Crude Purity Research Articles

Efficient automated solid-phase synthesis of recognition-encoded melamine oligomers.

Recognition-encoded melamine oligomers (REMO) are synthetic polymers with an alternating 1,3,5-triazine-piperazine backbone and side chains equipped with either a phenol or phosphine oxide recognition unit. Here, we describe an automated method for highly efficient solid-phase synthesis (SPS) of REMO of any specified length and sequence. These SPS protocols are amongst the most robust reported to date, as demonstrated by the synthesis of a mixed-sequence 42-mer, which was obtained in excellent crude purity on a 100 mg scale. Starting from loaded Wang resin and dichlorotriazine monomer building blocks, the SPS methods were automated and optimised on a commercial peptide synthesiser. Major side products were identified using LCMS, and the undesired side reactions were suppressed by the choice of resin, solvent and coupling conditions. REMO have been shown to form high-fidelity length- and sequence-selective H-bonded duplexes, analogous to nucleic acids, and automated synthesis will facilitate exploration of related functional properties, such as molecular replication and programmable self-assembly.

Pemanfaatan Fly Ash sebagai Adsorben dalam Pemurnian Crude Glycerol dari Hasil Produk Samping Biodiesel

The increase of biodiesel production capacity is followed by an increase in crude glycerol production as a by-product. Crude glycerol still has a low purity and a lot of impurities so it requires special treatment so that it can be utilized and valuable. One of the ways to increase the purity of crude glycerol is in the adsorption process. This study aims to determine the best conditions for the adsorption process and the characteristics of the glycerol produced after the adsorption process. The initial condition of crude glycerol purity is low, namely 67.8%, so purification is needed. One way of purifying crude glycerol is by physically separating it using fly ash as an adsorbent. The experiment was carried out with the adsorption process using fly ash with the adsorbent mass variable 30,35,40,45, and 50 grams and the adsorption time variable was 50,60, and 70 minutes. The purified products are analyzed quantitatively and qualitatively, including glycerol content, density, viscosity, moisture content, ash, and MONG. The best conditions for the adsorption process using fly ash were obtained at a mass of 50 grams with a time of 50 minutes with the results that the glycerol content was 97.5%, water content 0.03%, ash content 0.0432%, MONG content 2.426%, density 1.253 gr / ml , viscosity 233.56 cP. Based on these results, purified glycerol was obtained that met the quality standards of SNI 06-1564-1995.

C-phycocyanin production with high antioxidant activity of a new thermotolerant freshwater Desertifilum tharense UAM-C/S02 strain

A native cyanobacterial strain, Desertifilum tharense UAM-C/S02, was studied as a possible C-phycocyanin (C-PC) producer. Photosynthetic activity (PA) assays through oxygen production determined the proper temperature and range of irradiances to be tested in a stirred tank photobioreactor. The highest C-PC productivity (97 mg L−1 d−1), with a yield of 86.46 mgC-PC gB−1 was obtained at 730 µmol photons m−2 s−1 with a biomass productivity of 608 mg L−1 d−1 and the CO2 fixation rate was 1,194 mg L−1 d−1. The 1.81 crude extract purity value is the highest reported for this genus, which was improved to biomarker-grade purity after a two-step purification strategy comprising precipitation with ammonium sulfate, followed by dialysis. The purified C-PC was almost entirely radical-free using 1 mg mL−1, which validates its potential use in therapeutic formulations.

Evaluation of unexpected protecting group removal in solid-phase peptide synthesis: Quantified using continuous flow methods.

As peptides gained interest as new drugs in the past years, their synthetic routes had been the subject of review and improvement. Fmoc/tBu-based solid-phase peptide synthesis (SPPS) is the most convenient technique, and the implementation in continuous flow has allowed for single-pass coupling and deprotection reactions. The focus of this research is to evaluate the relationship between undesired solvent-promoted reactions and final crude purity, by studying volume changes of a variable bed flow reactor through the synthesis. Based on the temperature, typical solvents for SPPS such as dimethylformamide (DMF) or N-methyl-2-pyrrolidone (NMP) can cause unwanted Fmoc removal during wash steps. It was found that for every millilitre of DMF used at 80°C, up to 1μmol of Fmoc-protected peptide is deprotected, leading to additional impurities. This effect can, however, be minimised by adding additives such as HOBt, which reduces such unwanted deprotection to just 0.1μmol/ml.

