Comprehensive Survey of Chemical Libraries for Drug Discovery and Chemical Biology: 2007

Rapid construction of γ-lactam containing 3,3-disubstituted oxindoles via a silver-catalyzed cascade radical bicyclization reaction

An efficient cascade bicyclization strategy for the construction of γ-lactam containing 3,3-disubstituted oxindole derivatives is described, which enables the sequential assembly of both unactivated and activated double bonds in one pot.

Synthesis of Novel 2-(Pyridin-2-yl) Pyrimidine Derivatives and Study of Their Anti-Fibrosis Activity

A pyrimidine moiety exhibiting a wide range of pharmacological activities has been employed in the design of privileged structures in medicinal chemistry. To prepare libraries of novel heterocyclic compounds with potential biological activities, a series of novel 2-(pyridin-2-yl) pyrimidine derivatives were designed, synthesized and their biological activities were evaluated against immortalized rat hepatic stellate cells (HSC-T6). Fourteen compounds were found to present better anti-fibrotic activities than Pirfenidone and Bipy55'DC. Among them, compounds ethyl 6-(5-(p-tolylcarbamoyl)pyrimidin-2-yl)nicotinate (12m) and ethyl 6-(5-((3,4-difluorophenyl)carbamoyl)pyrimidin-2-yl)nicotinate (12q) show the best activities with IC₅₀ values of 45.69 μM and 45.81 μM, respectively. Furthermore, the study of anti-fibrosis activity was evaluated by Picro-Sirius red staining, hydroxyproline assay and ELISA detection of Collagen type I alpha 1 (COL1A1) protein expression. Our study showed that compounds 12m and 12q effectively inhibited the expression of collagen, and the content of hydroxyproline in cell culture medium in vitro, indicating that compounds 12m and 12q might be developed the novel anti-fibrotic drugs.

Synthesis of Tris-Heterocycles via a Cascade IMCR/Aza Diels-Alder + CuAAC Strategy

6-Triazolylmethyl-pyrrolo[3,4-b]pyridin-5-one tris-heterocycles were synthesized in 43-57% overall yields. The two-stage synthesis involved a cascade process (Ugi-3CR/aza Diels-Alder/N-acylation/aromatization) followed by a copper-assisted alkyne-azide [3+2] cycloaddition (CuAAC). This efficient and convergent strategy proceeded via complex terminal alkynes functionalized with a fused bis-heterocycle at the α-position. The final products are ideal candidates for SAR studies as they possess two privileged scaffolds in medicinal chemistry: 4-substituted or 1,4-substituted 1H-1,2,3-triazoles and pyrrolo[3,4-b]pyridin-5-ones.

Regioselective Synthesis of Pyranone-Fused Indazoles via Reductive Cyclization and Alkyne Insertion

A novel and efficient method for the one-pot synthesis of 2 H-indazole from readily available building blocks is reported. The reaction of 2-nitrobenzylamines with zinc and ammonium formate underwent partial reduction to nitroso-benzylamine followed by an intramolecular cyclization to afford 2 H-indazole via N-N bond formation. The carboxylic acid moiety of indazole was proceeded to regioselective alkyne insertion under ruthenium catalysis to form pyranone-fused indazoles. The regioselectivity is influenced by the weak coordination of indazole ring nitrogen to the metal center.

New tricks of well-known aminoazoles in isocyanide-based multicomponent reactions and antibacterial activity of the compounds synthesized

The well-known aminoazoles, 3-amino-5-methylisoxazole and 5-amino-N-aryl-1H-pyrazole-4-carboxamides, were studied as an amine component in Ugi and Groebke-Blackburn-Bienaymé multicomponent reactions. The first example of an application of aminoazoles in an Ugi four-component reaction was discovered and novel features of a Groebke-Blackburn-Bienaymé cyclocondensation are established and discussed. The heterocycles obtained were evaluated for their antibacterial activity and several of them demonstrated a weak antimicrobial effect, but for most of the compounds a 30-50% increase in biomass of Gram-positive strains (mainly B. subtilis) compared to control was observed.

