Non-chromatographic Purification Research Articles

Self-assembling chimeric polypeptides as drug-carrying nanoparticles for anti-cancer chemotherapy

Abstract. Chemotherapy is often limited by unfavorable pharmacokinetics and pharmacodynamics that result in dose-limiting cytotoxicity. Therefore, self-assembling nanoparticles have been of particular interest to address these limitations by altering the physicochemical properties of payloads. Amphiphilic chimeric polypeptides (CPs) capable of versatile payload conjugation and spontaneous self-assembly into monodisperse micelles were designed, recombinantly synthesized, and characterized in this study. Doxorubicin (Dox) was also conjugated onto CPs to determine the effectiveness of pH-mediated release and the effects of payload conjugation on CP morphology. The designed CP consisted of a hydrophilic elastin-like polypeptide that enabled non-chromatographic polypeptide purification, an aspartic acid linker, a short Cys-rich segment for drug conjugation, and a hydrophobic domain that promoted the spontaneous formation of CP nanoparticles. Additionally, bio-orthogonal conjugation of chemotherapeutics onto CPs through short acid-labile chemical linkers enabled controlled pH-mediated release of conjugated chemotherapeutics and enhanced self-assembly. Results indicated that CP and Dox-CP nanoparticles had critical aggregation concentrations of 3.24 and 0.58 M and hydrodynamic radii of 57.09 and 72.86 nm, respectively. Dox-CP also released 76.8% of conjugated chemotherapeutics after 24 hours in late endosome pH and was effective against triple-negative breast cancer cells. These favorable characteristics and the independent self-assembly of the designed CP will enable targeted chemotherapeutic delivery regardless of payload hydrophobicity.

Environmentally Benign and Expeditious Access to 4‐Aryl Methylene‐isoxazole‐5(4H)‐Ones Using Magnetically Separable Nanoparticles

AbstractAn environmentally benign and expeditious protocol was developed for the one‐pot multicomponent synthesis of 4‐aryl‐3‐methylisoxazol‐5(4H)‐ones by the condensation of aldehyde, hydroxyl amine hydrochloride, and ethyl acetoacetate in 50% aq. ethanol at 50 °C. The reaction was catalyzed by magnetically separable carbon microspheres co‐decorated with nanosized iron sulfide and magnetite nanoparticles in 10 wt% amount. The FeS1‐x‐Fe3O4/C nanocatalyst was prepared from iron(III) sulfate loaded iminodiacetate group functionalized styrene‐divinylbenzene based ion exchanger by pyrolysis reaction performed at 600 °C for 4 h. The use of magnetically separable heterogeneous catalyst, aqueous ethanol, short reaction time (30 min), and nonchromatographic purification methods are the striking features of the developed protocol. The isolated yield of the condensation products varied between 81% and 96%. Furthermore, the protocol exhibits high functional group tolerance and includes the use of noncorrosive, nonhazardous reaction conditions affording the product in excellent yields and short reaction time.

SO2F2 mediated click chemistry enables modular disulfide formation in diverse reaction media

The dynamic disulfide linkage plays a vital role in various biological processes as well as drugs and biomaterials. The conversion of thiols to their corresponding disulfides is a hallmark of sulfur chemistry, but notoriously difficult to control. Achieving optimal reactivity and selectivity continues to pose significant challenges. Here, we describe a click chemistry for disulfide formation from thiols in both batch and flow-mode using SO2F2, which display exceptional selectivity toward disulfide formation through an effective nucleophilic substitution cascade. This reaction’s unique characteristics satisfy the stringent click-criteria with its high thermodynamic driving force, straightforward conditions, wide scope, quantitative yields, exceptional chemoselectivity, and non-chromatographic purification process. The modular synthesis of symmetrical, unsymmetrical, cyclic and polydisulfides is demonstrated, along with the formation of disulfide cross-linked hydrogels.

RAPID AND AN EFFICIENT ONE-POT THREE-COMPONENT SYNTHESIS OF ISOXAZOLES PROMOTED BY CAS

A straightforward, practical, and economical process for producing isoxazole derivatives is described. It makes use of ethylacetoacetate, hydroxylamine hydrochloride, and substituted aromatic aldehydes with promoted camphor sulfonic acid as a catalyst in a solvent. No toxic organic solvents are used in the current procedure. Shortest reaction time, high product yields, easy work-up process, and non-chromatographic product purification are only a few of this catalysts encouraging reaction response characteristics. The derivatives of desired compounds were analyzed advanced spectroscopic data by 1H NMR, 13CNMR and mass spectrometry was used to verify the products structures. Products were chosen, and their antibacterial activity was examined.

