Glycolamide Esters Research Articles

Combinatorial Library Screening Coupled to Mass Spectrometry to Identify Valuable Cyclic Peptides

Combinatorial library screening coupled to mass spectrometry (MS) analysis is a practical approach to identify useful peptides. Cyclic peptides can have high biological activity, selectivity, and affinity for target proteins, and high stability against proteolytic degradation. Here we describe two strategies to prepare combinatorial libraries suitable for MS analysis to accelerate the discovery of cyclic peptide structures. Both approaches use ChemMatrix resin and the linker 4-hydroxymethylbenzoic acid. One strategy involves the synthesis of a one-bead-two-peptides library in which each bead contains both the cyclic peptide and its linear counterpart to facilitate MS analysis. The other protocol is based on the synthesis of a cyclic depsipeptide library in which a glycolamidic ester group is incorporated by adding glycolic acid. After library screening, the ring is opened and the peptide is released simultaneously for subsequent MS analysis. © 2016 by John Wiley & Sons, Inc.

A simple protocol for combinatorial cyclic depsipeptide libraries sequencing by matrix-assisted laser desorption/ionisation mass spectrometry.

Short cyclic peptides have a great interest in therapeutic, diagnostic and affinity chromatography applications. The screening of 'one-bead-one-peptide' combinatorial libraries combined with mass spectrometry (MS) is an excellent tool to find peptides with affinity for any target protein. The fragmentation patterns of cyclic peptides are quite more complex than those of their linear counterparts, and the elucidation of the resulting tandem mass spectra is rather more difficult. Here, we propose a simple protocol for combinatorial cyclic libraries synthesis and ring opening before MS analysis. In this strategy, 4-hydroxymethylbenzoic acid, which forms a benzyl ester with the first amino acid, was used as the linker. A glycolamidic ester group was incorporated after the combinatorial positions by adding glycolic acid. The library synthesis protocol consisted in the following: (i) incorporation of Fmoc-Asp[2-phenylisopropyl (OPp)]-OH to Ala-Gly-oxymethylbenzamide-ChemMatrix, (ii) synthesis of the combinatorial library, (iii) assembly of a glycolic acid, (iv) couple of an Ala residue in the N-terminal, (v) removal of OPp, (vi) peptide cyclisation through side chain Asp and N-Ala amino terminus and (vii) removal of side chain protecting groups. In order to simultaneously open the ring and release each peptide, benzyl and glycolamidic esters were cleaved with ammonia. Peptide sequences could be deduced from the tandem mass spectra of each single bead evaluated. The strategy herein proposed is suitable for the preparation of one-bead-one-cyclic depsipeptide libraries that can be easily open for its sequencing by matrix-assisted laser desorption/ionisation MS. It employs techniques and reagents frequently used in a broad range of laboratories without special expertise in organic synthesis.

Prolonged naproxen joint residence time after intra-articular injection of lipophilic solutions comprising a naproxen glycolamide ester prodrug in the rat

Intra-articular injection of oil solutions of lipophilic prodrugs that rapidly degrade to their parent compound in synovial fluid may constitute a feasible approach to increase the joint residence time of non-steroidal anti-inflammatory drugs. In this in vivo study, oil solutions of the N,N-diethyl glycolamide ester prodrug of naproxen (16 mg/ml) were injected into the rat knee joint by dosing 6 μl formulation per 100g body weight. The sustained release properties were compared to those of intra-articularly injected aqueous and oil solutions of naproxen by monitoring the naproxen serum concentrations over time. Two oils, medium-chain triglycerides and castor oil, differing with respect to viscosity were tested. After intra-articular administration of oil prodrug solutions, a significant increase in the time to maximum naproxen serum concentration from around 40 to 245 min, an increase in the MRT(j) from around 0.11 to 3.3h and a 30% reduction in the maximum serum concentration were observed compared to that of the parent naproxen. The similar serum profiles obtained using the two oils indicate that the release was not affected by the oil viscosity. A prolonged naproxen joint residence time in rats was shown by intra-articular injection of an oil prodrug solution.

Nimesulide Based Novel Glycolamide Esters: Their Design, Synthesis, and Pharmacological Evaluation

The nimesulide based novel glycolamide esters were designed and synthesized for the first time via a three‐step method starting from nimesulide. Structures of the synthesized compounds were confirmed by spectroscopic analysis. All the synthesized compounds were examined for their cytotoxic effects in vitro, some of which showed significant cytotoxic activities against HCT‐15 human colon cancer cell line.

