Functional Group Transformations Research Articles

Modular Click Assembly DNA-Encoded Glycoconjugate Libraries with on-DNA Functional Group Transformations.

Carbohydrates are an important class of naturally active products and play vital roles in regulating various physiological activities. To meet the demand for carbohydrate-based libraries used for the identification of potential drug candidates for pharmaceutical-related targets, we developed a set of on-DNA protocols to construct the DNA-encoded glycoconjugates, including Seyferth-Gilbert homologation, anomeric azidation, and CuAAC cyclization. These on-DNA chemistries enable the generation and modification of DNA-linked glycosyl compounds with good conversions and broad substrate scope. Finally, three DNA-linked glycoconjugate libraries were successfully generated to demonstrate their applicability and feasibility in library preparation.

An Intramolecular Umpolung Cascade Kukhtin-Ramirez Reaction/Michael Addition-Initiated Cyclization: Stereoselective Synthesis of Tetrasubstituted Cyclopropane Fused 1-Indanones.

Herein, we disclose a fascinating highly stereoselective P(NMe2)3 mediated intramolecular deoxygenative umpolung cascade Michael addition-initiated cyclopropanation with a diverse substrate adaptability. This methodology creates a new horizon for expedient access to valuable 6,5,3-fused scaffolds having an all-carbon quaternary stereocenter via Kukhtin-Ramirez (K-R) adduct formation, with excellent diastereoselectivity and yields under metal-free ambient conditions. A few functional group transformations have also been performed successfully. Additionally, an asymmetric catalytic attempt using (R)-(+)-H8-BINOL has delivered good enantioselectivity.

Solid‐Supported Catalysts for Organic Functional Group Transformations

AbstractDesign of solid‐supported metal catalysts (SSMCs) has made an increasingly important contribution to heterogeneous catalysis in terms of fundamental understanding and technological applications. For instance, industrial use of supported catalysts for oxidation, reduction, and C−C bond formation reactions is highly prevalent. The reason behind this is that such catalysts are economical, have high thermal stability, dispersion, high exposed surface area, and above all, high reusability (up to multiple subsequent cycles). Such characteristics make supported catalysts ideal for green synthesis. However, unlike homogeneous catalysis, heterogeneous catalysis is widely applied in crude oil refining, the pharmaceutical industry, water purification, natural product synthesis, and environmental catalysis. Carbon‐carbon bond formation reactions are frequently used in the organic synthesis using SSMCs. SSMCs are attractive to synthetic chemists due to their easy recovery and excellent stability compared to unsupported metal catalysts. However, the major drawback of SSMCs is related to metal sintering at elevated temperatures caused by weak interactions between the metal and solid support in SSMCs. This review highlights major advancements in SSMCs. Three commonly reported solid supports for metal catalysts, such metal oxides, carbonaceous materials, and polymeric compounds, are discussed. Moreover, a series of thermo‐ and photocatalyzed reactions, such as hydrogenation, carbon‐carbon bond formation, oxidation reactions and multicomponent reactions and the effect of variable supports towards activity and selectivity are demonstrated.

A Mild Method for the Replacement of a Hydroxyl Group by Halogen: 4. Practical Synthesis of Cyclic β-Halovinylketones under Neutral Conditions

AbstractThe replacement of a hydroxyl group by a halogen is a pivotal organic functional group transformation. Existing procedures often require acidic conditions or lack sustainability and atom economy. We have previously shown that tetramethyl-α-haloenamines (TMXE) or 2,2-dimethyl-1-halo-1-diisopropylamines (DIXE) react with a wide variety of hydroxyl-containing molecules to yield the corresponding halides under very mild conditions and with high atom economy. We now show that the deoxyhalogenation reactions of the enol tautomers of cyclic1,3-diketones and of 2-hydroxymethylene cycloketones can also be performed with TMCE or DIXE to yield β-halo-α,β-unsaturated ketones in excellent yields. The reactions are regioselective and in some cases stereoselective. The reaction is also successful with acetylacetone but the yield is only moderate. β-Ketoesters are not reactive. The method favorably compares to the best existing methods: It is more general, occurs under very mild conditions, which should allow acid-sensitive functional groups such as ketals, esters, ethers, etc., to be tolerated, and, above all, is quite sustainable (no toxic reagents or products).

