One-pot Cascade Reaction Research Articles

Carbonyl Olefin Metathesis and Dehydrogenative Cyclization of Aromatic Ketones and gem-Difluoroalkenes.

The beauty of one-pot cascade reaction lies in the efficient disconnection and construction of several bonds in a single reaction flask, without the isolation of any intermediates. Herein, we report the first photoinduced thermally promoted cascade reactions of readily available aromatic ketones and aromatic gem-difluoroalkenes for the synthesis of phenanthrenes which possess potential utility in drug design and materials science. The reaction combines carbonyl-olefin metathesis (cascade photoinduced [2+2] cyclization and thermally controlled retro [2+2] cyclization) and dehydrogenative cyclization (cascade photoinduced conrotatory 6π electrocyclization and collidine-promoted dehydrogenative aromatization) together in one pot. The oxidant-free, acid-free and metal-free reaction shows broad substrate scope and wide functional group tolerance.

Multienzymatic disintegration of DNA-scaffolded magnetic nanoparticle assembly for malarial mitochondrial DNA detection

Early diagnosis of malaria can prevent the spread of disease and save lives, which, however, remains challenging in remote and less developed regions. Here we report a portable and low-cost optomagnetic biosensor for rapid amplification and detection of malarial mitochondrial DNA. Bioresponsive magnetic nanoparticle assemblies are constructed by using nucleic acid scaffolds containing endonucleolytic DNAzymes and their substrates, which can be activated by the presence of target DNA and self-disintegrated to release magnetic nanoparticles for optomagnetic quantification. Specifically, target molecules can induce padlock probe ligation and subsequent one-pot homogeneous cascade reactions consisting of nicking-enhanced rolling circle amplification, DNAzyme-assisted nucleic acid recycling, and strand-displacement-driven disintegration of the magnetic assembly. With an optimized magnetic actuation process for reaction acceleration, a detection limit of 1 fM can be achieved by the proposed biosensor with a total assay time of ca. 90 min and a dynamic detection range spanning 3 orders of magnitude. The robustness of the system was validated by testing target molecules spiked in 5% serum samples. Clinical sample validation was conducted by testing malaria-positive clinical blood specimens, obtaining quantitative results concordant with qPCR measurements.

One-pot cascade reaction coupling a microbial glycosyltransferase to sucrose synthase for high-level production of cinnamyl alcohol mono-glucoside

Cinnamyl alcohol mono-glucoside (rosin), one of the important ingredients in Rhodiola rosea, displays many biological activities. The traditional production of rosin is direct extraction, which suffers from limited availability of natural resources. This study developed an efficient method for the product of cinnamyl alcohol mono-glucoside using a one-pot cascade reaction by a microbial glycosyltransferase UGTBL1 coupled with sucrose synthase (GmSuSy) from Glycine max. By optimizing the conditions of the UGTBL1-GmSuSy coupled reaction, a high yield of cinnamyl alcohol mono-glucoside could be achieved and it showed good compatibility between the microbial glycosyltransferase UGTBL1 and sucrose synthase GmSuSy for cinnamyl alcohol mono-glucoside formation and UDPG regeneration. Using a fed-batch strategy, cinnamyl alcohol mono-glucoside could reach a high titer of 9.96 g/L with a conversion of 90.8 % in the one-pot cascade reaction. This study lays a significant foundation for the enzymatic production of rosin using glycosyltransferase and sucrose synthase-coupled cascade reactions.

Pushing the boundaries of phosphorylase cascade reaction for cellobiose production I: Kinetic model development.

One-pot cascade reactions of coupled disaccharide phosphorylases enable an efficient transglycosylation via intermediary α-d-glucose 1-phosphate (G1P). Such transformations have promising applications in the production of carbohydrate commodities, including the disaccharide cellobiose for food and feed use. Several studies have shown sucrose and cellobiose phosphorylase for cellobiose synthesis from sucrose, but the boundaries on transformation efficiency that result from kinetic and thermodynamic characteristics of the individual enzyme reactions are not known. Here, we assessed in a step-by-step systematic fashion the practical requirements of a kinetic model to describe cellobiose production at industrially relevant substrate concentrations of up to 600 mM sucrose and glucose each. Mechanistic initial-rate models of the two-substrate reactions of sucrose phosphorylase (sucrose + phosphate → G1P + fructose) and cellobiose phosphorylase (G1P + glucose → cellobiose + phosphate) were needed and additionally required expansion by terms of glucose inhibition, in particular a distinctive two-site glucose substrate inhibition of the cellobiose phosphorylase (from Cellulumonas uda). Combined with mass action terms accounting for the approach to equilibrium, the kinetic model gave an excellent fit and a robust prediction of the full reaction time courses for a wide range of enzyme activities as well as substrate concentrations, including the variable substoichiometric concentration of phosphate. The model thus provides the essential engineering tool to disentangle the highly interrelated factors of conversion efficiency in the coupled enzyme reaction; and it establishes the necessary basis of window of operation calculations for targeted optimizations toward different process tasks.

