Efficient copper-catalyzed amination of DNA-conjugated aryl iodides under mild aqueous conditions

Recent synthetic strategies for N-arylation of pyrrolidines: a potential template for biologically active molecules

The chemistry of nitrogen-containing heterocyclic compounds has been a multifaceted area of research for an extended period due to their varied therapeutic and biological significance. N-Aryl pyrrolidine formed by condensation of aryl group with nitrogen atom of pyrrolidine is present in a wide array of compounds. Various significant activities shown by N-arylated pyrrolidine include anti-Alzheimer, antihypoxic, anticancer, plant activator, analgesic effect, and hepatitis C inhibitor. This review summarizes different synthetic approaches, e.g., transition-metal catalyzed and transition-metal-free synthesis, decarboxylation reaction, reductive amination, nucleophilic cyclization, Ullmann-Goldberg amidation, Buchwald-Hartwig reaction, Chan-Evans-Lam coupling, addition to benzyne, multistep reaction, green synthesis, rearrangement reaction, and multicomponent reaction, to afford the derivatives of N-aryl pyrrolidine. It encompasses synthetic strategies documented from 2015 to 2023.

Diversification of Pharmaceutical Manufacturing Processes: Taking the Plunge into the Non-PGM Catalyst Pool

Recent global events have led to the cost of platinum group metals (PGMs) reaching unprecedented heights. Many chemical companies are therefore starting to seriously consider and evaluate if and where they can substitute PGMs for non-PGMs in their catalytic processes. This review covers recent highly relevant applications of non-PGM catalysts in the modern pharmaceutical industry. By highlighting these selected successful examples of non-PGM-catalyzed processes from the literature, we hope to emphasize the enormous potential of non-PGM catalysis and inspire further development within this field to enable this technology to progress toward manufacturing processes. We also present some historical contexts and review the perceived advantages and challenges of implementing non-PGM catalysts in the pharmaceutical manufacturing environment.

Evolution of chemistry and selection technology for DNA-encoded library

DNA-encoded chemical library (DEL) links the power of amplifiable genetics and the non-self-replicating chemical phenotypes, generating a diverse chemical world. In analogy with the biological world, the DEL world can evolve by using a chemical central dogma, wherein DNA replicates using the PCR reactions to amplify the genetic codes, DNA sequencing transcripts the genetic information, and DNA-compatible synthesis translates into chemical phenotypes. Importantly, DNA-compatible synthesis is the key to expanding the DEL chemical space. Besides, the evolution-driven selection system pushes the chemicals to evolve under the selective pressure, i.e., desired selection strategies. In this perspective, we summarized recent advances in expanding DEL synthetic toolbox and panning strategies, which will shed light on the drug discovery harnessing in vitro evolution of chemicals via DEL.

Photoredox-catalysed hydroaminoalkylation of on-DNA N-arylamines

An efficient approach to the photoredox-catalysed hydroaminoalkylation between on-DNA secondary N-substituted (hetero)arylamines and vinylarenes has been developed and explored. The methodology was examined with a broad scope of vinylarenes and secondary arylamines to establish a preferred building block profile for the process. Compatible substrates furnished the desired derivitised amine products in modest to excellent conversions and with minimal or no detectable by-products.

Metal-Free and Open-Air Arylation Reactions of Diaryliodonium Salts for DNA-Encoded Library Synthesis

A successful DNA-encoded library (DEL) will consist of diverse skeletons and cover chemical space as comprehensive as possible to fully realize its potential in drug discovery and chemical biology. However, the lack of versatile on-DNA arylation methods for phenols that are less nucleophilic and reactive poses a great hurdle for DEL to include diaryl ether, a privileged chemotype in pharmaceuticals and natural products. This work describes the use of "substrate activation" approach to address the arylation of DNA-conjugated phenols. Diaryliodonium salt, a highly electrophilic and reactive arylation reagent, is employed as Ar+ sources to ensure highly selective on-DNA arylation of phenols and oximes with both high yields and DNA fidelity. Notably, the new on-DNA arylation reaction can be applied to the late-stage modification of peptides containing tyrosine side-chain and to synthesize DNA-tagged analogues of existing drug molecules such as sorafenib, a known pan-kinase inhibitor. The new on-DNA diaryliodonium salts chemistry affords a greater flexibility in DEL design and synthesis.