An Amino Acid‐Based Thixotropic Hydrogel: Tuning of Gel Recovery Time by Mechanical Shaking

AbstractFmoc‐Trp‐OH (Fmoc: N‐fluorenylmethoxycarbonyl; Trp‐OH: L‐Tryptophan) undergone hydrogelation at 50 mM phosphate buffer saline of pH 7.4 with a minimum gelation concentration (MGC) of 0.25 % w/v after 12 to 15 hours. However, the hydrogel formation kinetics can be faster just by mechanical hand shaking of the hydrogelator solution during the hydrogel preparation procedure. The shake hydrogel is thermally and mechanically more stable than the non‐shake hydrogel. These hydrogels have been characterized thoroughly by Tgel estimations, UV‐Vis spectroscopy, Fluorescence spectroscopy, Fourier Transform‐Infra Red (FT‐IR) Spectroscopy, X‐ray diffractions (XRD), Field Emission Scanning Electron Microscopy (FE‐SEM) and rheology. This amino acid‐based hydrogel is thixotropic in nature and interestingly without doping any foreign materials into the hydrogel, the gel reformation kinetics can be faster just by number of times breaking of the hydrogel by mechanical hand shaking followed by keeping the hydrogel glass vial at rest. This holds future promise to develop supramolecular mechanocatalyst for various functional group transformation reactions in water through green and sustainable chemistry pathways.

Temperature-Controlled Divergent Asymmetric Synthesis of Indole-Based Medium-Sized Heterocycles through Palladium Catalysis

The divergent construction of chiral medium-sized rings is an essential but challenging task in organic synthesis. Herein, we report a temperature-controlled catalytic system for the divergent, enantioselective synthesis of different types of medium-sized rings starting from the same substrate set. Enabled by a planar chiral bisphosphine ligand, the palladium-catalyzed (5 + 4) and formal (5 + 2) annulations of cyclic aza-dienes and vinylethylene carbonates proceeded smoothly to afford a broad spectrum of indole-based medium-sized heterocycles in excellent yields with outstanding enantioselectivities. Those products could be further diversified through various functional group transformations. Moreover, mechanistic studies, including control experiments and DFT calculations, shed light on understanding the observed regio- and enantioselectivities of palladium-catalyzed (5 + n) cyclization.

Hydrolysis, Microstructural Profiling and Utilization of Cyamopsis tetragonoloba in Yoghurt

The present study investigates the hydrolysis, microstructural profiling and utilization of guar gum (Cyamopsis tetragonoloba) as a prebiotic in a yoghurt. Guar galactomannans (GG) was purified and partially depolymerized using an acid, alkali and enzyme to improve its characteristics and increase its utilization. The prebiotic potential of hydrolyzed guar gum was determined using Basel and supplemented media. Crude guar galactomannans (CGG), purified guar galactomannans (PGG), base hydrolyzed guar galactomannans (BHGG), acid hydrolyzed guar galactomannans (AHGG) and enzymatic hydrolyzed guar galactomannans (EHGG) were analyzed using scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Yoghurt was prepared with a starter culture and incorporating guar gum, its hydrolyzed forms (0.1, 0.5 and 1%) and Bifidobacterium bifidum. The results showed that PHGG significantly improved the viability of B. bifidum. SEM revealed a significant change in the surface morphology of guar gum after acidic and enzymatic hydrolysis. Enzymatic hydrolysis developed a well-defined framework within guar gum molecules. The XRD pattern of CGG, PGG and AHGG presented an amorphous structure and showed low overall crystallinity while EHGG and BHGG resulted in slightly increased crystallinity regions. FTIR spectral analysis suggested that, after hydrolysis, there was no major transformation of functional groups. The addition of the probiotic and prebiotic significantly improved the physiochemical properties of the developed yoghurt. The firmness, cohesiveness, adhesiveness and syneresis were increased while consistency and viscosity were decreased during storage. In sum, a partial hydrolysis of guar gum could be achieved using inexpensive methods with commercial significance.

Reaction-based energy level modulation of a cyclometalated iridium complex for electrochemiluminescent detection of formaldehyde.

Formaldehyde is a toxic compound present in both the environment and living systems, and its detection is important due to its association with various pathological process. In this study, we report a new electrochemiluminescence (ECL) probe based on a cyclometalated iridium complex (IrHAA) for the selective detection of formaldehyde. The homoallylamine moiety in IrHAA reacts with formaldehyde, undergoing a 2-aza-Cope-rearrangement reaction to form a formyl group. Significant changes in the electronic properties and molecular orbital energies of the iridium complex through the functional group transformation result in enhanced ECL and radiometric phosphorescence changes, enabling the quantitative and selective detection of formaldehyde. The energetic requirements for ECL sensing were investigated, highlighting the importance of the excited state energy for achieving efficient ECL. The sensing mechanism was elucidated using NMR spectroscopy and MALDI-TOF analysis.

