was conducted. Based on the solubilities of NPA and MOR in water and isooctane, both compounds partition between the continuous medium, interface and water microdroplets of the microemulsion. Because the rate of the aminolysis reaction decreases with decreasing polarity of the solvent, the reaction must take place to a negligible extent in the continuous medium relative to the interface and the aqueous microdroplets. We used the pseudo-phase model to determine the rate constants at the interface, k 2 i , and in the water microdroplets, k 2 w . Both k 2 i and k 2 w were found to be independent of W in the aminolysis of NPA by MOR. This is a result of the expected increase in k 2 w on decreasing W being offset by the decrease in k 2 i with increase in the water content of the system. Based on the results, the reaction takes place to an extent of only 16% in the water microdroplets at W = 40 , the proportion decreasing with decreasing water content.