Palladium-Mediated Hydroamination of DNA-Conjugated Aryl Alkenes

C-N bond formation is one of the most commonly used reactions in medicinal chemistry. Herein, we report an efficient Pd-promoted hydroamination reaction between DNA-conjugated aryl alkenes and a wide scope of aliphatic amines. The described reactions are demonstrated in good to excellent conversions to furnish C (sp3)–N bonds on DNA. This DNA-compatible transformation has strong potentials for the application into DNA-encoded library synthesis.

DNA-Compatible Diversification of Indole π-Activated Alcohols via a Direct Dehydrative Coupling Strategy

Indole-based diversification is highly desired in the DNA-encoded chemical library construction. Herein, we present a general strategy for on-DNA synthesis of diverse C3-functionalized indole derivatives via indole π-activated alcohol formation followed by direct dehydrative coupling. Highly efficient bond linkages of C-C, C-N, and C-S were achieved to fuse building blocks that are widely commercially available. DNA-encoding compatibility of the method has been further demonstrated to pave an avenue for application in constructing indole-focused three-dimensional libraries.

The expanding reaction toolkit for DNA-encoded libraries

Over the past decade, DNA-encoded libraries (DELs) have emerged as a leading platform for small molecule drug discovery among pharmaceutical companies, biotech companies and academic drug hunters alike. This revolutionary technology has tremendous potential that is yet to be fully realized, as the exploration of therapeutically relevant chemical space is fueled by the ever-expanding repertoire of DNA-compatible reactions used to construct the libraries. Advances in direct coupling reactions, like photo-catalytic cross couplings, unique cyclizations such as the formation of 1,2,4-oxadiazoles, and new functional group transformations are valuable contributions to the DEL reaction toolkit, and indicate where future reaction development efforts should focus in order to maximize the productivity of DELs.

DNA-Encoded Chemistry: Drug Discovery from a Few Good Reactions

Click chemistry, proposed nearly 20 years ago, promised access to novel chemical space by empowering combinatorial library synthesis with a "few good reactions". These click reactions fulfilled key criteria (broad scope, quantitative yield, abundant starting material, mild reaction conditions, and high chemoselectivity), keeping the focus on molecules that would be easy to make, yet structurally diverse. This philosophy bears a striking resemblance to DNA-encoded library (DEL) technology, the now-dominant combinatorial chemistry paradigm. This review highlights the similarities between click and DEL reaction design and deployment in combinatorial library settings, providing a framework for the design of new DEL synthesis technologies to enable next-generation drug discovery.

Diversity-oriented synthesis as a tool to expand the chemical space of DNA-encoded libraries

DNA-encoded libraries (DEL) represent a powerful technology for generating compound collections for drug discovery campaigns, that have allowed for the selection of many hit compounds over last three decades. However, the application of split-and-pool combinatorial methodologies, as well as the limitation imposed by DNA-compatible chemistry, has often brought to a limited exploration of the chemical space, with an over-representation of flat aromatic or peptide-like structures, whereas a higher scaffold complexity is generally associated with a more successful biological activity of the library. In this context, the application of Diversity-Oriented Synthesis, capable of creating sp³-rich molecular entities even starting from simple flat building blocks, can represent an efficient strategy to significantly broaden the chemical space explored by DELs. In this review, we present selected examples of DNA-compatible complexity-generating reactions that can be applied for the generation of DNA-encoded DOS libraries, including: (i) multicomponent reactions; (ii) C-H/C-X functionalization; (iii) tandem approaches; (iv) cycloadditions; (v) reactions introducing privileged elements. Also, selected case studies on the generation of DELs with high scaffold diversity are discussed, reporting their application in drug discovery programs.