Enzyme purification and sustained enzyme activity for pharmaceutical biocatalysis by fusion with phase-separating intrinsically disordered protein.

In recent decades, biocatalysis has emerged as an important alternative to chemical catalysis in pharmaceutical manufacturing. Biocatalysis is attractive because enzymatic cascades can synthesize complex molecules with incredible selectivity, yield, and in an environmentally benign manner. Enzymes for pharmaceutical biocatalysis are typically used in their unpurified state, since it is time-consuming and cost-prohibitive to purify enzymes using conventional chromatographic processes at scale. However, impurities present in crude enzyme preparations can consume substrate, generate unwanted byproducts, as well as make the isolation of desired products more cumbersome. Hence, a facile, nonchromatographic purification method would greatly benefit pharmaceutical biocatalysis. To address this issue, here we have captured enzymes into membraneless compartments by fusing enzymes with an intrinsically disordered protein region, the RGG domain from LAF-1. The RGG domain can undergo liquid-liquid phase separation, forming liquid condensates triggered by changes in temperature or salt concentration. By centrifuging these liquid condensates, we have successfully purified enzyme-RGG fusions, resulting in significantly enhanced purity compared to cell lysate. Furthermore, we performed enzymatic reactions utilizing purified fusion proteins to assay enzyme activity. Results from the enzyme assays indicate that enzyme-RGG fusions purified by the centrifugation method retain enzymatic activity, with greatly reduced background activity compared to crude enzyme preparations. Our work focused on three different enzymes-a kinase, a phosphorylase, and an ATP-dependent ligase. The kinase and phosphorylase are components of the biocatalytic cascade for manufacturing molnupiravir, and we demonstrated facile co-purification of these two enzymes by co-phase separation. To conclude, enzyme capture by RGG tagging promises to overcome difficulties in bioseparations and biocatalysis for pharmaceutical synthesis.

Synthesis, Computational and Antimicrobial Study of 2-(2-Hydrazinyl)thiazole Derivatives

In the present investigation, we report a combined computational and experimental study of eight thiazole derivatives (4a-4h) obtained from 3,4-dihydronaphthalen-1(2H)-one. A green chemistry protocol comprising PEG-400 and sulfamic acid was employed for the synthesis of eight diverse thiazole derivatives from 3,4-dihydronaphthalen-1(2H)-one, thiosemicarbazide and various phenacyl bromides. The synthetic strategy provides benefits like short reaction time, high yield, and non-chromatographic purification. The compounds were structurally confirmed on the basis of IR, 1HNMR and 13C NMR. The obtained thiazole derivatives were studied using the density functional theory (DFT) method employing B3LYP/6-311G(d,p) level of theory for optimization and Time-Dependent DFT (TD-DFT) approach for examining electronic energies and UV-Vis characteristics. Various computational parameters like bond length, bond angles, HOMO, LUMO, MESP, Mulliken charges, and global descriptors are obtained and discussed. The UV-Vis study the in gas phase and DMSO solvent was investigated to obtain various insights such as absorption energies oscillator strength, configurations and transitions of examined thiazole derivatives. The effect of polar solvent has augmented the absorption wavelength of all studied thiazole derivatives. The experimental and simulated UV-Vis data correlate with each other prompting the effectiveness of the computed method. The scaled and experimental wavenumbers provided the appropriate assignment of various vibrational signals. The antibacterial study was performed against E. coli, P. aeruginosa, and S. aureus which demonstrated the strong antibacterial potential against S. aureus. The antifungal study against C. albicans revealed that these compounds are poor antifungal agents. The DPPH and OH radical assays were used to establish the % radical scavenger effects and results showed that these derivatives are good antioxidant agents. The % hemolytic activity of the tested compounds showed that all compounds fall within the acceptable toxicity limit. Importantly in slico ADME and toxicity prediction studies of these compounds highlighted good ADME profile with no hepatotoxicity, immunotoxicity and cytotoxicity.