Modification of concomitant drug release from oil vehicles using drug–prodrug combinations to achieve sustained balanced analgesia after joint installation

Intra-articular injection of two drugs in a sustained drug delivery system combining the use of lipophilic solution with the prodrug approach may provide efficient and prolonged postoperative pain treatment after arthroscopic procedures. In the present study, the concomitant release of N,N-diethyl glycolamide ester of naproxen and ropivacaine from an oil vehicle consisting of medium-chain triglycerides were investigated in vitro. The release into both phosphate buffer and 80% (v/v) synovial fluid at pH 7.4 was examined in two dialysis membrane-based release models. The ester prodrug exhibited high solubility in medium-chain triglyceride, a high partition coefficient and was rapidly converted to naproxen in synovial fluid. Compared to naproxen, the release of the prodrug from the oil was sustained. In synovial fluid, the reconversion to naproxen resulted in faster release compared to that observed using buffer. In both release models, the use of ropivacaine-prodrug combination provided concomitant release from the oil into synovial fluid with ropivacaine being released faster than naproxen. The use of lipophilic prodrugs that are converted fast to the parent drug in synovial fluid seems to be a feasible approach to obtain prolonged joint residence time.

Synthesis, spectral studies and anti-inflammatory activity of glycolamide esters of niflumic acid as potential prodrugs.

In order to reduce the gastric irritation caused by direct contact mechanism of the carboxylic acid group, a series of glycolamide esters of niflumic acid (CAS 4394-00-7) (1) have been prepared as bio-labile prodrugs by reacting appropriate 2-chloroacetamides with niflumic acid. The required 2-chloroacetamides were obtained by the condensation of chloroacetyl chloride and corresponding amine. Their structures were confirmed by UV, IR and 1H NMR spectra. Selected compounds were evaluated for anti-inflammatory activity in carrageenan induced paw oedema in rats at the doses of 45, 90 and 150 mg/kg b.w. Prodrugs showed comparable anti-inflammatory activity (67.1-79.4%) at 150 mg/kg b.w. with respect to niflumic acid (70.3%) at 45 mg/kg b.w., indicating moderate release of niflumic acid in vivo. The highest activity was observed with diethylamine (4) and pyrrolidine (9) derivatives.

Stability Studies of Some Glycolamide Ester Prodrugs of Niflumic Acid in Aqueous Buffers and Human Plasma by HPLC with UV Detection

Glycolamide esters (compounds 1-17) of 2-(3-trifluoromethyl-phenylamino)nicotinic acid (niflumic acid, CAS 4394-00-7) have been synthesized and evaluated as possible prodrugs. In-vitro hydrolysis studies were conducted at selected pH values (1.2, 3.5, 4.8, 7.4 and 7.8) and in human plasma at 37 +/- 0.5 degree C using HPLC with UV detection. The aqueous (pH 7.4 and 7.8) and enzymatic rates of hydrolysis were substantially affected by the nature of promoieties in this series. The compounds showed good chemical stability in the buffers of low pH values (1.2, 3.5 and 4.8) and appreciable hydrolysis under alkaline conditions and in human plasma. They exhibited long hydrolytic half-lives of 7-46 h in aqueous buffer solutions (pH 7.4 and 7.8) and 14-21 min in human plasma, respectively. It was observed that N,N-disubstituted and cyclic glycolamide derivatives showed 2 fold more hydrolysis in the alkaline pH than monosubstituted derivatives, whereas the piperidino and thiomorpholino derivatives did not undergo chemical hydrolysis. The compounds contain two possible sites for hydrolysis with an increased hydrolytic susceptibility at the terminal aliphatic carbonyl site in aqueous buffers and human plasma solutions. They were found to be cleaved at two hydrolytic carbonyls, namely the nicotinyl (2-5 % in enzymatic hydrolysis) and the aliphatic site (7-55 % and 70-85 % in buffer and plasma hydrolysis, respectively) as revealed by HPLC analysis. The glycolamide ester prodrugs of niflumic acid underwent chemical and enzymatic hydrolysis to release mainly the metabolite 2-(3-trifluoromethyl-phenylamino) nicotinic acid carboxymethyl ester (III) and not the parent drug 2-(3-trifluoromethyl-phenylamino)nicotinic acid. The structure of the metabolite was confirmed by liquid chromatography-mass spectroscopy (LCMS).

Facile plasma-catalysed degradation of penicillin alkyl esters but with no liberation of the parent penicillin.

