Wang Resin Research Articles

Design, Synthesis and Biological Evaluation of Novel Peptide-Like Analogues as Selective COX-2 Inhibitors.

A new series of peptide-like derivatives containing different aromatic amino acids and possessing pharmacophores of COX-2 inhibitors as SO2Me or N3 attached to the para position of an end phenyl ring was synthesized for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. The synthetic reactions were based on the solid phase peptide synthesis method using Wang resin. One of the analogues, i.e., compound 2d, as the representative of these series was recognized as the most effective and the highest selective COX-2 inhibitor with IC50 value of 0.08 μM and COX-2 selectivity index of 351.2, among the other synthesized compounds. Molecular docking study was operated to determine possible binding models of compound 2d to COX-2 enzyme. The study showed that the p-azido-phenyl fragment of 2d occupied inside the secondary COX-2 binding site (Arg513, and His90). The structure-activity relationships acquired disclosed that compound 2d with 4-(azido phenyl) group as pharmacophore and histidine as amino acid gives the essential geometry to provide inhibition of the COX-2 enzyme with high selectivity. Compound 2d can be a good candidate for the development of new hits of COX-2 inhibitors.

Solid Phase Stepwise Synthesis of Polyethylene Glycols.

Polyethylene glycol (PEG) and derivatives with eight and twelve ethylene glycol units were synthesized by stepwise addition of tetraethylene glycol monomers on a polystyrene solid support. The monomer contains a tosyl group at one end and a dimethoxytrityl group at the other. The Wang resin, which contains the 4-benzyloxy benzyl alcohol function, was used as the support. The synthetic cycle consists of deprotonation, Williamson ether formation (coupling), and detritylation. Cleavage of PEGs from solid support was achieved with trifluoroacetic acid. The synthesis including monomer synthesis was entirely chromatography-free. PEG products including those with different functionalities at the two termini were obtained in high yields. The products were analyzed with ESI and MALDI-TOF MS and were found close to monodispersity.

Mitsunobu C-alkylation of β-alkoxycarbonyl 2-nitrobenzenesulfones and its use for the rapid synthesis of novel benzothiazine derivatives

Herein, we report the first examples of the Mitsunobu alkylation of β-alkoxycarbonyl 2-nitrobenzenesulfones. Wang resin was acylated with α-halocarboxylic acids followed by the reaction with 2-nitrothiophenols. After oxidation with m-chloroperbenzoic acid, the immobilized β-alkoxycarbonyl 2-nitrobenzensulfones were subjected to alkylation with various alcohols. The reaction outcome strongly depended on the selection of the alkylating species. After the reduction of the nitro group, acid-mediated cleavage and subsequent cyclization, the C2-(di)substituted benzothiazin-3(4H)-one 1,1-dioxides were obtained in high crude purities and good overall yields.

Synthetic Strategies for the Modification of Diclofenac

For many heterogeneous sensor applications as well as the synthesis of hapten antigens to produce antibodies, protein conjugates of the target substance are essential. A requirement is that the target substance already offers or is modified to contain a functionality that allows for coupling to a protein, that is, an amino acid residue. Ideally, to avoid shielding of the compound by the carrier protein, a sufficient distance to the protein surface should be provided. With its carboxyl function diclofenac (DCF) allows for direct binding to lysine residues after in situ synthesis of the NHS ester. One problem is that diclofenac as free acid tends to autocondensation, which results in low yields. Here we describe the ‘insertion’ of a C6 spacer via synthesis of the amide with 6-aminohexanoic acid. To carry out the reaction in solution, first the methyl ester of the amino acid had to be produced. Due to otherwise low yields and large cleaning efforts, solid-phase synthesis on Fmoc Ahx Wang resin is recommended. The crude product is mainly contaminated by cleavage products from the resin which were removed by chromatography. The structure of the highly pure hapten was completely determined by nuclear magnetic resonance (NMR) spectroscopy.