Use of the selected metal-dependent enzymes for exploring applicability of human annexin A1 as a purification tag

Several fusion tags have been developed for non-chromatographic fusion protein purification. Previously, we identified that human annexin A1 as a novel N-terminal purification tag was used for purifying the fusion proteins produced in Escherichia coli through precipitation in 10mM Ca2+ buffer, and redissolution of the precipitate in 15mM EDTA buffer. In this work, we selected four metal-dependent enzymes including E.coli 5-aminolevulinate dehydratase, yeast 3-hydroxyanthranilate 3,4-dioxygenase, maize serine racemase and copper amine oxidase for investigating the annexin A1 tag applicability. Fusion of the His6-tag or the enzyme changed the behavior of precipitation-redissolution. The relatively high recovery yields of three tagged enzymes with the improved purities were obtained through two rounds of purification, whereas low recovery yield of the annexin A1 tagged maize amine oxidase was prepared. The added EDTA displayed different abilities to redissolve the fusion proteins precipitates in two precipitation-redissolution cycles. It inactivated three enzymes and obviously inhibited the activity of the fused maize serine racemase. Based on current findings, we believe that four enzymes could be applied for evaluating applicability of the proteins or peptides as affinity tags for chromatographic purification in a calcium dependent manner.

SnO2 nanoparticles: A recyclable and heterogeneous catalyst for Pechmann condensation of coumarins and Knoevenagel condensation–Michael addition of biscoumarins

Recyclable SnO2 nanoparticles catalyze the Pechmann condensation between phenolic alcohols and β-ketoesters at room temperature in ethanol leading to coumarins. Also, in another study the synthesis of biscoumarins catalyzed by SnO2 nanoparticles in the reaction between 4-hydroxycoumarin and aldehydes under same condition reactions. The corresponding coumarins and biscoumarins were produced efficiently with facility and excellent yields (93–98%). These approaches display the advantages of benign reaction conditions, non-chromatographic purification procedure, appropriate functional group tolerance and valuable process.

Cation affinity purification of histidine-tagged proteins.

Protein purification is a basic technology in both biological research and industrial production, and efficient, convenient, economical, and environmentally friendly purification methods have always been pursued. In this study, it was found that alkaline earth metal cations (Mg2+, Ca2+) and alkali metal cations (Li+, Na+, K+) and even nonmetal cations (e.g., NH4+, imidazole, guanidine, arginine, lysine) can precipitate multi-histidine-tagged proteins (at least two tags in a whole protein) at low salts concentrations that are 1-3 orders of magnitude lower than salting-out, and precipitated proteins could be dissolved at moderate concentration of corresponding cation. Based on this finding, a novel cation affinity purification method was developed, which requires only three centrifugal separations to obtain highly purified protein with purification fold similar to that of immobilized metal affinity chromatography. The study also provides a possible explanation for unexpected protein precipitation and reminds researchers to consider the influence of cations on the experimental results. The interaction between histidine-tagged proteins and cations may also have broad application prospects. KEY POINTS: • Histidine-tagged proteins can be precipitated by low-concentrations common cations • A novel nonchromatographic protein purification method was developed • Purified protein can be obtained in pellet form by only three centrifugations.

Fe Doped Ga2O3 Nanomaterial Catalysed Green and Efficient One Pot Three Component Synthesis of Tetrahydrobenzo[b]pyran

Abstract:The present work reports the hydrothermal synthesis of Fe doped gallium oxide nanoparticles and its characterization by IR, XRD, SEM, and EDX techniques. The characterization of Fe doped gallium oxide nanomaterial reveals the 18.58 nm particle size with monoclinic phase. The catalytic activity of nanomaterial was efficiently assessed for one-pot domino Knoevenagel and Michael's addition of different aldehydes, dimedone, and malononitriles to give tetrahydrobenzo [b] pyran derivatives. The remarkable features associated with this green protocol are good to excellent product yields (60-94%), non-chromatographic purification of product, shorter reaction time, and easy work up. The reusability and non-toxic nature of this nanomaterial catalyst escalate the importance of this work.

One-Pot Synthesis of 1,8-Dioxodecahydroacridines using Ag-TiO2 Nanocomposite as a Mild and Heterogeneous Catalytic System

Abstract:Ag-TiO2 nanocomposite is reported to be an efficient, active, and benign recyclable catalyst for highly efficient synthesis of 1,8-dioxodecahydroacridine derivatives from dimedone, aromatic aldehydes, and several anilines or ammonium acetate in ethanol as a solvent at room temperature in a short reaction time and suitable yield. This catalyst is effortlessly recycled by simple filtration and can be reused up to five times with only a negligible loss in its catalytic effectiveness. Low catalyst loading, cost-effectively mild conditions, non-chromatographic purification of target compounds, excellent atom economy, informal procedure, use of a cheaply accessible nanocomposite catalyst, and recyclability of the catalyst are all significant benefits of this method. AFM analysis is performed to confirm the structure, topography, and morphology of Ag-TiO2 nanocomposite. 1,8-dioxodecahydroacridine derivatives having natural significance possess a wide range of pharmacological activities; for instance, antibacterial, antimalarial, anticancer, and mutagenic properties. In terms of the distinctions between aldehydes and anilines, this approach offers a wide range of applications.