A novel synthetic method of peptide nucleic acid (PNA) oligomers using Boc/Cbz‐protected PNA trimer blocks in the solution phase

AbstractIn order to use peptide nucleic acid (PNA) oligomers for therapeutic purposes, a high purity level is essential and, in particular, large‐scale production should be easy. However, in the traditional solid‐phase synthesis method, the generation of n − 1 or n − 2 deleted oligomers cannot be completely excluded, and purification of crude oligomers is difficult because the target and impurities overlap. Also, for these reasons, scale‐up is also limited. Here, we report the efficient synthesis of PNA oligomers in the solid phase using fully protected PNA trimers instead of monomers. Fully protected PNA trimer blocks were successfully synthesized via two different routes in the solution phase. When PNA oligomers were synthesized in the solid phase using trimer blocks as monomers, a higher purity level of PNA could be synthesized compared to when oligomers were synthesized using monomers. When using this method, n − 1 or n − 2 truncated products cannot be systematically produced. Furthermore, the trimer blocks coupling method is successful even for sequences containing purine‐rich and/or gamma PNAs, which are difficult to synthesize via the conventional solid‐phase peptide synthesis approach. Finally, two hexameric and one dodecameric PNA oligomers were completely synthesized in the solution phase, with the former showing more than 90% crude purity and the latter showing 70%. We propose that this method may be able to solve several problems related to solid‐phase synthesis at once.

Amino-Li-Resin-A Fiber Polyacrylamide Resin for Solid-Phase Peptide Synthesis.

Amino-Li-resin is a new and unique polyacrylamide resin presented in the form of fibers and is found to be well suited for solid-phase peptide chemistry. Although amino-Li-resin swells much better in polar solvents, it is also compatible with some non-polar solvents. It comes with a high loading of functional amino groups, thus maximizing its productivity in terms of the amount of peptide per gram of resin. In addition to its mechanical stability, this resin shows excellent stability in basic and acidic reagents; thus, allowing its broad applicability for the synthesis of a wide range of biomolecules. Finally, the appropriateness of amino-Li-resin for solid-phase peptide synthesis (SPPS) has been demonstrated for the synthesis of several model peptides, including difficult sequences and those containing hindered amino acids, all of which afforded excellent crude purity, as shown by high-performance liquid chromatography (HPLC) analysis.

Ultrasonication Improves Solid Phase Synthesis of Peptides Specific for Fibroblast Growth Factor Receptor and for the Protein-Protein Interface RANK-TRAF6.

Considering our interest in the use of peptides as potential target-specific drugs or as delivery vectors of metallodrugs for various biomedical applications, it is crucial to explore improved synthetic methodologies to accomplish the highest peptide crude purity in the shortest time possible. Therefore, we compared “classical” fluorenylmethoxycarbonyl (Fmoc)-solid phase peptide synthesis (SPPS) with ultrasound(US)-assisted SPPS based on the preparation of three peptides, namely the fibroblast growth factor receptor 3(FGFR3)-specific peptide Pep1 (VSPPLTLGQLLS-NH2) and the novel peptides Pep2 (RQMATADEA-NH2) and Pep3 (AAVALLPAVLLALLAPRQMATADEA-NH2), which are being developed aimed at interfering with the intracellular protein-protein interaction(PPI) RANK-TRAF6. Our results demonstrated that US-assisted SPPS led to a 14-fold (Pep1) and 4-fold time reduction (Pep2) in peptide assembly compared to the “classical” method. Interestingly, US-assisted SPPS yielded Pep1 in higher purity (82%) than the “classical” SPPS (73%). The significant time reduction combined with high crude peptide purity attained prompted use to apply US-assisted SPPS to the large peptide Pep3, which displays a high number of hydrophobic amino acids and homooligo-sequences. Remarkably, the synthesis of this 25-mer peptide was attained during a “working day” (347 min) in moderate purity (approx. 49%). In conclusion, we have reinforced the importance of using US-SPPS towards facilitating the production of peptides in shorter time with increased efficacy in moderate to high crude purity. This is of special importance for long peptides such as the case of Pep3.