ChemInform Abstract: Sulfonic Acid—Functionalized Wang Resin (Wang‐OSO3H) as Polymeric Acidic Catalyst for the Ecofriendly Multicomponent Synthesis of Polyhydroquinolines via Hantzsch Condensation.

AbstractIn the title reaction, the Wang sulfonic acid acts as a very efficient and green promoter.

Sulfonic acid–functionalized Wang resin (Wang-OSO3H) as polymeric acidic catalyst for the ecofriendly multicomponent synthesis of polyhydroquinolines via Hantzsch condensation

ABSTRACTAn efficient and green approach has been developed for the synthesis of polyhydroquinoline derivatives via Hantzsch condensation reaction directly from corresponding substituted aromatic and aliphatic aldehydes, β-keto compounds, active methylene compounds, and ammonium chloride using recyclable polymer-supported sulfonic acid catalyst under aqueous conditions. Environmental acceptability, operational simplicity, low cost, excellent functional group compatibility, and high yields are the important features of this protocol.

Total synthesis, structural, and biological evaluation of stylissatin A and related analogs

The natural product cyclic peptide stylissatin A (1a) was reported to inhibit nitric oxide production in LPS-stimulated murine macrophage RAW 264.7 cells. In the current study, solid-phase total synthesis of stylissatin A was performed by using a safety-catch linker and yielded the peptide with a trans-Phe(7) -Pro(6) linkage, whereas the natural product is the cis rotamer at this position as evidenced by a marked difference in NMR chemical shifts. In order to preclude the possibility of 1b being an epimer of the natural product, we repeated the synthesis using d-allo-Ile in place of l-Ile and a different site for macrocyclization. The resulting product (d-allo-Ile(2) )-stylissatin A (1c) was also found to have the trans-Phe(7) -Pro(6) peptide conformations like rotamer 1b. Applying the second route to the synthesis of stylissatin A itself, we obtained stylissatin A natural rotamer 1a accompanied by rotamer 1b as the major product. Rotamers 1a, 1b, and the epimer 1c were separable by HPLC, and 1a was found to match the natural product in structure and biological activity. Six related analogs 2-7 of stylissatin A were synthesized on Wang resin and characterized by spectral analysis. The natural product (1a), the rotamer (1b), and (d-allo-Ile(2) )-stylissatin A (1c) exhibited significant inhibition of NO(.) . Further investigations were focused on 1b, which also inhibited proliferation of T-cells and inflammatory cytokine IL-2 production. The analogs 2-7 weakly inhibited NO(.) production, but strongly inhibited IL-2 cytokine production compared with synthetic peptide 1b. All analogs inhibited the proliferation of T-cells, with analog 7 having the strongest effect. In the analogs, the Pro(6) residue was replaced by Glu/Ala, and the SAR indicates that the nature of this residue plays a role in the biological function of these peptides. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Optimal peptide hydrazide ligation with C-terminus Asp, Asn, and Gln hydrazides

Peptide hydrazide ligation is a newly reported approach using C-terminus hydrazide as the precursor of thioester for ligation with N-terminus Cys-peptides. However, peptide hydrazides with C-terminus Asp, Asn, and Gln are difficult to generate because of cyclization side reaction happened during peptide cleavage from Wang resin. To prevent the cyclization, we chose the acid-sensitive CTC-resin as the support and utilized two-step cleavage strategy: (1) release the peptide hydrazide bearing side-chain protection from the support with 1% TFA; (2) remove the side-chain protection with 90% TFA to give the corresponding peptide hydrazides. Peptide ligation using these hydrazides with a Cys-peptide indicated the high efficiency in peptide elongation. The current study expands the scope of the peptide hydrazide ligation to all 20 natural amino acids at C-terminal.

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.

