Acyl Transfer Reactions Research Articles

ChemInform Abstract: A Novel Synthetic Approach to Benzo[h]chromones via Sequential Intramolecular Alkynoyl Transfer Followed by 6-endo Ring Closure.

Abstract An intramolecular acyl transfer reaction took place on treatment of 1-methoxymethoxy-3-(2-alkynoyloxy)methyl-2-iodonaphthalenes with n-BuLi at −78°C to give 1-methoxymethoxy-2-alkynoyl-3-hydroxymethylnaphthalenes in high yields. After protection of the hydroxymethyl group as benzoates, formation of a γ-pyrone ring was easily achieved by deprotection of the MOM group followed by spontaneous 6-endo-digonal ring closure under mild acidic conditions.

Do changes in transglutaminase activity alter latent transforming growth factor beta activation in experimental diabetic nephropathy?

Diabetic nephropathy is the leading cause of end-stage kidney failure worldwide. It is characterized by excessive extracellular matrix accumulation. Transforming growth factor beta 1 (TGF-β1) is a fibrogenic cytokine playing a major role in the healing process and scarring by regulating extracellular matrix turnover, cell proliferation and epithelial mesanchymal transdifferentiation. Newly synthesized TGF-β is released as a latent, biologically inactive complex. The cross-linking of the large latent TGF-β to the extracellular matrix by transglutaminase 2 (TG2) is one of the key mechanisms of recruitment and activation of this cytokine. TG2 is an enzyme catalyzing an acyl transfer reaction leading to the formation of a stable ε(γ-glutamyl)-lysine cross-link between peptides. To investigate if changes in TG activity can modulate TGF-β1 activation, we used the mink lung cell bioassay to assess TGF-β activity in the streptozotocin model of diabetic nephropathy treated with TG inhibitor NTU281 and in TG2 overexpressing opossum kidney (OK) proximal tubular epithelial cells. Application of the site-directed TG inhibitor NTU281 caused a 25% reduction in kidney levels of active TGF-β1. Specific upregulation of TG2 in OK proximal tubular epithelial cells increased latent TGF-β recruitment and activation by 20.7% and 19.7%, respectively, in co-cultures with latent TGF-β binding protein producing fibroblasts. Regulation of TG2 directly influences the level of active TGF-β1, and thus, TG inhibition may exert a renoprotective effect by targeting not only a direct extracellular matrix deposition but also TGF-β1 activation and recruitment.

Structure dependence in the solvolysis kinetics of amino acid esters

Abstract To better understand acyl transfer reactions of oligopeptides, seventeen N -acyl amino acid esters were solvolyzed in mildly basic methanol- d 4 . All show pseudo-first-order kinetics by 1 H NMR. The rate constant varies up to 400-fold with the identity of the amino acid and up to 6200-fold with the identity of the N -acyl group. The impact of the N -acyl group on the rate constant is discussed in terms of crowding, amide conformation, and amide C O bond character.