Comparison of three methods for thermostable C-phycocyanin separation and purification

The efficient separation and purification methods are the major obstacles in the production and further use of bioproducts. One such valuable bioproduct is the thermostable C-phycocyanin (C-PC). There is a great commercial need to develop C-PC production with an appropriate degree of purity. However, the selected methods and their sequences are also depended on the quality of crude extract obtained from biomass. In this paper three down-stream processing methods, such as foam fractionation (FF), which according to our knowledge has not been used for separation of C-PC, aqueous two-phase extraction (ATPE) and conventional ultrafiltration were investigated for purification of thermostable C-PC from two crude extracts with lower and higher protein concentration and purity obtained from biomass of Synechococcus sp. PCC6715. The FF process resulted in a recovery yield of 49% and a purification factor of 1.472 without the addition of surfactants or pH adjustment. The most effective ATPSystem consists of polyethylene glycol 6000 and phosphate salt with a recovery yield of 97%, partitioning coefficient of about 28 and purification factor of 1.466. Ultrafiltration gave a recovery yield of 92% and purification factor of 1.123. Two possible ways of C-PC purification depending on the crude extract purity and concentration was proposed.

Tag‐Assisted Liquid‐Phase Synthesis of Peptoids

Optimized reaction conditions for the tag-assisted liquid-phase synthesis of peptoids are reported. A peptoid heptamer was obtained in >90% crude purity at an elevated temperature and in chloroform. This liquid-phase peptoid synthesis can be an alternative method for preparing large quantities of peptoid oligomers.

The quality of crude glycerine influences the fermentation and nutritive value of Piatã grass silage

ABSTRACT We aimed to evaluate the effects of crude glycerine purity and levels of glycerol on the fermentative profile, microorganisms counting, and nutritional value of Piata grass silage. The experiment was carried out in a 3×3+1 completely randomized factorial design using three different types of crude glycerine [low purity (40% of glycerol), medium purity (60% glycerol), and high purity (80% glycerol)], three doses of glycerol (20, 40, and 60 g/kg DM), and a control (no crude glycerine added) as an [...]

Biphasic Aqueous Reaction Conditions for Process-Friendly Palladium-Catalyzed C–N Cross-Coupling of Aryl Amines

We herein describe a method for palladium-catalyzed C–N cross-coupling of aryl amines and aryl halides in a biphasic reaction medium composed of 2-methyltetrahydrofuran (MeTHF) and water. By effective solubilization of the inorganic base used, common challenges associated with the scalability of Buchwald–Hartwig aminations using inorganic bases were circumvented. The mildly basic nature of the reaction conditions was highlighted by the facile coupling of a base-sensitive substrate, which could be converted to the corresponding product with a high level of crude purity. The method is operationally simple and displays an improved safety and sustainability profile compared with many alternative strategies for large-scale Buchwald–Hartwig amination. Relying on a commonly available dialkylbiarylphosphine ligand, this approach was applied to three clinically relevant C–N cross-coupling reactions on the hecto- to kilogram scale.

Physicochemical Properties of Kakamut Gum (<i>Acacia polyacantha</i>) and Hashab Gum (<i>Acacia senegal</i>): A Comparative Analysis

The physicochemical properties of the natural Gum are very important in determining their commercial value and their use. Herein, the present study aims to identify differences in physicochemical properties of Kakamut Gum (Acacia polyacntha) and Hashab Gum (Acacia Senegal). Samples of Gums were collected as follows: Kakamut Gum from Um fakarin forest and Hashab Gum from Eldemokeya forest, North Kordofan State 2008 – 2009. The two samples were subjected to laboratory analyzed in Warm Seas Agro Business, Elobeid Agricultural Research Station, and Sudanese Standards and Metrology Organization. The study revealed that there were significant differences (p < 0.01) in moisture (dry matter) and optical rotation. Also, significant differences (p < 0.05) were found in the percentage of ash content and viscosity. However, there were no significant differences found in the percentage of the crude fiber, nitrogen (protein), pH, and purity between the two samples. The results obtained demonstrate clearly the physical and chemical characteristics of the two Gums samples and also, throw lights on their nutritional purposes. As well as the study of the physicochemical properties of Kakamut Gum and compare it with Hashab Gum, proved the potential contribution of the Kakamut tree (Acacia Polyacantha) in the Gum production and not depend solely on the Gum produced from the Hashab tree (Acacia Senegal).