One-Pot Biocatalytic Synthesis of rac-Syringaresinol from a Lignin-Derived Phenol.

The drive for a circular bioeconomy has resulted in a great demand for renewable, biobased chemicals. We present a one-pot biocatalytic cascade reaction for the production of racemic syringaresinol, a lignan with applications as a nutraceutical and in polymer chemistry. The process consumes dihydrosinapyl alcohol, which can be produced renewably from the lignocellulosic material. To achieve this, a variant of eugenol oxidase was engineered for the oxidation of dihydrosinapyl alcohol into sinapyl alcohol with good conversion and chemoselectivity. The crystal structure of the engineered oxidase revealed the molecular basis of the influence of the mutations on the chemoselectivity of the oxidation of dihydrosinapyl alcohol. By using horseradish peroxidase, the subsequent oxidative dimerization of sinapyl alcohol into syringaresinol was achieved. Conditions for the one-pot, two-enzyme synthesis were optimized, and a high yield of syringaresinol was achieved by cascading the oxidase and peroxidase steps in a stepwise fashion. This study demonstrates the efficient production of syringaresinol from a compound that can be renewed by reductive catalytic fractionation of lignocellulose, providing a biocatalytic route for generating a valuable compound from lignin.

Interfacing Whole Cell Biocatalysis with a Biocompatible Pictet-Spengler Reaction for One-Pot Syntheses of Tetrahydroisoquinolines and Tryptolines.

Biocatalytic processes are highly selective and specific. However, their utility is limited by the comparatively narrow scope of enzyme-catalysed transformations. To expand product scope, we are developing biocompatible processes that combine biocatalytic reactions with chemo-catalysis in single-flask processes. Here, we show that a chemocatalysed Pictet-Spengler annulation can be interfaced with biocatalysed alcohol oxidation. This two-step, one-pot cascade reaction converts tyramine and aliphatic alcohols to tetrahydroisoquinoline alkaloids in aqueous buffer at mild pH. Tryptamine derivatives are also efficiently converted to tryptolines. Optimization of stoichiometry, pH, reaction time, and whole-cell catalyst deliver the tetrahydroisouinolines and tryptolines in >90 % and >40 % isolated yield, respectively, with excellent regioselectivity.

Highly active and recyclable immobilized multiple enzymes for one-pot enantioselective cascade reactions: Synthesis of (R)- and (S)-α-amino acids from racemic α-hydroxy acids

Cascade biotransformation of racemic alcohols to enantiopure amines is highly wanted in pharmaceutical manufacturing but requires green and efficient solution. Here we developed the first immobilized enzyme-based approach for this transformation, being cleaner and more productive than whole-cells biocatalysis, and more economic and higher-yielding than using isolated enzymes. As demonstration, the conversion of racemic mandelic acids to high-value (R)- or (S)-phenylglycines was achieved by immobilized enantioselective alcohol oxidase, racemase, catalase, and (S)- or (R)-transaminase. Co-immobilization of the four enzymes on Ni-NTA functionalised carriers gave high enzyme loadings (192–195 mg enzyme/g carrier), loading efficiencies (97–98%), and free enzyme activities (107–113%). Immobilized enzymes transformed racemic mandelic acids to the corresponding four (S)-phenylglycines in 91–99% ee and 82–95% yields or five (R)-phenylglycines in 93–99% ee and 83–94% yields. These catalysts showed good recyclability, retaining 86–98% productivities in the fifth reaction cycles.