Transglutaminase를 생산하는 Streptomyces platensis의 분자생물학적인 연구를 위한 접합 전달법 확립

식품단백질의 물성과 기능성을 개선시켜 산업적인 가치가 매우 높은 TGase를 생산하는 S. platensis YK-2의 분자 유전학적인 연구를 위해 형질전환방법을 확립하였으며 본 연구를 위해 도입된 방법은 대장균을 plasmid DNA의 공여체로, S. platensis의 포자를 수용체로 사용하는 접합전달법이다. S. platensis를 위한 최적 접합전달조건은 50 mM의 <TEX>$MgCl_2$</TEX>를 첨가한 MS배지에 열처리를 하지 않은 포자와 <TEX>$5{\times}10^7$</TEX>의 plasmid DNA 공여체인 E. coli를 사용하는 것이다. 또 본 연구를 통해 얻어진 접합전달체의 attB site에 대한 분석을 통해 S. platensis chromosome의 pirin 상동체를 코드하는 ORF내에 attB site가 단일위치로 존재하고 있으며 이미 밝혀진 다른 방선균유래 attB site의 염기서열에 대해 77.8%~96.3%의 상동성을 나타냈다. Streptomyces platensis YK-2, newly isolated from forest soil, produces transglutaminase (TGase), which catalyses an acyl transfer reaction between the primary grade amine and protein or <TEX>$\gamma$</TEX>-carboxyamide group of peptide bound glutamine residues. For a molecular genetic study of S. platensis, an effective transformation method was established by using a conjugal transfer of DNA from Escherichia coli to spores of actinomycetes. The highest transconjugation frequency of S. platensis was obtained on an MS medium containing 50 mM <TEX>$MgCl_2$</TEX>, using <TEX>$5{\times}10^7\;E$</TEX>. coli as a DNA donor and <TEX>$1{\times}10^8$</TEX> spores without heat treatment as a host. We also identified that S. platensis contains a single attB site within an ORF encoding a pirin-homolog, and that its attB site sequence shows high homology to that of S. logisporoflavus. In addition, it was confirmed by phenotypic analyses of exconjugants that the introduction of heterologous DNA into the attB site of the S. platensis chromosome does not affect its morphological differentiation and TGase production.

ChemInform Abstract: Organocatalysis with Azahelicenes: The First Use of Helically Chiral Pyridine‐Based Catalysts in the Asymmetric Acyl Transfer Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Substituent effects in nucleophiles on activation parameters in the bimolecular nucleophilic reactions in solution

Changes of the activation parameters, ΔH‡ and ΔS‡, in the SN2, SNV, AdN, SNAr and acyl-transfer reactions with phenol, aniline and pyridine nucleophiles in various solvents were correlated with σ constants of the substituents in the aromatic ring of the nucleophiles. The resultant δΔH‡ and δΔS‡ reaction constants are linearly related for variations of substituents at the nucleophile. Correlation of δΔH‡vs. δΔS‡ allow the estimation of the contribution of changes of the internal enthalpy, δΔH‡int, to the enthalpy reaction constant, δΔH‡, which gives a single linear dependence on the Hammett ρ reaction constants for all bimolecular nucleophilic reactions. The deviations from dependence of δΔH‡intvs. ρ can be interpreted in terms of changes of the transition state structure or reaction mechanism. The results obtained show that the substituent effects in the nucleophiles on the charge development in the transition state are governed by the magnitude of δΔH‡int.

Native chemical ligation with Nα acyl transfer auxiliaries

Native chemical ligation (NCL) is a simple procedure that enables synthetic access to many proteins and is increasingly harnessed to study protein structure and function. However, the generality of this method is limited by the requirement for cysteine residues suitably positioned throughout the target protein. Auxiliary approaches have been developed to overcome this limitation, wherein a removable group is introduced at the amino terminus of a peptide conveying ligation properties comparable to cysteine. Present auxiliary approaches combine the thioester exchange concept applied first in NCL with a number of acyl transfer reactions first systematically explored by Kemp and coworkers. The current methods for auxiliary mediated ligation appear promising for the synthesis of proteins and in particular post-translational modified proteins.

Helical self-assembly of molecules in pseudopolymorphs of racemic 2,6-di-O-(4-halobenzoyl)-myo-inositol 1,3,5-orthoformates: clues for the construction of molecular assemblies for intermolecular acyl transfer reaction