Total Synthesis of Ansellone G and Phorbadione.

The first total synthesis of marine sesterterpenoid ansellone G (2) was accomplished. This strategy utilizes the Prins cyclization reaction of a chloro-substituted homoallyl alcohol to synthesize the hydrobenzopyran skeleton. The preintroduction of the chloro groups facilitated the functional group transformation for 2 after constructing the carbon framework. Furthermore, we also successfully synthesized phorbadione (3) by dehydrating the tertiary alcohol. The HIV latency-reversing activity of the synthesized 2, 3, and deacetylated 2 was also evaluated.

Copper-Catalyzed Claisen Rearrangement with AIBN and Allylic Alcohols.

A novel and succinct method for the synthesis of N-cyanomethyl amides from allylic alcohols with AIBN as the nitrile source is developed. Owing to the coordination effect with the copper catalyst, a ketenimine intermediate is formed via couplings of isobutyronitrile radicals. The copper-activated ketenimine could subsequently be intercepted by allylic alcohols and undergo Claisen rearrangement to furnish N-cyanomethyl amides. Further functional group transformations of the N-cyanomethyl amide products are also described.

Fe catalysed transformation of oxygen functional groups on coal based needle coke for sodium storage

The oxygen functional groups (OFGs) on the surface of carbon materials are regarded to be efficient and stable sodium storage sites. Herein, we selected coal-based needle coke (NC) with industrial prospects as raw materials. The C–O contained OFGs without sodium storage activity were transformed to the C=O contained OFGs with sodium storage activity by Fe catalysed transformation. Moreover, the ring graphite domains were induced during the catalytic reaction. Based on the above, a balance state between abundant sodium storage sites and suitable electron distribution was formed on the surface of NC. Therefore, the modified NC showed the reversible capacities of 306 mA h g−1 at 0.05 A g−1 after 100 cycles and 194 mA h g−1 at 2 A g−1 after 1000 cycles. Moreover, reversible potassium storage capacities of 327 mA h g−1 at 0.03 A g−1 after 50 cycles and 99 mA h g−1 at 1 A g−1 after 1000 cycles could also be achieved for the sample. The work provides a reasonable and convenient path to realize the balance between electrochemical active sites and electronic conductivity, and gives a reference for directional oxygen functionalization of carbon materials in the field of energy storage.

Photocatalytic Dissolution of Precious Metals by TiO2 through Photogenerated Free Radicals.

Exploring the pathways for photocatalytic dissolution of precious metals (PMs) is crucial for optimizing recovery. In this work, we systematically investigated the selectivity and solvation effects observed for dissolution by focusing on photocatalysis, precious metals and solvents. By combining transient characterization, reaction kinetics, and density functional theory, we determined that the radicals generated in photocatalysis were the key active species in the entire reaction. The cyano functional group in the solvent was the driving factor for dissolution of gold, and the importance of chlorine radicals for dissolution of platinum group precious metals was further confirmed. In addition, the catalytic properties of different precious metals can promote different transformations of functional groups, leading to selective dissolution. The structures of photocatalytic precious metal leaches also precisely explains the special coordination forms of precious metals and functional group ligands.

Photocatalytic Dissolution of Precious Metals by TiO2 through Photogenerated Free Radicals

AbstractExploring the pathways for photocatalytic dissolution of precious metals (PMs) is crucial for optimizing recovery. In this work, we systematically investigated the selectivity and solvation effects observed for dissolution by focusing on photocatalysis, precious metals and solvents. By combining transient characterization, reaction kinetics, and density functional theory, we determined that the radicals generated in photocatalysis were the key active species in the entire reaction. The cyano functional group in the solvent was the driving factor for dissolution of gold, and the importance of chlorine radicals for dissolution of platinum group precious metals was further confirmed. In addition, the catalytic properties of different precious metals can promote different transformations of functional groups, leading to selective dissolution. The structures of photocatalytic precious metal leaches also precisely explains the special coordination forms of precious metals and functional group ligands.