Removal of acid-labile protecting or anchoring groups in the presence of polyfluorinated alcohol: Application to solid-phase peptide synthesis

We describe herein a new method for cleaving from resin and removing acid-labile protecting groups in solid-phase peptide synthesis in the presence of a polyfluorinated alcohol (either trifluoroethanol, TFE, or hexafluoroisopropanol, HFIP). It was shown that 0.1 M HCl in hexafluoroisopropanol or trifluoroethanol removes the acid-labile protecting groups commonly used in Fmoc SPPS for the protection of amino acid side-chains, such as t-butyl ester and ether, Boc, trityl, and Pbf groups including the most acid-resistant p-hydroxymethylphenoxyacetyl group (HMPA), p-benzyloxy benzyl ester (Wang resin), Rink amide, and peptide amide linker (PAL). The addition of 5–10% of a hydrogen-bonding solvent was shown to considerably retard or even fully inhibit the reaction. However, nonhydrogen-bonding solvents, such as dichloromethane, do not slow down the reaction.

Development of solid-supported methodology for the preparation of peptidoglycan fragments containing (2S,6R)-diaminopimelic acid

Herein, we describe the development of an efficient solid-supported methodology for the stereoselective synthesis of two peptides containing (2S,6R)-diaminopimelic acid, (S)-Ala-γ-(R)-Glu-(2S,6R)-A2pm-(R)-Ala 1 and γ-(R)-Glu-(2S,6R)-A2pm 2. The platform consists of a Wang resin anchored by an amino acid chain including allylglycine. By olefin cross metathesis with vinylglycine, unsaturated protected (2S,6R)-A2pm was fixed on solid support. Peptides were achieved by cleavage of cross metathesis products from resin, followed by reduction of double bonds along removing of protecting groups. Furthermore, this efficient solid phase approach will lead to peptide and muropeptide libraries.

ChemInform Abstract: Sulfonic Acid Functionalized Wang Resin (Wang‐OSO3H) as Polymeric Acidic Catalyst for the Eco‐Friendly Synthesis of 2,3‐Dihydroquinazolin‐4(1H)‐ones.

Abstract An efficient and green approach has been developed for the synthesis of 2-substituted 2,3-dihydroquinazolin-4(1 H )-ones directly from corresponding substituted aromatic and aliphatic aldehyde and anthranilamide using recyclable polymer supported sulfonic acid catalyst under aqueous conditions. Environmental acceptability, operational simplicity, low cost, excellent functional group compatibility, and high yields are the important features of this protocol.

(1R,2R)-(+)-1,2-DPEN-modified Wang resin: An efficient catalyst for the asymmetric Michael addition of acetone to β-nitroolefins

Wang resin was modified by (1R,2R)-(+)-1,2-DPEN by means of a triazine ring. The catalyst was characterized by thermogravimetric (TG) analysis, elemental analysis, and Fourier transform infrared spectroscopy (FT-IR). Subsequently, this catalyst was employed for the asymmetric Michael addition of acetone to β-nitrostyrene. Under optimized conditions, 76.6% of β-nitrostyrene conversion and 82.8% enantioselectivity of Michael adduct were obtained. On the basis of the characterization of the catalyst by X-ray photoelectron spectroscopy (XPS), the mechanism of catalysis was proposed. In addition, the generality of the catalyst was evaluated with Michael additions of acetone to β-nitroolefins. Finally, the continuous reaction was realized in a fixed-bed reactor.

Preparation of a novel polymer monolith with high loading capacity by grafting block poly(PEGA–mPEGA) for high-efficiency solid phase synthesis