Improved Diazo-Transfer Reaction for DNA-Encoded Chemistry and Its Potential Application for Macrocyclic DEL-Libraries

DNA-encoded libraries (DEL) are increasingly being used to identify new starting points for medicinal chemistry in drug discovery. Herein, we discuss the development of methods that allow the conversion of both primary amines and anilines, attached to DNA, to their corresponding azides in excellent yields. The scope of these diazo-transfer reactions was investigated, and a proof-of-concept has been devised to allow for the synthesis of macrocycles on DNA.

C-S Coupling of DNA-Conjugated Aryl Iodides for DNA-Encoded Chemical Library Synthesis

Thioethers have been widely found in biologically active compounds, including pharmaceuticals. In this report, a highly efficient approach to on-DNA construction of thioethers via Cu-promoted Ullmann cross-coupling between DNA-conjugated aryl iodides and thiols is developed. This methodology was demonstrated with medium to high yields, without obvious DNA damage. This reported reaction has strong potential for application in DNA-encoded chemical library synthesis.

Solution-Phase Fmoc-Based Peptide Synthesis for DNA-Encoded Chemical Libraries: Reaction Conditions, Protecting Group Strategies, and Pitfalls

Peptide drug discovery has shown a resurgence since 2000, bringing 28 non-insulin therapeutics to the market compared to 56 since its first peptide drug, insulin, in 1923. While the main method of discovery has been biological display-phage, mRNA, and ribosome-the synthetic limitations of biological systems has restricted the depth of exploration of peptide chemical space. In contrast, DNA-encoded chemistry offers the synergy of large numbers and ribosome-independent synthetic flexibility for the fast and deeper exploration of the same space. Hence, as a bridge to building DNA-encoded chemical libraries (DECLs) of peptides, we have developed substrate-tolerant amide coupling reaction conditions for amino acid monomers, performed a coupling screen to illustrate such tolerance, developed protecting group strategies for relevant amino acids and reported the limitations thereof, developed a strategy for the coupling of α,α-disubstituted alkenyl amino acids relevant to all-hydrocarbon stapled peptide drug discovery, developed reaction conditions for the coupling of tripeptides likely to be used in DECL builds, and synthesized a fully deprotected DNA-decamer conjugate to illustrate the potency of the developed methodology for on-DNA peptide synthesis.

Merging C(sp3)-H activation with DNA-encoding

DNA-encoded library (DEL) technology has the potential to dramatically expedite hit identification in drug discovery owing to its ability to perform protein affinity selection with millions or billions of molecules in a few experiments. To expand the molecular diversity of DEL, it is critical to develop different types of DNA-encoded transformations that produce billions of molecules with distinct molecular scaffolds. Sequential functionalization of multiple C–H bonds provides a unique avenue for creating diversity and complexity from simple starting materials. However, the use of water as solvent, the presence of DNA, and the extremely low concentration of DNA-encoded coupling partners (0.001 M) have hampered the development of DNA-encoded C(sp³)–H activation reactions. Herein, we report the realization of palladium-catalyzed C(sp³)–H arylation of aliphatic carboxylic acids, amides and ketones with DNA-encoded aryl iodides in water. Notably, the present method enables the use of alternative sets of monofunctional building blocks, providing a linchpin to facilitate further setup for DELs. Furthermore, the C–H arylation chemistry enabled the on-DNA synthesis of structurally-diverse scaffolds containing enriched C(sp³) character, chiral centers, cyclopropane, cyclobutane, and heterocycles.

DNA-compatible C(sp³)–H activation reactions of aliphatic carboxylic acids, amides, and ketones were developed for efficient access to DEL synthesis.

Transition-Metal-Mediated Modification of Biomolecules

The site-selective modification of biomolecules has grown spectacularly in recent years. The presence of a large number of functional groups in a biomolecule makes its chemo- and regioselective modification a challenging goal. In this context, transition-metal-mediated reactions are emerging as a powerful tool owing to their unique reactivity and good functional group compatibility, allowing highly efficient and selective bioconjugation reactions that operate under mild conditions. This Minireview focuses on the current state of organometallic chemistry for bioconjugation, highlighting the potential of transition metals for the development of chemoselective and site-specific methods for functionalization of peptides, proteins and nucleic acids. The importance of the selection of ligands attached to the transition metal for conferring the desired chemoselectivity will be highlighted.