Novel skeleton compound Allomyrinanoid A and two purine alkaloids from the adult of Allomyrina dichotoma L

Three new compounds were isolated from the adult insect of Allomyrina dichotoma L. for the first time. A new skeleton compound is named as Allomyrinanoid A (1) originated from the familiar norbornane derivatives and two new compounds of purine alkaloid are named as adenine-9-methylaldehyde oxime B (2) and 6-N-methyleneimine-adenine-9-methylaldehyde oxime B (3). The compounds (2) and (3) are the tautomers of imine-enamine and creatively separated form the solvent using column chromatography method. The structures of all isolated compounds were established by spectroscopic methods including analyses of their 1D, 2D NMR and HRESI-MS data, and confirmed by comparison of the literature data. These new components displayed antibacterial activities against both Gram-positive and Gram-negative strain.

Diversity oriented synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approach: a critical review

Because of the wide ranging bioactivities associated with the benzimidazole nucleus, this review highlights the advances made in the synthesis of benzimidazole-based biheterocyclic molecules by combinatorial approaches.

Solid-supported cross-metathesis and a formal alkane metathesis for the generation of biologically relevant molecules

Solid-phase synthetic strategies toward the generation of libraries of biologically relevant molecules were developed using olefin cross-metathesis as a key step. It is remarkably the formal alkane metathesis based on a one-pot, microwave-assisted, ruthenium-catalyzed cross-metathesis and reduction to obtain Csp3-Csp3 linkages.

Two Efficient One-Pot Approaches for Regioselective Synthesis of New 3-Arylpyridazino[4,3-c]quinolin-5(6H)-ones

Two efficient regioselective approaches for the one-pot synthesis of 3-arylpyridazino[4,3-c]quinolin-5(6H)-one derivatives are reported, by the three-component reaction of arylglyoxal monohydrates, quinoline-2,4-diol, and hydrazinium dihydrochloride or hydrazine hydrate in ethanol and pyridine. In ethanol, the reactions were catalyzed by 1,4-diazobicyclo[2,2,2]octane. The features of both procedures are high regioselectivity, mild reaction conditions, good to high yields, and operational simplicity.

Ugi-based approaches to quinoxaline libraries

An expedient and concise Ugi-based unified approach for the rapid assembly of quinoxaline frameworks has been developed. This convergent and versatile method uses readily available commercial reagents, does not require advanced intermediates, and exhibits excellent bond-forming efficiency, thus exemplifying the operationally simple synthesis of quinoxaline libraries.

Three-component coupling approach for the synthesis of diverse heterocycles utilizing reactive nitrilium trapping

The formation of an unexpected heterocyclic scaffold, a benzoxazole, in a three-component reaction between a ketone, isocyanide, and 2-aminophenol was encountered. This reaction involved a benzo[b][1,4]oxazine intermediate resulting from intramolecular attack of the aminophenol hydroxyl group on the nitrilium ion. Unlike previous literature examples, the trapped nitrilium benzo[b][1,4]oxazine could readily be subjected to ring opening with bis-nucleophiles. The reaction scope includes simple linear as well as complex cyclic ketones and substituted 2-aminophenols. A representative benzoxazole product could be further diversified to yield drug-like compounds.

Recent progress on fluorous synthesis of biologically interesting compounds

This article highlights research papers published in 2011 and 2012 on fluorous linker-assisted synthesis of biologically interesting small molecules and biomolecules.

Copper-catalyzed electrophilic amination of organolithiums mediated by recoverable siloxane transfer agents

The development and validation of copper-catalyzed, electrophilic amination of aryl and heteroaryl organolithiums with N,N-dialkyl-O-benzoylhydroxylamines have been achieved exploiting recoverable siloxane transfer agents. Given the ready availability of organolithium compounds, the mild reaction conditions, the ease of product purification, and the ready recovery of the siloxane transfer agents, this transformation comprises a useful tactic to access diverse aryl and heteroaryl amines.