Novel Indoline Spiro Derivatives As Anticancer Agents; Design, Synthesis, Molecular Docking Studies, and ADME Evaluation

Under catalyst-free conditions, an environmentally friendly synthesis of a class of spiropyrane, spiropyranopyrazole, spirobenzofurane, spirobenzofuropyrazole, spirooxadiazolidine, spiro-triazolooxadiazole, spirotriazole, and spirophenanthrene from isatin and different reagents was designed, synthesized, and evaluated for their anticancer activities. Compounds 3, 4, and 9 were formed via a one-pot three-component fusion, and the process of synthesis was interpreted using Knoevenagel condensation, Michael addition, and intramolecular cyclization. The technique of preparation has important benefits such as simple reaction conditions, an easy work-up method, simple separation, and nonchromatographic purification of the products. The 1H, 13C-NMR, and mass spectra of the investigated compounds (2–10) were estimated and matched rather well with the experimental results. The National Cancer Institute (NCI, Bethesda, USA) examined all produced derivatives and found that compound 3 had high anti-cancer cell line activity against non-small cell lung-HCI-H522 (GI% = 93.52%) and melanoma-LOX IMVI (GI%=71.63%). Compounds 7 and 8 also showed inhibitory action, with mean GI% ranging from 9.63% to 35.90%. While Compound 10 demonstrated efficacy against a variety of cell lines representing multiple tumor subpanels, with GI% equal to or more than 40%. Docking experiments with Tyrosine Kinase (PDB ID: 2J5F) were carried out to validate NCI findings. In silico investigations revealed that the majority of the produced spiro compounds satisfied Lipinski’s criteria.

Fe3O4‐supported sulfonated graphene oxide as a green and magnetically separable nanocatalyst for synthesis of 2-amino-3-cyano-4H-chromene derivatives and their in-silico studies

Under ultrasound irradiation, 17 examples of 2-Amino-3-cyano-4H-chromene derivatives were prepared via one-pot three components domino Knoevenagel–Michael condensation reaction of aliphatic/aromatic/heterocyclic aldehydes, malononitrile, and α-naphthol/β–naphthol/resorcinol in the presence of Fe3O4‐supported sulfonated graphene oxide as a green and magnetically separable nanocatalyst in H2O: EtOH (1:1) solvent system. FT-IR, TGA, SEM, and XRD were used to evaluate the catalyst. The current protocol is appealing because of high atom economy (95%), excellent yields (88-95%), its short reaction time, waste-free conditions, cost-effectiveness, use of a nontoxic solvent, lack of high temperature for reflux, non-chromatographic purification of products, recyclability of catalyst, etc. In-silico studies were conducted on the selected proteins DNA gyrase (1KZN) and CYP51 (4WMZ) to study the docking interactions with highest docking scores 4h (−8.8 kcal/mol) and 4e (−10.1 kcal/mol), respectively. ADME and Toxicity analysis of docked compounds and reference drugs were also done. Highlights Room temperature and ultrasound assisted three-component synthesis Synthesis of biological important 4H-chromene derivatives in H2O: EtOH (1:1) solvent High yields of products (88–95%) within rapid reaction time (10–15 min). High atom economy 95%. Avoid of column chromatography In-silico studies Easy and fast work up Magnetically separable and reusable catalyst.

Novel biocatalytic strategy of levan: His-ELP-intein-tagged protein purification and biomimetic mineralization

Here a versatile fusion tag composed of His-tag, intein, and elastin-like polypeptide (ELP) tag was prepared for the first time to be fused with levansucrase SacB to construct a recombinant His-ELP-intein-SacB (HEIS) protein to realize nonchromatographic purification of SacB. The efficient biomimetic mineralization of CaHPO4 and HEIS-based hybrid-hydrangea (CaHPO4-HEIS-HH) with good reusability, excellent storage stability and 254.3% improved relative levan yield was prepared with the biomimetic mineralization method. Additionally, the CaHPO4-HEIS-HH showed outstanding operation activity when catalyzing sucrose in solution and up to 75% sucrose conversion rate in fruit juices. The mechanism of biomimetic mineralization was analyzed to show that the HEIS protein might serve as a “binder” to assemble the nanoflakes during biomimetic mineralization. The CaHPO4-HEIS-HH was applicable for efficient production of the levan-type prebiotic polysaccharides, and this approach should be highly valuable for nonchromatographic purification and convenient preparation of various encapsulated enzymes for more efficient catalysis.