Dense Ru single-atoms integrated with sulfoacids for cellulose valorization to isosorbide

Metal-acid bifunctional catalysts are the unity of two opposites (metal-acid repelling) for cellulosic biomass valorization to isosorbide. It is challenging to improve the selectivity of metal hydrogenation catalysts and their synergism with acids for catalytic hydrolysis and dehydration to achieve substantial isosorbide. Herein, dense Ru single-atoms (10.1 wt% of Ru SAs) are anchored on sulfoacid-functionalized hollow mesoporous carbon shells, designed by assembling silica and 8-hydroxyquinoline-modified chitosan (HQ-CTS) through in situ Stöber templating strategy before pyrolysis and acid treatment. Based on X-ray absorption fine structure and computational modeling results, the structure of Ru SAs is determined as RuN4, which is more selective for a transitional glucose hydrogenation to sorbitol than Ru001 of Ru clusters. A lower-energy barrier of 1.21 (0.72) eV is delivered over RuN4 (Ru001) for glucose hydrogenation (isomerization). These Ru SAs are integrated with sulfoacids (SO3H) but resistent against acids, rendering enhanced isosorbide yield in water as compared to Ru clusters, via a one-pot cascade reaction under harsh conditions (220 °C, 6 MPa H2). The elaborately fabricated dense Ru SAs and sulfoacids, achieved by varying the addition time of HQ-CTS during the in situ Stöber templating process, improve the synergism of glucose hydrogenation with cellulose hydrolysis and sorbitol dehydration. This study provides a new idea for rational design of high-performance metal-acid bifunctional catalysts toward one-pot conversion of cellulose to isosorbide.

Efficient synthesis of 2-benzofuranyl C-glycosides by one-pot cascade reaction of sugar alkynes and substituted 2-iodophenols

2-Benzofuranyl C-glycosides were synthesized in good to excellent yields by one-pot cascade reaction of terminal sugar alkynes and substituted 2-iodophenols. The products have wide structural diversity and potential biological activity. This new synthetic method is general, mild, and efficient. Thirty-seven examples have been given. The structurally diverse terminal sugar alkynes included pyranosides, furanosides, and acyclic sugars with sensitive and bulky protecting groups. The substituted 2-iodophenols contained electron-donating, electron-withdrawing, and electron-neutral substituents. The mechanism for the formation of the products has been proposed.

Balancing Activity and Stability in Halogen-Bonding Catalysis: Iodopyridinium-Catalyzed One-Pot Synthesis of 2,3-Dihydropyridinones.

A one-pot cascade reaction for 2,3-dihydropyridinone synthesis was accomplished with 3-fluoro-2-iodo-1-methylpyridinium triflate as the halogen bond catalyst. The desired [4+2] cycloaddition products, bearing aryl, heteroaryl, alkyl, and alicyclic substituents, were successfully furnished in 28-99% yields. Mechanistic investigations proved that a strong halogen-bonding interaction forged between the iodopyridinium catalyst and imine intermediate was essential to dynamically masking the vulnerable C-I bond on the catalyst and accelerating the following aza-Diels-Alder reaction.

Cu(II)-Catalyzed Cascade of N-Phenyl-o-phenylenediamine with Benzaldehyde: One-Step Direct Construction of 2-(1-Phenyl-1H-benzo[d]imidazol-2-yl)phenols.

A practical protocol for the construction of hydroxylated 2-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenols (PBIs) from N-phenyl-o-phenylenediamine with benzaldehydes was developed. The cascade reaction was enabled by heating a mixture of the two substrates in the presence of air as an oxidant and anhydrous Cu(OAc)2 as a catalyst in dimethyl sulfoxide, and a diverse series of PBIs were synthesized in moderate to good yields (69-81%). Furthermore, the synthesis of the PBIs was enabled via a one-pot cascade reaction that proceeded through subsequent dehydration condensation, intramolecular cyclization, and aromatic C-H hydroxylation. This protocol can be used for the synthesis of hydroxylated PBI via a one-pot annulation C-H hydroxylation reaction rather than through a series of multistep reactions, which provides the possibility of further modification.

Fully Biocatalytic Rearrangement of Furans to Spirolactones.

A multienzymatic pathway enables the preparation of optically pure spirolactone building blocks. In a streamlined one-pot reaction cascade, the combination of chloroperoxidase, an oxidase, and an alcohol dehydrogenase renders an efficient reaction cascade for the conversion of hydroxy-functionalized furans to the spirocyclic products. The fully biocatalytic method is successfully employed in the total synthesis of the bioactive natural product (+)-crassalactone D, and as the key module in a chemoenzymatic route yielding lanceolactone A.

Mixtures of Acid- and Base-Functionalized Microparticles for One-Pot Cascade Reaction.

This study reports on the synthesis of surface-protected acid and base microparticles via surfactant-free emulsion polymerization. The protective layer allows to form particle mixtures with both colloidal catalysts that show excellent performance in a well-established model cascade reaction involving an acid-catalyzed deacetalization and a subsequent base-catalyzed Knoevenagel condensation. Compared to nanoreactors that contain both catalysts, the colloidal mixture shows comparable reaction kinetics despite the local separation of both catalysts onto separate particles. Since the synthesis of individual microparticles requires less steps, is scalable, and more versatile in terms of catalyst variation, colloidal mixtures are certainly an alternative to multifunctional nanoreactors, making them attractive for practical applications.