Multicomponent solvent-free synthesis of benzimidazolyl imidazo[1,2-a]-pyridine under microwave irradiation

A novel one-pot, three-component reaction employing variously substituted benzimidazole-linked amino pyridines, aldehydes, and isonitriles catalyzed by scandium(III) triflate under solvent-free conditions were accomplished. This new synthetic methodology facilitates the rapid generation of intricate molecular frameworks in three-dimensional fashion leading to benzimidazole-imidazo[1,2-a] pyridines. This approach is envisioned as an environmentally benign process and a simple operation to the biological interesting compounds. The present synthetic sequence permits the introduction of three points of structural diversity to expand chemical space with high purity and excellent yields.

Diversity oriented synthesis of a vinblastine-templated library of 7-aryl-octahydroazonino[5,4-b]indoles via a three-component reaction

A vinblastine-templated library of 7-aryl-octahydroazonino[5,4-b]indoles was prepared by a three-component reaction from indolizino[8,7-b]indoles, chloroformates, and activated arenes via a chloroformate mediated fragmentation of the indolizinoindole nucleus followed by insertion of an activated arene. In addition to N3-carbamoyl-7-aryl-octahydroazonino[5,4-b]indoles prepared in one step, a wide range of N3-substituted substrates were synthesized in one pot via the derivatization of a versatile N3-H-azonino[5,4-b]indole intermediate generated in situ by application of the same strategy. A subset of 308 compounds out of a virtual library of 3216, representing 13 different chemotypes, was prepared by high throughput solution-phase synthesis and subsequently purified by mass-triggered high performance liquid chromatography (HPLC). A total of 188 compounds with a minimum purity of 80% by UV214 nm and 85% by evaporative light scattering detection (ELSD) was isolated for primary screening.

Parallel chemistry in the 21st century

The tool chest of techniques, methodologies, and equipment for conducting parallel chemistry is larger than ever before. Improvements in the laboratory and developments in computational chemistry have enabled compound library design at the desks of medicinal chemists. This unit includes a brief background in combinatorial/parallel synthesis chemistry, along with a discussion of evolving technologies for both solid- and solution-phase chemistry. In addition, there are discussions on designing compound libraries, acquisition/procurement of compounds and/or reagents, the chemistry and equipment used for chemical production, purification, sample handling, and data analysis.

Diversity-oriented synthesis of 1-substituted 4-aryl-6-oxo-1,6-dihydropyridine-3-carboxamides

A simple five-step diversity-oriented synthesis of 1-substituted 4-aryl-6-oxo-1,6-dihydropyridine-3-carboxamides was developed. Treatment of dimethyl 2-((dimethylamino)methylidene)-3-oxopentanedioate with twenty primary amines gave 1-substituted methyl 4-hydroxy-6-oxo-1,6-dihydropyridine-3-carboxylates. Transformation into the corresponding 4-tosyloxy and 4-chloro derivatives, followed by Suzuki-Miyaura arylations gave a series of eleven N-substituted methyl 4-aryl-6-oxo-1,6-dihydropyridine-3-carboxylates. Combinatorial screening was employed to establish suitable reaction conditions for Suzuki-Miyaura arylation of N-alkylpyridones. Hydrolysis of the esters followed by parallel solution-phase amidation of the corresponding carboxylic acids with primary and secondary amines furnished a library of seventeen final products.

Iodine-catalyzed synthesis of 5-arylanthra[2,1-c][2,7]naphthyridine derivatives via three-component reaction

A series of ethyl 5-aryl-1,2-dihydroanthra[2,1-c][2,7]naphthyridine-3(4H)-carboxylate derivatives was prepared by a three-component reaction of aromatic aldehyde, anthracen-2-amine and ethyl 4-oxopiperidine-1-carboxylate using iodine as catalyst. This iodine-catalyzed procedure has the advantages of mild reaction conditions, good yields, operational simplicity and metal-free catalyst.