An overview of DNA-encoded libraries: A versatile tool for drug discovery

DNA-encoded libraries (DELs) are collections of small molecules covalently attached to amplifiable DNA tags carrying unique information about the structure of each library member. A combinatorial approach is used to construct the libraries with iterative DNA encoding steps, facilitating tracking of the synthetic history of the attached compounds by DNA sequencing. Various screening protocols have been developed which allow protein target binders to be selected out of pools containing up to billions of different small molecules. The versatile methodology has allowed identification of numerous biologically active compounds and is now increasingly being adopted as a tool for lead discovery campaigns and identification of chemical probes. A great focus in recent years has been on developing DNA compatible chemistries that expand the structural diversity of the small molecule library members in DELs. This chapter provides an overview of the challenges and accomplishments in DEL technology, reviewing the technological aspects of producing and screening DELs with a perspective on opportunities, limitations, and future directions.

Water-Compatible Cycloadditions of Oligonucleotide-Conjugated Strained Allenes for DNA-Encoded Library Synthesis

DNA-encoded libraries of small molecules are being explored extensively for the identification of binders in early drug-discovery efforts. Combinatorial syntheses of such libraries require water- and DNA-compatible reactions, and the paucity of these reactions currently limit the chemical features of resulting barcoded products. The present work introduces strain-promoted cycloadditions of cyclic allenes under mild conditions to DNA-encoded library synthesis. Owing to distinct cycloaddition modes of these reactive intermediates with activated olefins, 1,3-dipoles, and dienes, the process generates diverse molecular architectures from a single precursor. The resulting DNA-barcoded compounds exhibit unprecedented ring and topographic features, related to elements found to be powerful in phenotypic screening.

Construction of Thiazole-Fused Dihydropyrans via Formal [4 + 2] Cycloaddition Reaction on DNA

An efficient and facile formal [4 + 2] cycloaddition reaction was developed to synthesize diverse thiazole-fused dihydropyrans (TFDP) on DNA. Mild reaction conditions, broad substrate scope, and compatibility with subsequent enzymatic ligation demonstrated the utility of this methodology in DNA-encoded library synthesis.

Photocatalytic [2 + 2] Cycloaddition in DNA-Encoded Chemistry

The on-DNA synthesis of highly substituted cyclobutanes was achieved through a photocatalytic [2 + 2] cycloaddition reaction in aqueous solution. Readily available DNA-tagged styrene derivatives were reacted with structurally diverse cinnamates in the presence of an iridium-based photocatalyst, Ir(ppy)₂(dtbbpy)PF₆, to forge two new C(sp³)-C(sp³) bonds. This transformation was demonstrated to have excellent functional group tolerance and allowed for the facile installation of a variety of heteroaromatic substituents on a densely functionalized cyclobutane scaffold.

An Amphiphilic Polymer-Supported Strategy Enables Chemical Transformations under Anhydrous Conditions for DNA-Encoded Library Synthesis

The use of DNA-encoded libraries has emerged as a powerful hit generation technology. Combining the power of combinatorial chemistry to enumerate large compound collections with the efficiency of affinity selection in pools, the methodology makes it possible to interrogate vast chemical space against biological targets of pharmaceutical relevance. Thus, the chemical transformations employed for the synthesis of encoded libraries play a crucial role in the identification of diverse and drug-like starting points. Currently established transformations have mostly been limited to water-compatible reactions to accommodate the growing oligonucleotide tag. Herein, we describe the development of a practical catch-and-release methodology utilizing a cationic, amphiphilic PEG-based polymer to perform chemical transformations on immobilized DNA conjugates under anhydrous conditions. We demonstrate the usefulness of our APTAC (amphiphilic polymer-facilitated transformations under anhydrous conditions) approach by performing several challenging transformations on DNA-conjugated small molecules in pure organic solvents: the addition of a carbanion equivalent to a DNA-conjugated ketone in tetrahydrofuran, the synthesis of saturated heterocycles using the tin (Sn) amine protocol (SnAP) in dichloromethane, and the dual-catalytic (Ir/Ni) metallaphotoredox decarboxylative cross-coupling of carboxylic acids to DNA-conjugated aryl halides in DMSO. In addition, we demonstrate the feasibility of the latter in multititer-plate format.