Urease and β-glucosidase activity enhanced the transformation of functional groups of humin amended by straw and straw-derived biochar

BackgroundOrganic materials carbon is mainly sequestrated in humin. However, the carbon (C) stability of humin with organic materials amendments in different types of soils is mainly affected by organic materials or soil types as well as the enzymatic reaction is important for understanding the C sequestration mechanism of soil.ResultsIn this study, straw and straw-derived biochar were incorporated into three different types of soils. Using 13C nuclear magnetic resonance (NMR) spectroscopy, the structural composition of humin (Hu) was analyzed, along with the urease and β-glucosidase activities. The results showed that biochar amendment enhanced aryl C to 49.63%–76.55% while straw amendments increased O-alkyl C of Hu to 33.99%–51.70%. Two-way ANOVA analysis revealed significant differences in the impact of soil types and treatments on enzyme activities and functional groups of humin. A significant positive correlation was found between β-glucosidase activity and O-alkyl C, phenolic C, and methoxyl C of humin. In addition, urease activity showed a significant positive correlation with alkyl C of humin. Compared to tobacco straw, tobacco straw-biochar amendment increased β-glucosidase activity for 22.01 mg kg−1 d−1, 26.01 mg kg−1 d−1 and 14.01 mg kg−1 d−1 in three types of soils, respectively.ConclusionsThese results showed that β-glucosidase contributed to the transformation of humin functional groups and was influenced by organic materials and soil types, especially the organic materials types. The findings imply that straw or straw-derived biochar application stimulates urease and β-glucosidase activities, which improves the alternation of functional groups of humin in different types of soil.Graphical

Biochar–goethite composites inhibited/enhanced degradation of triphenyl phosphate by activating persulfate: Insights on the mechanism

In this study, the biochar–goethite composites (MBC@FH) were synthesized through co–ball milling and the degradation of triphenyl phosphate (TPhP) was compared in persulfate (PDS) alone system and MBC@FH&PDS systems. The results showed that TPhP can be effectively degraded in PDS alone system and degradation efficiency reached up to 90 % within reaction of 8 h, at a PDS concentration of 10 mM, a reaction temperature of 30 °C and a system pH of 6.12. The obvious degradation can be ascribed to the reactive oxygen species (ROS) generated by self–decompose of PDS, among which 1O2, ∙OH and O2∙− play a major role in the degradation process. Although 350 °C biochar–goethite composites (MBC35@FH) and 800 °C biochar–goethite composites (MBC80@FH) facilitated PDS activation to produce more ROS, the catalytic degradation of TPhP was different in their systems. The degradation of TPhP was inhibited by MBC35@FH due to its stronger adsorption for TPhP, while MBC80@FH promoted TPhP degradation and degradation efficiency was up to 100 % within 6 h. 1O2 and SO4∙− played a stronger degradation role than ∙OH and O2∙− in above systems. The transformation of Fe species, functional groups (oxygen–containing functional groups, pyrrolic nitrogen) and persistent free radicals (PFRs) on the MBC@FH were involved in the PDS activation to produce ROS. Furthermore, MBC80@FH was more capable of activating PDS than MBC35@FH due to its abundant defect sites, larger specific surface area, more PFRs, higher Fe content and stronger electron transfer capability. In addition, seven possible TPhP intermediates were identified and possible degradation pathways of TPhP were proposed accordingly. This study illustrated that not all metallic carbon catalysts are necessarily beneficial for organic contaminants degradation.

Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition.

A convergent strategy for the synthesis of leustroducsins and phoslactomycins has been designed, relying on the synthesis and the coupling of three main fragments. The central fragment was synthesized via a regio-and stereoselective nitroso Diels–Alder reaction with an enol phosphate, followed by reductive cleavage of the phosphate to the ketone 11b. Coupling studies of this fragment with the lactone fragment was accomplished in a stereoselective fashion through a vinyllithium intermediate. An advanced synthetic intermediate was then obtained after functional group transformation.

Coupling-to-diazonium role-convert strategy for 1,3-dimethylbarbituric acid-based dyes and configurational confirmation via NMR/UV–vis spectra

5-Amino-1,3-dimethlybarbituric acid (5-amino-diMeBA), prepared form 1,3-dimethlybarbituric acid (diMeBA) via the functional group transformation strategy, is first used as the diazonium component to produce heterocyclic dyes, in order to expand the existing research objects in this area. Role-convert synthesis has been successfully achieved from a general coupling component diMeBA to a corresponding diazonium unit 5-amnio-diMeBA, and three pyrazolone/pyridone coupled bi-heterocyclic dyes were yielded. There are multiple possible azo/hydrazone tautomers for them since three ortho-carbonyl groups could serve as the protonated sites for active protons. The configurational confirmation depends on the precise location of heterocyclic hydroxyl groups, which could be deduced by comparing the alterations of two characteristic methyl single peaks in diMeBA moiety in the 1H NMR spectra before and after deprotonation. Our results reveal that three bi-heterocyclic dyes adopt the monohydrazone form in pyrazolone with 4-OH-diMeBA and the monohydrazone form in diMeBA with 6-OH-pyridone, respectively. Further UV–Vis spectra have been carried out to compare the delocalized π-conjugated system for them, together with three BA coupled heterocyclic dyes. In addition, solvatochromic and acid-base titration experiments were performed to verify the strength of intramolecular charge transfer within the whole molecules and the monohydrazone configuration for every bi-heterocyclic dye.