Copper-catalysed one-pot cascade reaction strategy for the synthesis of benzoxazole-2-acrylic acid and benzoxazole-2‑propanoic acid derivatives

A Cu-catalysed cascade strategy has been developed to synthesize benzoxazole-2-acrylic acid and benzoxazole-2‑propanoic acid derivatives in one pot by reacting 2-bromoaniline with maleic anhydride or succinic anhydride. The cascade cyclic anhydride ring opening followed by O-arylation reaction afforded the products in very good yields.

Biocatalytic Synthesis of Homochiral 2-Hydroxy-4-butyrolactone Derivatives by Tandem Aldol Addition and Carbonyl Reduction.

Chiral 2-hydroxy acids and 2-hydroxy-4-butyrolactone derivatives are structural motifs often found in fine and commodity chemicals. Here, we report a tandem biocatalytic stereodivergent route for the preparation of these compounds using three stereoselective aldolases and two stereocomplementary ketoreductases using simple and achiral starting materials. The strategy comprises (i) aldol addition reaction of 2-oxoacids to aldehydes using two aldolases from E. coli, 3-methyl-2-oxobutanoate hydroxymethyltransferase (KPHMT Ecoli ), 2-keto-3-deoxy-l-rhamnonate aldolase (YfaU Ecoli ), and trans-o-hydroxybenzylidene pyruvate hydratase-aldolase from Pseudomonas putida (HBPA Pputida ) and (ii) subsequent 2-oxogroup reduction of the aldol adduct by ketopantoate reductase from E. coli (KPR Ecoli ) and a Δ1-piperidine-2-carboxylate/Δ1-pyrroline-2-carboxylate reductase from Pseudomonas syringae pv. tomato DSM 50315 (DpkA Psyrin ) with uncovered promiscuous ketoreductase activity. A total of 29 structurally diverse compounds were prepared: both enantiomers of 2-hydroxy-4-butyrolactone (>99% ee), 21 2-hydroxy-3-substituted-4-butyrolactones with the (2R,3S), (2S,3S), (2R,3R), or (2S,3R) configuration (from 60:40 to 98:2 dr), and 6 2-hydroxy-4-substituted-4-butyrolactones with the (2S,4R) configuration (from 87:13 to 98:2 dr). Conversions of aldol adducts varied from 32 to 98%, while quantitative conversions were achieved by both ketoreductases, with global isolated yields between 20 and 45% for most of the examples. One-pot one-step cascade reactions were successfully conducted achieving isolated yields from 30 to 57%.

Cu-Catalyzed Decarboxylative Annulation of N-Phenylglycines with Maleimides: Synthesis of 1H-Pyrrolo[3,4-c]quinoline-1,3(2H)-diones

A novel protocol for the construction of functionalized 1H-pyrrolo[3,4-c]quinoline-1,3(2H)-diones (PQLs, 3) from N-phenylglycines and maleimides was developed. The cascade reaction was enabled by heating a mixture of the two substrates in the presence of di-tert-butyl peroxide (DTBP) as an oxidant and anhydrous CuBr as a catalyst in chlorobenzene. Consequently, a diverse series of PQLs 3 were synthesized in moderate-to-good yields (43-73%). The synthesis of the PQLs was enabled via a one-pot cascade reaction that proceeded through subsequent oxidative decarboxylation, 1,2-addition, intramolecular cyclization, tautomerization, and aromatization reactions. This protocol can be used for the synthesis of functionalized PQLs via a one-pot oxidative decarboxylation annulation reaction rather than through a series of multistep reactions, making it suitable for both combinatorial and parallel syntheses of PQLs.

Bifunctional zirconium-based metal-organic frameworks as chemoselective catalysts for the synthesis of γ-valerolactone from furfural via a one-pot cascade reaction

The transformation of lignocellulosic biomass to platform compounds (γ-valerolactone, GVL) was a significant component in biomass development. Herein, sulfonated Zr-based metal-organic frameworks (MOF-808), a bifunctional heterogeneous catalyst with Lewis and Bronsted acid sites, were prepared to catalyze the one-pot cascade reaction of furfural (FUR) to GVL. The successful modification of the sulfonic group on MOF-808 was substantiated by multiple characterization methods. By adjusting the sulfuric acid concentration to balance the Lewis acid and Bronsted acid sites of the catalyst, S-808–2.37 was confirmed as the preferred catalyst and a 60.4 % GVL yield was achieved with 99.1 % carbon balance under the optimal conditions. Moreover, the 72.8 % GVL yield reached in the 40x magnification experiment also boded well for the catalyst’s application potential. The work in this paper opened up new perspectives for the application of MOF-808 porous materials in the field of selective catalytic conversion of biomass involving multi-step reactions.