The crystal structure of racemic 2,6-di-O-benzoyl-myo-inositol 1,3,5-orthoformate (1) which underwent a facile intermolecular benzoyl transfer reaction in the solid state, revealed a helical assembly of molecules along the two-fold screw axis via O–H⋯O hydrogen bond bringing the electrophile (CO) and the nucleophile (–OH) in close proximity along the helical axis. However, structurally related racemic 2,6-di-O-(p-halobenzoyl)-myo-inositol 1,3,5-orthoformates (bromo (2) and chloro (3)) produced triclinic dimorphs (both P) when crystallized from methanol and ethyl acetate. Molecules in either form did not assemble spirally (like 1), and instead exhibited a one-dimensional isostructurality, bridging O–H⋯O linked identical molecular strings via C–H⋯O interactions across the inversion center. However, the molecules of 2 and 3 assembled in a helical manner similar to 1 with inclusion of solvent molecules in the crystal lattice when crystallized from other common organic solvents. Remarkably, in all the solvates the host molecules formed strikingly similar helices around the crystallographic 21-screw axis through O–H⋯O bond involving the –OH group and carbonyl oxygen of the equatorial C2-O-benzoyl group. Comparison of the crystal structure of dimorphs and the solvatomorphs revealed that the solvent molecules, which interact with the orthoformate-bridge, trigger the helix formation of the host. The difference in the crystal structures of solvatomorphs arises in the interlinking of the neighbouring helices, which creates voids of different sizes to accommodate the solvent molecules. All the solvates crystallized in the monoclinic system distributed over three different space groups P21/n, P21/c and C2/c. In the P21/n system, the adjacent helices are linked via C–X⋯O contacts, in P21/c via C–H⋯X (X = Cl, Br) contacts and in C2/c via short X⋯X contacts (X = Cl). The helical organization achieved through solvent mediation and inclusion is of significance in creating molecular packing for intermolecular acyl transfer reactions in crystals.

Microwave‐assisted derivatization of cellulose in an ionic liquid: An efficient, expedient synthesis of simple and mixed carboxylic esters

AbstractMicrowave (MW)‐assisted cellulose dissolution in ionic liquids (ILs) has routinely led either to incomplete biopolymer solubilization, or its degradation. We show that these problems can be avoided by use of low‐energy MW heating, coupled with efficient stirring. Dissolution of microcrystalline cellulose in the IL 1‐allyl‐3‐methylimidazolium chloride has been achieved without changing its degree of polymerization; regenerated cellulose showed pronounced changes in its index of crystallinity, surface area, and morphology. MW‐assisted functionalization of MCC by ethanoic, propanoic, butanoic, pentanoic, and hexanoic anhydrides has been studied. Compared with conventional heating, MW irradiation has resulted in considerable decrease in dissolution and reaction times. The value of the degree of substitution (DS) was found to be DSethanoate &gt; DSpropanoate &gt; DSbutanoate. The values of DSpentanoate and DShexanoate were found to be slightly higher than DSethanoate. This surprising dependence on the chain length of the acylating agent has been reported before, but not rationalized. On the basis of the rate constants and activation parameters of the hydrolysis of ethanoic, butanoic, and hexanoic anhydrides in aqueous acetonitrile (a model acyl transfer reaction), we suggest that this result may be attributed to the balance between two opposing effects, namely, steric crowding and (cooperative) hydrophobic interactions between the anhydride and the cellulosic surface, whose lipophilicity has increased, due to its partial acylation. Four ethanoate‐based mixed esters were synthesized by the reaction with a mixture of the two anhydrides; the ethanoate moiety predominated in all products. The DS is reproducible and the IL is easily recycled. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 48: 134–143, 2010

Lipase resolution of new (±)-3-aryloxy-1-halogenopropan-2-ols: Versatile building blocks for β-adrenergic receptor antagonists

Using two commercial immobilized lipases Lipozyme ® TL and Novozym ® 435 effective kinetic resolution of several novel 3-aryloxy-1-halogenopropan-2-ols was achieved by acyl transfer reaction in organic solvents, yielding both enantiomers with 89–99% ee. In preparative resolutions carried out in tert-butyl methyl ether at 25 °C with vinyl acetate as acyl donor enantioselectivity ratio E was from 64 to 99. The resolved enantiomers were successfully used as chiral building blocks in the synthesis of new 1-alkylamino-3-aryloxypropan-2-ols, by nucleophilic halogen substitution with isopropylamine and tert-butylamine. The obtained products will be evaluated in vitro as potential new β-adrenergic receptors antagonists.