C-N Coupling of DNA-Conjugated (Hetero)aryl Bromides and Chlorides for DNA-Encoded Chemical Library Synthesis

DNA-encoded chemical library (DECL) screens are a rapid and economical tool to identify chemical starting points for drug discovery. As a robust transformation for drug discovery, palladium-catalyzed C–N coupling is a valuable synthetic method for the construction of DECL chemical matter; however, currently disclosed methods have only been demonstrated on DNA-attached (hetero)aromatic iodide and bromide electrophiles. We developed conditions utilizing an N-heterocyclic carbene–palladium catalyst that extends this reaction to the coupling of DNA-conjugated (hetero)aromatic chlorides with (hetero)aromatic and select aliphatic amine nucleophiles. In addition, we evaluated steric and electronic effects within this catalyst series, carried out a large substrate scope study on two representative (hetero)aryl bromides, and applied this newly developed method within the construction of a 63 million-membered DECL.

DNA-Encoded Library Screening as Core Platform Technology in Drug Discovery: Its Synthetic Method Development and Applications in DEL Synthesis

DNA-encoded library technology (DELT) was introduced to our medicinal chemistry society more than 20 years ago. The application of DELT in the development of clinical candidates has been actively reported in the literature recently. A few representative examples include RIP1K inhibitors for inflammatory diseases and sEH inhibitors for endothelial dysfunction or abnormal tissue repair, among many others. Here, the authors would like to recall the recent developments in on-DNA synthetic methodologies for DEL construction and to analyze recent examples in the literature of DELT-based drug development efforts pursued in both the academic and industrial sectors. With this perspective, we hope to provide a useful summary of recent DELT-based drug discovery research and to discuss the future scope of DELT in medicinal chemistry.

Homogeneous and Functional Group Tolerant Ring-Closing Metathesis for DNA-Encoded Chemical Libraries

Reaction heterogeneity, poor pH control, and catalyst decomposition in the ring-closing metathesis (RCM) of DNA-chemical conjugates lead to poor yields of the cyclized products. Herein we address these issues with a RCM reaction system that includes a novel aqueous solvent combination to enable reaction homogeneity, an acidic buffer system which masks traditionally problematic functional groups, and a decomposition-resistant catalyst which maximizes conversion to the cyclized product. Additionally, we provide a systematic study of the substrate scope of the on-DNA RCM reaction, a demonstration of its applicability to a single-substrate DNA-encoded chemical library that includes sequencing analysis, and the first successful stapling of an unprotected on-DNA [i, i+4] peptide.

DNA-Encoded Libraries: Aryl Fluorosulfonates as Versatile Electrophiles Enabling Facile On-DNA Suzuki, Sonogashira, and Buchwald Reactions

Using (hetero)aryl fluorosulfonates as versatile electrophiles, facile on-DNA cross-coupling reactions of Suzuki, Sonogashira, and Buchwald are reported here. Notably, all of these reactions show excellent functional group tolerance, mild reaction conditions (relative low temperature and open to air), rich heterocyclic coupling partners, and more importantly, DNA-compatibility. Thus, these new reactions based on efficient formation of C(sp2)-C(sp2), C(sp2)-C(sp), and C(sp2)-N bonds are highly amenable to synthesis of DNA-encoded libraries with great molecular diversity.

Isocyanide Multicomponent Reactions on Solid-Phase-Coupled DNA Oligonucleotides for Encoded Library Synthesis

Isocyanide multicomponent reactions play a prominent role in drug discovery. This chemistry has hardly been investigated for compatibility with DNA-encoded combinatorial synthesis. The Ugi, Ugi-azide, and Groebke-Blackburn-Bienaymé reactions are well-tolerated by DNA on the solid phase and show a broad scope. However, an oxadiazole-forming variant of the Ugi reaction caused DNA depurination, requiring a more stable hexathymidine DNA for encoded library synthesis. Cheminformatic analysis revealed that isocyanide multicomponent-reaction-based encoded libraries cover a diverse chemical space.