The polymer monolith for solid-phase synthesis with high efficiency was prepared through in situ copolymerization of chloromethylstyrene and ethylene glycol dimethacrylate (PCMS–EDMA). The obtained monolith was grafted by two kinds of poly(ethylene glycol) acrylate oligomer, poly(ethylene glycol) acrylate (PEGA) and poly(ethylene glycol) methyl ether acrylate (mPEGA). The monolith was grafted via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP) with the increased number of functional groups (–OH). About 0.61–0.81mmol/g hydroxyl group resulted from side groups in each grafting polymer chain. PmPEGA in the grafting block copolymer chains can increase the distance between the adjacent reactive sites of PEGA (–OH) in each polymer chain. Therefore, the grafted monoliths with the block copolymer of PEGA-co-mPEGA can give high yield (85%) and purity (93%) of the crude peptide (a difficult sequence-acyl carrier protein fragment 65–74) under the condition of high loading capacity (0.76mmol/g). These results were higher than those by the grafted monolith with only polymer of PEGA (72% and 81%, respectively) and commercial Wang resin (43% and 39%, respectively). The synthetic efficiency on the grafted monolith with block copolymer in the continuous flow technique was 5–6 folds higher than Wang resins in the manual operation conditions.

Sulfonic acid functionalized Wang resin (Wang-OSO3H) as polymeric acidic catalyst for the eco-friendly synthesis of 2,3-dihydroquinazolin-4(1H)-ones

An efficient and green approach has been developed for the synthesis of 2-substituted 2,3-dihydroquinazolin-4(1H)-ones directly from corresponding substituted aromatic and aliphatic aldehyde and anthranilamide using recyclable polymer supported sulfonic acid catalyst under aqueous conditions. Environmental acceptability, operational simplicity, low cost, excellent functional group compatibility, and high yields are the important features of this protocol.

Activation and deactivation of a robust immobilized Cp*Ir-transfer hydrogenation catalyst: a multielement in situ X-ray absorption spectroscopy study.

A highly robust immobilized [Cp*IrCl2]2 precatalyst on Wang resin for transfer hydrogenation, which can be recycled up to 30 times, was studied using a novel combination of X-ray absorption spectroscopy (XAS) at Ir L3-edge, Cl K-edge, and K K-edge. These culminate in in situ XAS experiments that link structural changes of the Ir complex with its catalytic activity and its deactivation. Mercury poisoning and "hot filtration" experiments ruled out leached Ir as the active catalyst. Spectroscopic evidence indicates the exchange of one chloride ligand with an alkoxide to generate the active precatalyst. The exchange of the second chloride ligand, however, leads to a potassium alkoxide-iridate species as the deactivated form of this immobilized catalyst. These findings could be widely applicable to the many homogeneous transfer hydrogenation catalysts with Cp*IrCl substructure.

Preparation of PEGA grafted poly(chloromethylstyrene-co-ethylene glycol dimethacrylate) monolith for high-efficiency solid phase peptide synthesis under continuous flow techniques

The polymer monolith for solid-phase synthesis was prepared through in situ copolymerization of chloromethylstyrene and ethylene glycol dimethacrylate (PCMS-EDMA), and the obtained monolith was grafted by poly (ethylene glycol) acrylate monomer via activators generated by electron transfer atom transfer radical polymerization (AGET ATRP). The novel monolith was highly crosslinked and showed no detectable swelling in both polar and nonpolar solvents (e.g. dichloromethane, dimethylformamide, tetrahydrofuran, acetonitrile, and methanol). The grafted monolith increased the number of functional groups in the range of 0.32–0.85 mmol/g, which resulted from side groups in each grafting polymer chain. Meanwhile, the grafted monolith showed good permeability and mechanical strength under the flow-through conditions. This monolith was derived into Wang resin and used in the synthesis of a difficult sequence-acyl carrier protein fragment 65–74 (ACP 65–74) in a new designed continuous flow equipment. The yield and purity of the crude peptide acquired from the grafted monolith reached 82% and 92%, respectively, which were higher than those by the ungrafted monolith (51% and 60%, respectively) or commercial Wang resin (51% and 61%, respectively). The synthetic efficiency on the grafted monolith in the continuous flow technique was 4–5 folds higher than on Wang resins in the manually operation conditions. Therefore, this monolithic resin showed potential effects in production scale-up.