Solution design to extend the pH range of the pH-responsive precipitation of a CspB fusion protein

Cell surface protein B (CspB) from Corynebacterium glutamicum has been developed as a reversible pH-responsive tag for protein purification. CspB fusion proteins precipitate at acidic pH, after that they completely dissolve at neutral pH. This property has been used in a non-chromatographic protein purification method named pH-responsive Precipitation-Redissolution of CspB tag Purification (pPRCP). However, it is difficult to apply pPRCP to proteins that are unstable under acidic conditions. In an effort to shift the precipitation pH to a milder range, we investigated the solution conditions of CspB-fused Teriparatide (CspB50TEV-Teriparatide) during the process of pH-responsive precipitation using pPRCP. The purified CspB50TEV-Teriparatide in buffer without additives precipitated at pH 5.3. By contrast, CspB50TEV-Teriparatide in buffer with 0.5 M Na2SO4 precipitated at pH 6.6 because of the kosmotropic effect. Interestingly, the pH at which precipitation occurred was independent of the protein concentration. The precipitated CspB50TEV-Teriparatide was fully redissolved at above pH 8.0 in the presence or absence of salt. The discovery that proteins can be precipitated at a mild pH will allow pPRCP to be applied to acid-sensitive proteins.

Non-Chromatographic Purification of Synthetic RNA Using Bio-Orthogonal Chemistry.

Solid-phase synthesis of RNA oligonucleotides over 100 nt in length remains challenging due to the complexity of purification of the target strands from the failure sequences. This article describes a non-chromatographic procedure that will enable routine solid-phase synthesis and purification of long RNA strands. The optimized five-step process is based on bio-orthogonal inverse electron demand Diels-Alder chemistry between trans-cyclooctene (TCO) and tetrazine (Tz), and entails solid-phase synthesis of RNA on a photo-labile support. The target oligonucleotide strands are selectively tagged with Tz while on-support. After photocleavage from the solid support, the target oligonucleotide strands can be captured and purified from the failure sequences using immobilized TCO. The approach can be applied for purification of 76-nt long tRNA and 101-nt long sgRNA for CRISPR experiments. Purity of the isolated oligonucleotides should be evaluated using gel electrophoresis, while functional fidelity of the sgRNA should be confirmed using CRISPR-Cas9 experiments. © 2021 Wiley Periodicals LLC. Basic Protocol: Five-step non-chromatographic purification of synthetic RNA oligonucleotides Support Protocol 1: Synthesis of the components that are required for the non-chromatographic purification of long RNA oligonucleotides. Support Protocol 2: Solid-phase RNA synthesis.

Choline Chloride/Glycerol Promoted Synthesis of 3,3-Disubstituted Indol- 2-ones

Objective:: 3,3-Disubstituted indol-2-one derivatives have wider applications in pharmaceuticals and they are key intermediates for the synthesis of many kinds of drug candidates. The development of an efficient and practical method to prepare this class of compound is highly desirable from both environmental and economical points of views. Methods:: In order to establish an effective synthetic method for preparing 3,3-disubstituted indol- 2-one derivatives, the bis-condensation reaction of isatin and 1H-indene-1,3(2H)-dione was selected as a model reaction. A variety of natural deep eutectic solvents (NADESs) were prepared and used for this reaction. The generality and limitation of the established method were also investigated. Results:: It was found that model reaction can be carried out in natural deep eutectic solvent (NADES) based on choline chloride (ChCl) at 80°C under microwave irradiation. This protocol with a broad substrate applicability afforded various 2,2'-(2-oxoindoline-3,3-diyl)bis(1H-indene- 1,3(2H)-dione) derivatives in high yields. Conclusion:: A simple and efficient procedure has been developed for synthesis of 2,2'-(2-oxoindoline- 3,3-diyl)bis(1H-indene-1,3(2H)-dione), spiro[indoline-3,7'-pyrano[5,6-c:5,6-c']dichromene]- 2,6',8'-trione, and spiro[indoline-3,9'-xanthene]trione via bis-condensation between isatin with 1,3- indandione, 4-hydroxycoumarin or 1,3-cyclohexanedione in natural deep eutectic solvent (NADES) based on choline chloride (ChCl) and glycerol (Gl) under microwave irradiation. The salient features of this protocol are avoidance of any additive/catalyst and toxic organic solvent, clean reaction profiles, non-chromatographic purification procedure, and high to excellent yield. Furthermore, the use of NADES as green reaction medium reduces burden on environment and makes the present method environmentally sustainable.