The methyl ester and some glycolamide esters of benzylpenicillin and ampicillin were shown to be rapidly degraded by human plasma at 37 degrees C with no parent penicillin being produced. The plasma-catalysed degradation which was also observed in rat plasma proceeds most likely through hydrolytic cleavage of the beta-lactam bonds of the penicillin esters and is suggested to be due to the presence of an ester-specific beta-lactamase in plasma. The results show that the failure of simple alkyl esters of penicillins to function as prodrugs is not due to a high enzymatic stability of the esters, as widely believed, but rather to a pronounced susceptibility to undergo hydrolytic cleavage of their beta-lactam ring in-vivo. Since double ester prodrugs of penicillins, such as the pivaloyloxymethyl ester of ampicillin, are readily hydrolysed in plasma to yield the parent penicillin although at a rate lower than e.g. that of inactivation of a simple methyl ester, the plasma enzyme apparently attacking the beta-lactam bond of penicillin esters appears to have a high degree of specificity for the ester structure.

Prodrugs of scutellarin: Ethyl, benzyl and N, N-diethylglycolamide ester synthesis, physicochemical properties, intestinal metabolism and oral bioavailability in the rats

In an effort to enhance the oral bioavailability of scutellarin, ethyl, benzyl and N, N-diethylglycolamide ester of scutellarin were synthesized. The hydrolysis of the prodrugs follows first-order kinetics in aqueous solution, and produced a V-shaped pH profile. The N, N-diethylglycolamide ester is highly susceptible to enzymatic hydrolysis in human plasma ( t 1/2 ≈ 7 min) with a high stability in aqueous solution ( t 1/2 ≈ 16 day, pH 4.2). Compared with the solubility of scutellarin, the solubility of glycolamide ester was about ten times in pH 4.0 buffer, and about thirty five times in water. Its apparent partition coefficient increased significantly from −2.56 to 1.48. Glycolamide ester of scutellarin was chosen to investigate the intestinal metabolism and in vivo bioavailability. Degradation studies in the intestinal tract content and homogenates indicated intestinal metabolism before absorption was a crucial obstacle for the prodrug. N, N-Diethylglycolamide ester can be protected from the degradation in the intestinal lumen by an emulsion. A significant increase in the plasma AUC and C max of the prodrug emulsion was observed in rats, compared with that of the scutellarin–cyclodextrin complex ( P < 0.01). The emulsion of N, N-diethylglycolamide ester produces a 1.58-fold enhancement in apparent bioavailability and 1.4-fold increase in the absolute bioavailability compared to the scutallarin–cyclodextrin complex.

Evaluation of glycolamide esters of indomethacin as potential cyclooxygenase-2 (COX-2) inhibitors

A number of novel indomethacin glycolamide esters were synthesized and tested for their cyclooxygenase (COX-1 and COX-2) inhibition properties in vitro. Many of these compounds proved to be selective COX-2 inhibitors, and subtle structural changes in the substituents on the glycolamide ester moiety altered the inhibitory properties as well as potencies significantly. Their in vitro data were rationalized through molecular modeling studies. Few of them displayed anti-inflammatory activity in vivo. Compound 32, [1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1 H-indol-3-yl]acetic acid 2-morpholin-4-yl-2-oxo ethyl ester, was identified as a promising compound in this class and its good anti-inflammatory activity was demonstrated in the in vivo model.

Regioselective synthesis of peptidic derivatives and glycolamidic esters of Methotrexate

Convenient methods for regioselective syntheses of Methotrexate peptidic conjugates are described. Solid phase synthesis for derivatives of Methotrexate containing an amide bond has been applied and showed higher efficiency than liquid phase synthesis. Synthetic pathways for regioselective preparation of Glycolamidic ester derivatives of Methotrexate were also developed using 4-amino-4-deoxy-N 10-methylpteroic acid as starting material. These ester bonds were obtained either in solution or by using a combined liquid and solid phase synthesis.

Glycolamide Esters of 4‐Biphenylacetic Acid as Potential Prodrugs‐Synthetic and Spectral Studies.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Activity Profile of Glycolamide Ester Prodrugs of Ibuprofen

Glycolamide esters of ibuprofen (I), namely, unsubstituted (II), N, N dimethyl (III), and N, N diethyl (IV), were synthesized and studied for different physicochemical, pharmacological, and toxicological properties. They were comparable with I in respect of anti-inflammatory and analgesic activity but did not exhibit reduction in the ulcerogenicity on oral administration. However, all three exhibited significantly better topical activity in carrageenan-induced rat paw edema assay. In the same assay, they provided significant protection against inflammation when applied at a site remote to the inflammation site.