4,4‐Difluorospiro[2.2]pentan‐1‐yl – A Fluorinated Substituent To Expand the Synthetic and Medicinal Chemists’ Toolbox

AbstractFunctionalized 4,4‐difluorospiro[2.2]pentan‐1‐yl derivatives are proposed as promising building blocks for synthetic and medicinal chemistry. Scalable, efficient, and diastereoselective approach to their preparation via the difluorocyclopropanation of (2‐methylenecyclopropyl)methanol is developed. Stability of the title scaffolds towards common reaction conditions is confirmed by a series of typical functional group transformations. Physicochemical characteristics (pKa, logP, and aqueous solubility) and structural features of the key 4,4‐difluorospiro[2.2]pentan‐2‐yl derivatives are established and compared with those of non‐fluorinated analog, 2,2‐difluorinated isomer, as well as monocyclic gem‐difluorinated counterparts.

Adsorption behavior of aged polybutylece terephthalate microplastics coexisting with Cd(II)-tetracycline.

Microplastics (MPs) are one of the emerging classes of pollutants that can be infiltrated into any aqueous solutions from disposed toxic metals and antibiotics, further exacerbating the potential biotoxicity of MPs. However, the research on the interaction between MPs and various pollutants is limited. Therefore, in this study, the changes in toxicity of polybutylece terephthalate (PBT) MPs were assessed following adsorption of heavy metals and antibiotics. The adsorption behavior of Cd(II) and tetracycline (TC) on ultraviolet (UV) light-aged PBT was investigated. The results demonstrated that the Cd(II) adsorption behavior could be described by the pseudo-second-order kinetic and Langmuir isothermal models, while the TC adsorption behavior has well fitted using Elovich and Sips models. The whole adsorption process occurred via either external diffusion or internal diffusion. The interactions between aged PBT and pollutants were evaluated under different environmental conditions, such as solution pH and the concentrations of dissolved organic matter and cations. The amounts of Cd(II) and TC adsorbed were higher in the competitive systems than the single solution, which might attribute to the formation of Cd(II)-TC complexes and aged PBT functional group changes. The results of two-dimensional correlation spectroscopy (2D-COS) describes the sequence of functional group transformation during the uptake of Cd(II)-TC by aged PBT in binary systems. These findings identify a strong interaction between aged PBT and contaminants, establishing the potential fate of aged MPs under natural aquatic environment conditions.

Exploring the feasibility and potential mechanism of synergistic enhancement of sludge dewaterability by ultrasonic cracking, chitosan re-flocculation and sludge-based biochar adsorption of water-holding substances

A method based on sludge-based biochar (SBB) skeleton adsorption of water-holding substances coupled with ultrasonic (US) cracking and chitosan (CTS) re-flocculation was proposed to strengthen sludge dewatering. Combined conditioning can greatly improve the sludge dewatering performance, the specific resistance to filtration (SRF), capillary suction time (CST), cake moisture content (MC) of sludge were reduced by 92.98 %, 78.46 %, 16.35 %. By analyzing the Zeta potential, relative hydrophobicity, water distribution, particle size distribution, filtrate organic matter, and extracellular polymeric substances (EPS) composition and structure of sludge, it was found that US, CTS and SBB showed significant synergistic effects. US disintegrated sludge flocs and promoted the transformation of functional groups on EPS, breaking the bond between solid and water molecules, releasing some bound water and intracellular substances, which laid the foundation for SBB to adsorb water-holding substances. CTS reconstituted flocs and crosslinked with protein (PN) to form complexes, which changed the spatial conformation of proteins. SBB adsorbs the water-holding substances such as protein and polysaccharide (PS) released in the outer EPS, promotes the dissolution of inner EPS, further promotes the denaturation and transformation of protein secondary structure, and improves the hydrophobic expression of sludge. Moreover, the combined conditioning reduces the compressibility of sludge and improves the water filtration efficiency. US+CTS+SBB is a green and promising combination technology, which has a certain reference value for sludge deep dehydration.