On-DNA Decarboxylative Arylation: Merging Photoredox with Nickel Catalysis in Water

A new catalytic manifold that merges photoredox with nickel catalysis in aqueous solution is presented. Specifically, the combination of a highly active, yet air-stable, nickel precatalyst with a new electron-deficient pyridyl carboxamidine ligand was key to the development of a water-compatible nickel catalysis platform, which is a crucial requirement for the preparation of DNA-encoded libraries (DELs). Together with an iridium-based photocatalyst and a powerful light source, this dual catalysis approach enabled the efficient decarboxylative arylation of α-amino acids with DNA-tagged aryl halides. This C(sp²)-C(sp³) coupling tolerates a wide variety of functional groups on both the amino acid and the aryl halide substrates. Due to the mild and DNA-compatible reaction conditions, the presented transformation holds great potential for the construction of DELs. This was further evidenced by showing that well plate-compatible LED arrays can serve as competent light sources to facilitate parallel synthesis. Lastly, we demonstrate that this procedure can serve as a blueprint toward the adaptation of other established nickel metallaphotoredox transformations to the idiosyncratic requirements of a DEL.

Palladium-Catalyzed Hydroxycarbonylation of (Hetero)aryl Halides for DNA-Encoded Chemical Library Synthesis

A strategy for DNA-compatible, palladium-catalyzed hydroxycarbonylation of (hetero)aryl halides on DNA–chemical conjugates has been developed. This method generally provided the corresponding carboxylic acids in moderate to very good conversions for (hetero)aryl iodides and bromides, and in poor to moderate conversions for (hetero)aryl chlorides. These conditions were further validated by application within a DNA-encoded chemical library synthesis and subsequent discovery of enriched features from the library in selection experiments against two protein targets.

Synthesis of DNA-coupled isoquinolones and pyrrolidines by solid phase ytterbium- and silver-mediated imine chemistry

DNA-encoded libraries of chemically synthesized compounds are an important small molecule screening technology. The synthesis of encoded compounds in solution is currently restricted to a few DNA-compatible and water-tolerant reactions. Encoded compound synthesis of short DNA-barcodes covalently connected to solid supports benefits from a broad range of choices of organic solvents. Here, we show that this encoded chemistry approach allows for the synthesis of DNA-coupled isoquinolones by an Yb(iii)-mediated Castagnoli-Cushman reaction under anhydrous reaction conditions and for the synthesis of highly substituted pyrrolidines by Ag(i)-mediated 1,3-dipolar azomethine ylide cycloaddition. An encoding scheme for these DNA-barcoded compounds based on a DNA hairpin is demonstrated.

DNA Barcoding a Complete Matrix of Stereoisomeric Small Molecules

It is challenging to incorporate stereochemical diversity and topographic complexity into DNA-encoded libraries (DELs) because DEL syntheses cannot fully exploit the capabilities of modern synthetic organic chemistry. Here, we describe the design, construction, and validation of DOS-DEL-1, a library of 107 616 DNA-barcoded chiral 2,3-disubsituted azetidines and pyrrolidines. We used stereospecific C-H arylation chemistry to furnish complex scaffolds primed for DEL synthesis, and we developed an improved on-DNA Suzuki reaction to maximize library quality. We then studied both the structural diversity of the library and the physicochemical properties of individual compounds using Tanimoto multifusion similarity analysis, among other techniques. These analyses revealed not only that most DOS-DEL-1 members have "drug-like" properties, but also that the library more closely resembles compound collections derived from diversity synthesis than those from other sources (e.g., commercial vendors). Finally, we performed validation screens against horseradish peroxidase and carbonic anhydrase IX, and we developed a novel, Poisson-based statistical framework to analyze the results. A set of assay positives were successfully translated into potent carbonic anhydrase inhibitors (IC₅₀ = 20.1-68.7 nM), which confirmed the success of the synthesis and screening procedures. These results establish a strategy to synthesize DELs with scaffold-based stereochemical diversity and complexity that does not require the development of novel DNA-compatible chemistry.