Glycolamide esters of 6-methoxy-2-naphthylacetic acid as potential prodrugs - physicochemical properties, chemical stability and enzymatic hydrolysis

Various glycolamide ester prodrugs of 6-MNA (I), an active metabolite of nabumetone (II), were synthesised to obtain NSAIDs with improved therapeutic index. To assess their suitability as prodrugs, these derivatives were evaluated for physicochemical properties, chemical stability and enzymatic hydrolysis in 80% human plasma. A number of these ester derivatives possessed physicochemical properties required for oral absorption (log P ≥ 2, solubility ≥ 10 μg/ ml). These esters were sufficiently stable in 0.05 M phosphate buffer of pH 7.4 at 37°C (half-lives 16–473 h). The disubstituted glycolamide esters XII-XXII were more stable than monosubstituted glycolamide esters IV-XI. Compound XII was also subjected to hydrolytic studies over the pH range 1.2–9.0 at 70°C and from the pH-rate profile, the pH of maximum stability was found to be 4.34 (4–5). At pH 4.5 compound XII showed a shelf life of 1.12 years at 20°C as determined from accelerated studies using the Arrhenius equation. The ester derivatives were quantitatively converted to 6-MNA very rapidly in human plasma at 37°C and pH 7.4 Comparison with chemical stability data shows that the intrinsic reactivity of esters has no effect on their enzymatic reactivity. The chemically most stable N,N-disubstituted glycolamide esters were better substrates for plasma enzymes (half-lives 7–83 s) compared to the monosubstituted glycolamide esters (half-lives 168–809 s). It is concluded that these derivatives possess many of the ideal properties of prodrugs and esterification of 6-MNA with substituted 2-hydroxyacetamides may be a potentially useful prodrug approach.

Chemically Modified Phosphocitrate and Entrapment in Microparticles for Sustained Inhibition of Biomineralization

Abstract Synthesis of glycolamide esters of phosphocitrate is described. Incorporation of salts or modified forms of phosphocitrate into albumin/polylactide based microspheres markedly improves efficiency in delivery. Strong inhibition of hydroxyapatite deposition into rat skin plaques was observed.

Continuous flow synthesis of peptides using a polyacrylamide gel resin (Expansin).

The continuous flow syntheses of endothelin 1, proendothelin 2, ATP binding site of the CDC2 kinase 3, and fragment 18-30 of an actin 4, have been performed by using a polyacrylamide gel resin Expansin (about 0.6 mmol NH2/g) with the glycolamidic ester handle as labile anchorage. In addition, we report here a method of air oxidation which reduces the formation of side-products related to the formation of intermolecular disulfide bridges.

Prodrugs as drug delivery systems. 107. Synthesis and chemical and enzymatic hydrolysis kinetics of various mono- and diester prodrugs of N-acetylcysteine

Abstract The systemic bioavailability of N -acetylcysteine (NAC) following oral administration is very low due to extensive first-pass metabolism by deacetylation, primarily in the gut. In an attempt to depress this metabolism and hence increase the systemic bioavailability various esters of NAC were synthesized and assessed as prodrug forms for the parent drug. The esters studied included alkyl esters, glycolamide esters and an acyloxymethyl ester formed at the carboxylic acid part of NAC as well as the S -benzoyl ester and various carboxylic acid esters thereof. An S -benzoyl carbamate ester was also studied. The pH-rate profiles for the hydrolysis of the derivatives were obtained at 37°C and interpreted in terms of hydrogen ion-, hydroxide ion- and water-catalyzed reactions. The hydrolysis of the oxy- and thioesters was enzymatically catalyzed by human and rat plasma as well as by rat liver and intestinal homogenate. The chemical and enzymic hydrolysis characteristics of the esters suggest that esterification of NAC at the carboxylic acid function or at the thiol group, or both, may be a potentially useful means to obtain prodrug forms of the drug for protecting it against intestinal deacetylation.

Furosemide prodrugs: synthesis, enzymatic hydrolysis and solubility of various furosemide esters

Various esters of furosemide were prepared and assessed as potential prodrugs with the aim of enhancing the peroral absorption characteristics of the parent drug. The esters studied included a neutral alkyl ester, alkyl esters containing an amino group, glycolamide esters and an O-acyloxymethyl ester. The esters showed widely different susceptibilities to undergo enzymatic hydrolysis in human plasma and rat liver homogenate, the propionyloxymethyl ester being the most reactive compound. The amino-containing esters were most soluble in water whereas all the esters were more lipophilic than furosemide as expressed by octanol-pH 7.4 buffer partition coefficients.

Glycolamidic ester handle used with polystyrene supports. Application to the synthesis of tp 5

Glycolamidic ester linkage of a peptide chain to a polystyrene resin can be easily cleaved under smooth alkaline conditions.

Carboxamidomethyl ester as useful handle in polystyrene-based peptide synthesis: Cleavage of peptide with mercaptide

Glycolamidic ester linkage of a peptide chain to a polystyrene resin can be cleaved with the lithium salt of mercaptoethanol, allowing utilization of this handle for Boc strategy of solid phase peptide synthesis.