FLAG-tag selective covalent protein labeling via a binding-induced acyl-transfer reaction

A FLAG tag selective protein labeling method is newly developed in this study. Coupling of the selective binding between synthetic Ni-complex probe and FLAG tag with the acyl transfer reaction enables the site-selective covalent modification of FLAG peptide and FLAG-tag fused protein.

Antibacterial Functionalization of Wool via mTGase-Catalyzed Grafting of ε-Poly-l-lysine

epsilon-Poly-L-lysine (epsilon-PL), a natural biomacromolecule having a broad spectrum of antibacterial activity, was grafted on the wool fiber via the acyl transfer reaction catalyzed by microbial transglutaminase (mTGase) to develop a new strategy for antibacterial functionalization of proteinous materials. The effects of the concentrations of epsilon-PLs and mTGases on the graft yields were investigated. A coating of epsilon-PL that almost completely covered the scale profile on the wool surface was visualized by scanning electron microscopy (SEM) and further demonstrated in terms of Allwörden's reaction characteristic of wool. Identifiable differences in lysine content and color depth among the stained wool samples reveal the changes in the surface composition and polarity caused by the incorporation of epsilon-PL onto the wool substrate, respectively. The ratio of bacteriostasis to Escherichia coli of the wool fabric grafting epsilon-PL reached 96.6 %, indicating an excellent antibacterial effect. The application of epsilon-PL and corresponding mTGase-catalyzed grafting reaction would provide a worthwhile reference for antibacterial functionalization of proteinous materials in various forms.

ChemInform Abstract: Synthesis of Secondary α‐Perfluoroalkyl‐ and Tertiary α,α‐Bis(perfluoroalkyl)‐N‐methylprolinols and Their Catalytic Activities in the Acyl Transfer Reaction.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Relative nucleophilic reactivity of pyridines and pyridine N-oxides (supernucleophilicity of pyridine N-oxides)

Supernucleophilicity of pyridine N-oxides in acyl transfer reactions was rationalized for the first time on a theoretical level. Unlike pyridines, transition state derived from pyridine N-oxides is stabilized by direct conjugation between the nucleophilic and electrophilic components.

A Catalytically Active, Permanently Microporous MOF with Metalloporphyrin Struts

Through the use of the tetratopic ligand 1,2,4,5-tetrakis(4-carboxyphenyl)benzene as a key building block, a permanently microporous metal-organic framework with Lewis acidic (porphyrin)Zn struts, ZnPO-MOF, can be made in high yields. ZnPO-MOF can efficiently catalyze acyl-transfer reactions primarily by preconcentrating the substrates within its pores, in stark contrast to analogous supramolecular systems.

Effect of Microbial Transglutaminase on Dough Proteins of Hard and Soft (Triticum aestivium) and Durum (Triticum durum) Wheat Cultivars

ABSTRACTMicrobial transglutaminase (MTGase), a protein‐glutamine γ‐glutamyl transferase (E.C. 2.3.2.13), catalyzes acyl transfer reactions by introducing a covalent cross‐link between l‐lysine and l‐glutamine residues. The use of this enzyme has been proposed as an improver to increase dough strength. The objective of this study was to assess and compare the effect of MTGase on different fractions of dough proteins found in hard, soft, and durum wheat. Three different concentrations of the MTGase (0, 5, and 10U/g of gluten) were tested. Moisture, protein, and dry gluten contents were determined for each concentration in addition to rheological measurements done with the farinograph. Following each treatment, the dough proteins were extracted and analyzed by SE‐HPLC and RP‐HPLC. Soluble polymeric protein, gliadins, albumins, and globulins were quantified in addition to the gliadin subclasses and glutenin subunit types. The combustion procedure was used to determine the amount of insoluble polymeric protein. Differences were observed in susceptibility to MTGase catalysis among the dough proteins of the cultivars studied: the cultivar Cortazar (soft wheat) was the most susceptible. The proteins of this cultivar had a characteristically higher amount of ω and α+β gliadins when compared with the other cultivars. As reported earlier, solubility of high molecular weight glutenin subunits and ω‐gliadins was reduced because of the MTGase treatment. However, all gliadin subclasses, including the γ and α+β gliadins, also participated in cross‐linking. The proteins of the cultivar Altar (durum wheat) were the least susceptible to the effects of MTGase. Albumins and globulins did not show any reduction in solubility, implying that they did not participate in cross‐linking.