Photoluminescent hybrid materials of lanthanide (Eu3+, Sm3+) polyoxometalates and polymer resin through ionic liquid linker

We achieve luminescent soft hybrid materials with lanthanide polyoxometalates and polymer resin (Merrifield resin (MR) or Wang resin (WR)) through ionic liquid compound (3-(2-(2-mercaptoacetoxy)ethyl)-1-methyl-1H-imidazol-3-ium bromide (SHIL)) as chemical linker, which are designated as LnW10-SHIL-MR(WR) (Ln = Eu, Sm). The photoluminescent properties of these hybrids are characterized, and it is found that they present excitation both in the ultraviolet and visible regions. Under the excitation at the visible region, the yellow-orange emission is obtained for the LnW10 unit. Subsequently, the white luminescence for the excitation at the visible region can be observed. This provides the useful data to prepare the white luminescent soft hybrids of polymer and lanthanide polyoxometalates through an ionic liquid linker.

Abstract 4588: Polylysine linker for successful manufacturing of hydrophobic peptides

Abstract Hydrophobic peptides are common to be used in cancer vaccinations. Hydrophobic peptides, continue to present challenges for large scale production in peptide industry. Experimental Procedures: Full sequence prepared by Solid phase Synthesis:The peptide was synthesized with Fmoc-Lys(Boc)-Wang resin by using standard Fmoc/tBu chemistry. Protecting groups used for amino acids are: tBu for Thr, Boc for Trp and Lys and Boc-Ser- OH was used as a hydrolysis-labile ester provider. Fmoc-Leu-OH was coupled on the side chain of Ser by DIC/DMAP (Amino acid/DIC/DMAP, 3/1.5/0.3 eq). The other amino acids were assembled by repetitive removal of the Fmoc protecting group by treating with 2% DBU/2% piperidine in DMF 30 minutes and coupling of protected amino acid by using DIC/HOBt/NMM (4:4:4 eq) in 180 minutes to overnight. Ninhydrin test was performed after each coupling to check the coupling efficiency. After the last coupling,resin was washed and dried, then treated with reagent K for cleavage and removal of the side chain protecting groups. Crude peptide was precipitated from cold ether and collected by filtration. Table.1 Summary of 4 synthesize results Syn. NoLinker StructurePurity of CrudeDKP deletion: Product Hydrolysis YieldOverall Yield1No Linker61.4%12.3%2(O)-Ser56.5%1:252.8%12.5%3(O)-Ac-Ser40.8%1:370.6%28.2%4HMBA78.1%<1:2451.0%61.2% Conclusion: American Peptide demonstrated the utility of a hydrophilic peptide ‘tail’ in purification of a hydrophobic peptide on both small (20-30 mmol) research scale and large (800 mmol) cGMP scales to provide the peptide in hundreds-of-grams quantities. The approach described allowed for both time-and cost-competitive manufacturing of this difficult peptide for clinical trials. Citation Format: Firuz Shakoori, Archana Gangakhedkar. Polylysine linker for successful manufacturing of hydrophobic peptides. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4588. doi:10.1158/1538-7445.AM2014-4588

Photoactive hybrid materials of lanthanide (Eu3+, Tb3+, Sm3+) beta-diketonates and polymer resin through ionic liquid bridge.

A special multifunctional ionic liquid compound (1-methyl-3-(2-(thiocarboxyoxy)-ethyl)-2H-imidazole-1,3-diium bromide (SHIL)) is used as the chemical bridge to link lanthanide beta-diketonates and polymer resin, which are designated as Ln(L)4-SHIL-WR/MR (Ln = Eu, Tb, Sm; L = thenoyltrifluoroacetonate (TTA), acetylacetonate (AA), dibenzoylmethane (DBM); WR = Wang resin, MR = Merrifield resin). Among SHIL and polymer resin are assembled to form covalently bonded system through condensation reaction. Then tetrakis lanthanide beta-diketonates are linked to SHIL through ion-exchange reaction. Physical characterization and especially the photoluminescent performance of the multicomponent hybrids are studied. The hybrid materials possess good stability and excellent luminescent property. The results provide useful path to obtain luminescent hybrids for further practical application.