An Alkyne Rod to Constrain a Peptide Backbone in an Extended Conformation

An N,N′‐bound rod‐shaped diyne bridge was introduced into a peptide to constrain the peptide backbone in an extended conformation. Linear precursors were achieved via solid‐phase synthesis using simple commercially available building blocks. Subsequently, 13‐ to 15‐membered peptide macrocycles were obtained in excellent crude purity via in solution copper‐catalyzed cyclization. Density functional theory calculations of the lowest energy conformers suggested that the strain inside the macrocycle caused only slight deformation of the binding angles of the butadiyne moiety.

Synthesis of 2-Alkylsulfonyl-imidazoles with Three Diversity Positions from Immobilized α-Acylamino Ketones.

The synthesis of novel imidazole derivatives via immobilized α-acylamino ketones is reported in this article. The key intermediates were prepared from the Wang-piperazine resin-supported Fmoc-amino acids. After their sulfonylation with 4-nitrobenzenesulfonyl chloride (4-Nos-Cl), followed by alkylation with α-bromoketones and cleavage of Nos group, the resulting α-acylamino ketones were reacted with Fmoc-isothiocyanate. The corresponding Fmoc-thioureas were subjected to the Fmoc-cleavage and spontaneous ring-closure to imidazole scaffold. The resulting imidazole-thiones were alkylated with alkyl halides and oxidized using meta-chloroperbenzoic acid ( mCPBA). Trifluoroacetic acid (TFA)-mediated cleavage yielded the corresponding trisubstituted 2-alkylsulfonyl imidazoles in good crude purity and acceptable overall yields. In the case of sulfides, prepared from alkyl bromides, the unexpected products brominated at the C4 position of the imidazole were obtained.

Traceless Solid-Phase Synthesis of [6,7,8 + 5,6,7]-Fused Molecular Frameworks.

We report two synthetic strategies for traceless solid-phase synthesis of molecular scaffolds comprising 6- to 8-membered rings fused with 5- to 7-membered rings. Traceless synthesis facilitated preparation of target molecules without any trace of polymer-supported linkers. The cyclization proceeded via acid-mediated tandem N-acylium ion formation followed by the nucleophilic addition of O- and C-nucleophiles. The presented synthetic strategy enabled, through the use of simple building blocks without any conformational preferences, the evaluation of the predisposition of different combinations of ring sizes to form fused ring molecular scaffolds. Compounds with any combination of [6,7 + 5,6,7] ring sizes were accessible with excellent crude purity. The 8-membered cyclic iminium was successfully fused only with the 5-membered cycle and larger fused ring systems were not formed, probably due to their instability.

In-loop flow [11 C]CO2 fixation and radiosynthesis of N,N'-[11 C]dibenzylurea.

Cyclotron‐produced carbon‐11 is a highly valuable radionuclide for the production of positron emission tomography (PET) radiotracers. It is typically produced as relatively unreactive carbon‐11 carbon dioxide ([11C]CO2), which is most commonly converted into a more reactive precursor for synthesis of PET radiotracers.The development of [11C]CO2 fixation methods has more recently enabled the direct radiolabelling of a diverse array of structures directly from [11C]CO2, and the advantages afforded by the use of a loop‐based system used in 11C‐methylation and 11C‐carboxylation reactions inspired us to apply the [11C]CO2 fixation “in‐loop.” In this work, we developed and investigated a new ethylene tetrafluoroethylene (ETFE) loop‐based [11C]CO2 fixation method, enabling the fast and efficient, direct‐from‐cyclotron, in‐loop trapping of [11C]CO2 using mixed DBU/amine solutions. An optimised protocol was integrated into a proof‐of‐concept in‐loop flow radiosynthesis of N,N′‐[11C]dibenzylurea. This reaction exhibited an average 78% trapping efficiency and a crude radiochemical purity of 83% (determined by radio‐HPLC), giving an overall nonisolated radiochemical yield of 72% (decay‐corrected) within just 3 minutes from end of bombardment.This proof‐of‐concept reaction has demonstrated that efficient [11C]CO2 fixation can be achieved in a low‐volume (150 μL) ETFE loop and that this can be easily integrated into a rapid in‐loop flow radiosynthesis of carbon‐11–labelled products.This new in‐loop methodology will allow fast radiolabelling reactions to be performed using cheap/disposable ETFE tubing setup (ideal for good manufacturing practice production) thereby contributing to the widespread usage of [11C]CO2 trapping/fixation reactions for the production of PET radiotracers.