Water extract of pomegranate ash as waste-originated biorenewable catalyst for the novel synthesis of chiral tert‑butanesulfinyl aldimines in water

• Biorenewable waste-derived base as catalyst in water. • Highly sustainable synthesis of chiral tert ‑butanesulfinyl aldimines. • Non-chromatographic purification of products. • Fair reusability of the renewable catalyst and multi-gram scale viability. The renewable materials catalyzed reactions in aqueous media is urgently needed and highly fascinating task in the current state of organic synthesis. Here, we report a novel and sustainable protocol for the biorenewable, waste-originated water extract of pomegranate ash (WEPA) catalyzed condensation reaction of tert ‑butanesulfinamides and aldehydes in water to produce chiral tert ‑butanesulfinyl aldimines ( t BSAIs) in high yields. The products are separated by filtration and purified by recrystallization; avoids the extraction and column chromatographic separation steps. The reaction was performed with high yields in several consecutive recycles of the catalyst and medium, and further this method is highly effective for the multi-gram scale synthesis of t BSAIs. The application of biorenewable catalyst, added metal/catalyst free conditions, absence of volatile organic solvents and additives, vast substrate feasibility, economical profiles, easy operation, reusability of the catalyst, large scale viability, non-chromatographic purification of products and tremendous future perspective are the sparkling insights of this development. A novel and versatile protocol has been developed for the synthesis of tert‑butanesulfinyl aldimines using water extract of pomegranate ash (WEPA) as catalyst in water.

Switchable Self-Assembly of Elastin- and Resilin-Based Block Copolypeptides with Converse Phase Transition Behaviors.

Self-assembly of thermally responsive polypeptides into unique nanostructures offers intriguing attributes including dynamic physical dimensions, biocompatibility, and biodegradability for the smart bio-nanomaterials. As elastin-based polypeptide (EBP) fusion proteins with lower critical solution temperature (LCST) are studied as drug delivery systems, EBP block copolypeptides with the resilin-based polypeptide (RBP) displaying an upper critical solution temperature (UCST) have been of great interest. In this study, we report thermally triggered, dynamic self-assembly of EBP- and RBP-based diblock copolypeptides into switched nanostructures with reversibility under physiological conditions. Molecular DNA clones encoding for the EBP-RBP diblocks at different block length ratios were biosynthesized via recursive directional ligation and overexpressed, followed by nonchromatographic purification by inverse transition cycling. Genetically engineered diblock copolypeptides composed of the EBP with an LCST and the RBP with a UCST showed converse phase transition behaviors with both a distinct LCST and a distinct UCST (LCST < UCST). As temperature increased, three phases of these EBP-RBP diblocks were observed: (1) self-assembled micelles or vesicles below both LCST and UCST, (2) whole aggregates above LCST and below UCST, and (3) reversed micelles above both LCST and UCST. In conclusion, these stimuli-triggered, dynamic protein-based nanostructures are promising for advanced drug delivery systems, regenerative medicine, and biomedical nanotechnology.

A straightforward, environmentally beneficial synthesis of spiro[diindeno[1,2-b:2\u2032,1\u2032-e]pyridine-11,3\u2032-indoline]-2\u2032,10,12-triones mediated by a nano-ordered reusable catalyst

A library of new spiro[diindeno[1,2-b:2′,1′-e]pyridine-11,3′-indoline]-2′,10,12-trione derivatives has been prepared in an efficient, one-pot pseudo four-component method mediated by a reusable heterogeneous nano-ordered mesoporous SO3H functionalized-silica (MCM-41-SO3H) catalyst. Excellent yields, short reaction times, as well as convenient non-chromatographic purification of the products and environmental benefits such as green and metal-free conditions constitute the main advantages of the developed synthetic methodology. The obtained fused indole-indenone dyes would be of interest to pharmaceutical and medicinal chemistry. Furthermore, due to their sensitivity to pH changes, they could be used as novel pH indicators.