Encoded Library Technologies as Integrated Lead Finding Platforms for Drug Discovery

The scope of targets investigated in pharmaceutical research is continuously moving into uncharted territory. Consequently, finding suitable chemical matter with current compound collections is proving increasingly difficult. Encoded library technologies enable the rapid exploration of large chemical space for the identification of ligands for such targets. These binders facilitate drug discovery projects both as tools for target validation, structural elucidation and assay development as well as starting points for medicinal chemistry. Novartis internalized two complementing encoded library platforms to accelerate the initiation of its drug discovery programs. For the identification of low-molecular weight ligands, we apply DNA-encoded libraries. In addition, encoded peptide libraries are employed to identify cyclic peptides. This review discusses how we apply these two platforms in our research and why we consider it beneficial to run both pipelines in-house.

A Mild, DNA-Compatible Nitro Reduction Using B2(OH)4

A hypodiboric acid system for the reduction of nitro groups on DNA–chemical conjugates has been developed. This transformation provided good to excellent yields of the reduced amine product for a variety of functionalized aromatic, heterocyclic, and aliphatic nitro compounds. DNA tolerance to reaction conditions, extension to decigram scale reductions, successful use in a DNA-encoded chemical library synthesis, and subsequent target selection are also described.

DNA-Compatible [3 + 2] Nitrone-Olefin Cycloaddition Suitable for DEL Syntheses

The limited scope of DNA-compatible chemistry restricts the types of chemical features that can be incorporated into DNA-encoded libraries (DELs). Here, a method to synthesize DNA-conjugated polycyclic isoxazolidines via a [3 + 2] nitrone-olefin cycloaddition is described. The reaction is compatible with many olefin-containing substrates and diverse N-alkylhydroxylamines. The ability to perform subsequent DNA ligation and PCR amplification was also confirmed. This methodology facilitates the synthesis of DELs containing topographically complex compounds with underexplored chemical features.

Open-Air Alkylation Reactions in Photoredox-Catalyzed DNA-Encoded Library Synthesis

DNA-encoded library (DEL) technology is a powerful tool commonly used by the pharmaceutical industry for the identification of compounds with affinity to biomolecular targets. Success in this endeavor lies in sampling diverse chemical libraries. However, current DELs tend to be deficient in C(sp³) carbon counts. We report unique solutions to the challenge of increasing both the chemical diversity of these libraries and their C(sp³) carbon counts by merging Ni/photoredox dual catalytic C(sp²)-C(sp³) cross-coupling as well as photoredox-catalyzed radical/polar crossover alkylation protocols with DELs. The successful integration of multiple classes of radical sources enables the rapid incorporation of a diverse set of alkyl fragments.

Mild and Efficient Palladium-Mediated C-N Cross-Coupling Reaction between DNA-Conjugated Aryl Bromides and Aromatic Amines

DNA-encoded library technology (ELT) has emerged in the pharmaceutical industry as a powerful tool for hit and lead generation. Over the last 10 years, a number of DNA-compatible chemical reactions have been published and used to synthesize libraries. Among the most commonly used reactions in medicinal chemistry is the C-N bond formation, and its application to DNA-encoded library technology affords an alternative approach to identify high-affinity binders for biologically relevant protein targets. Herein we report a newly developed Pd-promoted C-N cross coupling reaction between DNA-conjugated aryl bromides and a wide scope of arylamines in good to excellent yields. The mild reaction conditions should facilitate the synthesis of novel DNA-encoded combinatorial libraries.

Inverse-Electron-Demand Diels-Alder Reactions for the Synthesis of Pyridazines on DNA

The synthesis of pyridazines on DNA has been developed on the basis of inverse-electron-demand Diels-Alder (IEDDA) reactions of 1,2,4,5-tetrazines. The broad substrate scope is explored. Functionalized pyridazine products are selected for subsequent DNA-compatible Suzuki-Miyaura coupling, acylation, and S_NAr substitution reactions, demonstrating the feasibility and versatility of IEDDA reactions for DNA-encoded library synthesis.