4‐(4,6‐Dimethoxy‐1,3,5‐triazin‐2‐yl)‐4‐methylmorpholinium Toluene‐4‐sulfonate (DMT/NMM/TsO−) Universal Coupling Reagent for Synthesis in Solution

4‐(4,6‐Dimethoxy‐1,3,5‐triazin‐2‐yl)‐4‐methylmorpholinium toluene‐4‐sulfonate (DMT/NMM/TsO−), a representative member of the inexpensive and environmentally‐friendly N‐triazinylammonium family of sulfonates, has been found to be a very effective coupling reagent for the synthesis of amides, esters and peptides in solution. This study confirms the usefulness of DMT/NMM/TsO− for peptide synthesis in solution, starting from Z‐, Fmoc‐, and Boc‐protected substrates as well as unnatural building blocks. Peptide synthesis with DMT/NMM/TsO− produced high yields, with high crude product purity and low risk of racemization. In all cases, stoichiometric amounts of reagents were used and the standard synthetic procedure, without the need for time‐consuming optimization stages or expensive chromatographic purification. DMT/NMM/TsO− was also found to be very useful for the synthesis of oligopeptides using a fragment coupling strategy.

Microwave heating in peptide side chain modification via cysteine alkylation.

Microwave irradiation has been successfully applied to a selective synthetic procedure for introducing molecular substituents on peptides, providing a noticeable reduction of the reaction time and also an increased crude peptide purity for some compounds.

Solid-Phase Synthesis of 2,3-Dihydrobenzo[f][1,2,5]thiadiazepin-4(5H)-one 1,1-Dioxides with Three Diversity Positions.

Synthesis of 2,3-dihydrobenzo[f][1,2,5]thiadiazepin-4(5H)-one 1,1-dioxides from polymer-supported α-amino acids is described herein. Different α-amino acids immobilized on Wang resin were sulfonylated with various 2-nitrobenzenesulfonyl chlorides. The resulting 2-nitrobenzenesulfonamides were alkylated with alcohols according to the Fukuyama-Mitsunobu procedure. After reduction of the nitro group and cleavage from the polymer support, the final intermediates were reacted with thionyl chloride, and target compounds of good crude purity and acceptable overall yields were obtained. The chiral HPLC studies revealed the impact of the cyclization step on the resulting stereochemistry. The developed strategy allows for simple production of desired compounds with the application of parallel/combinatorial solid-phase synthesis using commercially available building blocks.

First total synthesis of WLIP: on the importance of correct protecting group choice.

Cyclic lipodepsipeptides (CLPs) are a group of metabolites produced by Pseudomonas bacteria, involved in various biological functions and displaying a wide range of properties, including antibacterial and antifungal activities. The white line-inducing principle (WLIP) is a member of the viscosin group featuring a Glu2 amino acid. Recently, a total synthesis of pseudodesmin A - the Gln2 counterpart of WLIP - was described, and we here expand this route to Glu2 containing CLPs. We report the first total synthesis of WLIP and at the same time establish that the Gln2 to Glu2 substitution has an adverse impact on the crude purity and overall yield. A comparative study of different CLP analogues reveals the importance of the nature of the Glx2 protecting group in determining these outcomes. Replacement of the conventional tBu protecting group by the larger benzyl group for the Glu residue in our synthesis strategy indeed resulted in an improved conversion. Next to achieving the first WLIP total synthesis, we thus show the importance of a careful choice of protecting groups for the success of this type of solid-phase synthesis approaches towards CLPs.