Synthesis of secondary α-perfluoroalkyl- and tertiary α,α-bis(perfluoroalkyl)- N-methylprolinols and their catalytic activities in the acyl transfer reaction

Various chiral α-perfluoroalkyl- N-methylprolinols were prepared and their organocatalytic activities in an acyl transfer reaction of 4-nitrophenyl 2-methoxyacetate with methanol- d 4 in chloroform- d were examined. As a result, α-trifluoromethyl- N-methylprolinol was a more effective acyl transfer catalyst than not only secondary α-perfluorobutyl- and n-butyl- N-methylprolinols but also tertiary α,α-bis(perfluorobutyl)- N-methylprolinol.

Organocatalysis with azahelicenes: the first use of helically chiral pyridine-based catalysts in the asymmetric acyl transfer reaction

The successful utilisation of a helicene-based organocatalyst in acylative kinetic resolution of racemic secondary alcohol was described. Employing rac-1-phenylethanol, optically pure (–)-(M)-2-aza[6]helicene (5–20 mole %), isobutyric anhydride and N-ethyldiisopropylamine in chloroform at 22–40 °C, an asymmetric acyl transfer reaction took place overwhelming the uncatalysed background process. Moderate reactivity as well as selectivity factor (s = 9, 10) were observed. An effective control of the enantiodiscriminating step in acylative kinetic resolution by the helically chiral organocatalyst was proven for the first time.

The lithiation and acyl transfer reactions of phosphine oxides, sulfides and boranes in the synthesis of cyclopropanes

Phosphine oxides are lithiated much faster than phosphine sulfides and phosphine boranes. Phosphine sulfides are in turn lithiated much more readily than phosphine boranes. It was possible to trap a phosphine sulfide THF in one case which upon treatment with t-BuOK gave cyclopropane, showing that phosphine sulfides readily undergo both phosphinoyl transfer and cyclopropane ring closure just like their phosphine oxide counterparts. The obtained data show that phosphine oxides are easily lithiated and undergo phosphoryl transfer much more readily and faster than phosphine sulfides and phosphine boranes. The observations suggest that it would be possible to perform reactions involving phosphine oxides in the presence of phosphine boranes or phosphine sulfides, potentially allowing regioselective alkylation of phosphine oxides in the presence of phosphine boranes or phosphine sulfides.

Indium(III) Triflate: A Highly Efficient Catalyst for Reactions of Sugars[1

Indium(III) trifluoromethanesulfonate has been found to be extremely efficient in catalyzing acyl transfer reactions of various carbohydrates and their derivatives. Selective acetolyses of certain benzyl ethers/isopropylidene acetals of sugars have been possible using In(OTf)3 in Ac2O (neat). Reaction of the per-O-acetate of 2-deoxy-2-phthalimido-D-glucose with benzyl mercaptan in the presence of In(OTf)3 led to the formation of the corresponding thioglycoside in high yield. Facile formation and hydrolysis of the isopropylidene and benzylidene acetals of various carbohydrates have also been achieved very efficiently in the presence of In(OTf)3. The results show great promise for In(OTf)3 in synthetic carbohydrate chemistry.