Multienzyme Synthesis of Glycyrrhetic Acid 3-O-mono-β-d-glucuronide by Coupling UGT73F15 to UDP-Glucuronic Acid Regeneration Module

Glycyrrhetic acid 3-O-mono-β-d-glucuronide (GAMG), a rare and innovative compound in licorice, exhibits high-potency sweetness and improved physiological activities. However, low amounts of GAMG from plants cannot meet the demands of growing markets. In this study, an efficient one-pot multienzyme cascade reaction for GAMG biosynthesis was constructed using a coupled catalysis of glycosyltransferase and uridine 5′-diphosphate (UDP) glucuronic acid (GlcA) regeneration system. The Glycyrrhiza uralensis glycosyltransferase UGT73F15 was expressed in Escherichia coli BL21 (DE3). The optimal reaction conditions of UGT73F15 were found to be pH 7.5 and 35 °C. The catalytic efficiency (kcat/Km) for glycyrrhetic acid (GA) was 2.14 min−1 mM−1 when using UDP-GlcA as sugar donor. To regenerate costly UDP-GlcA, the one-pot multienzyme cascade reaction including UGT73F15, sucrose synthase, UDP-glucose dehydrogenase, and lactate dehydrogenase was adopted to synthesize GAMG from GA on the basis of the UDP-GlcA regeneration system. By optimizing the cascade reaction conditions, the GAMG production successfully achieved 226.38 mg/L. Our study developed an economical and efficient one-pot multienzyme cascade method for facile synthesis of GAMG and other bioactive glucuronosides.

One-pot sonochemical synthesis and in silico/in vitro antitubercular evaluation of 1-methyl-3-propyl-1H-pyrazole containing polynuclear fused N-heteroarenes

A series of molecules containing the fragment based on 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide were explored as the potential inhibitors of chorismate mutase (or CM that plays an important role in the survival of bacteria). These molecules were evaluated in silico via their docking at the interface site of MtbCM (PDB: 2FP2). Prompted by the promising docking results the ultrasound assisted one-pot synthesis of target molecules i.e. 6-arylpyrazolo[4′,3′:4,5]pyrimido[2,1-a]isoquinolin-8(9H)-one derivatives were undertaken. The methodology involved Sonogashira coupling of 2-iodobenzaldehyde with a terminal alkyne to afford the 2-alkynylbenzaldehyde intermediate in situ that on Yb(III)-catalyzed sequential reaction with 4-amino-1-methyl-3-propyl-1H-pyrazole-5-carboxamide afforded the desired product in good to acceptable yield. To build a small library of compounds, a range of terminal alkynes as well as 2-iodobenzaldehydes were employed and the one-pot cascade reaction proceeded well in all these cases. The strategy was also used to prepare 6-aryl-8H-isoquinolino[1,2-b]quinazolin-8-ones. Three derivatives i.e. 4b, 4h and 4l that participated in good interaction with MtbCM (including a common H-bond with SER70) in silico with the docking score in the range -91 to -84 kcal/mol, exhibited encouraging (60–67%) inhibition at 10 µM in vitro. Further, a brief SAR within the series and in silico ADME prediction for best active compounds are presented. The compound 4l seemed to be of further interest form the view point of discovery and development of new anti-tubercular agents. 2009 Elsevier Ltd. All rights reserved.

One-pot sequential cascade reaction for selective gluconic acid production from cellulose photobiorefining.

We demonstrate the feasibility of cellulose photobiocatalytic conversion with >75% cellulose conversion and >75% gluconic acid selectivity from converted glucose. This process is realized via a one-pot sequential cascade reaction by cellulase enzymes and a carbon nitride photocatalyst that can realize selective glucose photoreforming into gluconic acid. Cellulase enzymes breakdown cellulose into glucose, which will subsequently be converted into gluconic acid by essential oxidative species (˙O2- and ˙OH) via a selective photocatalysis process with simultaneous H2O2 formation. This work demonstrates a good example to realize direct cellulose photobiorefining into value-added chemicals via the photo-bio hybrid system.