Solid-phase parallel synthesis of drug-like artificial 2H-benzopyran libraries

This review covers the construction of drug-like 2H-benzopyrans and related libraries using solid-phase parallel synthesis. In this context, the preparation of substituted benzopyrans such as mono-, di- and trisubstituted benzopyran derivatives and additional ring-fused benzopyrans such as benzopyranoisoxazoles, benzopyranopyrazoles, six-membered ring-fused benzopyrans, and polycyclic benzopyrans are highlighted.

Parallel synthesis of 2-substituted 6-(5-oxo-1-phenylpyrrolidin-3-yl)pyrimidine-5-carboxamides

A library of 24 6-(5-oxo-1-phenylpyrrolidin-3-yl)pyrimidine-5-carboxamides 10{1,2; 1-12} was prepared by a parallel solution-phase approach. The synthesis comprises a five-step transformation of itaconic acid (11) into 1-methyl and 1-phenyl substituted 6-(5-oxo-1-phenylpyrrolidin-3-yl)pyrimidine-5-carboxylic acids 17{1,2} followed by parallel amidation of 17{1,2} with a series of 12 aliphatic amines 18{1-12} to afford the corresponding carboxamides 10 in good overall yields and in 80-100% purity.

Facile (triazolyl)methylation of MACOS-derived benzofused sultams utilizing ROMP-derived OTP reagents

A combination of MACOS scale-out and ROMP-derived oligomeric triazole phosphates (OTP(n)) have been successfully utilized for the preparation of a 106-member library of triazole containing benzothiaoxazepine-1,1-dioxides. This report demonstrates the utilization of a suite of soluble OTP(n) reagents for facile (triazolyl)methylation of 10 MACOS-derived sultam scaffolds in purification-free process for parallel synthesis of small molecule collections for HTS.

Synthesis of a unique isoindoline/tetrahydroisoquinoline-based tricyclic sultam library utilizing a Heck-aza-Michael strategy

The synthesis of a unique isoindoline- and tetrahydroisoquinoline (THIQ)-containing tricyclic sultam library, utilizing a Heck-aza-Michael (HaM) strategy is reported. Both isoindoline and THIQ rings are installed through a Heck reaction on a vinylsulfonamide, followed by one-pot deprotection and intramolecular aza-Michael reaction. Subsequent cyclization with either paraformaldehyde condensation or 1,1'-carbonyldiimidazole coupling generates a variety of tricyclic sultams. Overall, a 160-member library of these sultams, together with their isoindolines/THIQ and secondary sulfonamides precursors, were constructed using this strategy.

Combinatorial and high-throughput screening of materials libraries: review of state of the art

Rational materials design based on prior knowledge is attractive because it promises to avoid time-consuming synthesis and testing of numerous materials candidates. However with the increase of complexity of materials, the scientific ability for the rational materials design becomes progressively limited. As a result of this complexity, combinatorial and high-throughput (CHT) experimentation in materials science has been recognized as a new scientific approach to generate new knowledge. This review demonstrates the broad applicability of CHT experimentation technologies in discovery and optimization of new materials. We discuss general principles of CHT materials screening, followed by the detailed discussion of high-throughput materials characterization approaches, advances in data analysis/mining, and new materials developments facilitated by CHT experimentation. We critically analyze results of materials development in the areas most impacted by the CHT approaches, such as catalysis, electronic and functional materials, polymer-based industrial coatings, sensing materials, and biomaterials.

Synthesis of amino-benzothiaoxazepine-1,1-dioxides utilizing a microwave-assisted, S(N)Ar protocol

The development of a microwave-assisted, intermolecular S(N)Ar protocol for the synthesis of a 126-member benzothiaoxazepine-1,1-dioxide library is reported. Diversification of 12 benzothiaoxazepine-1,1-dioxides was achieved in rapid fashion utilizing a variety of 2° amines and amino alcohols to generate an 80-member library. A second 48-member library was subsequently generated via a two-step alkylation, intermolecular S(N)Ar diversification protocol.

High Throughput Chemistry in Drug Discovery

This chapter outlines the evolution of high throughput chemistry from its origins in the genome revolution of the early 1990's to its current practice as an integral tool in drug discovery, via the concept of the large “universal library” to the practice of small targeted arrays for structure–activity relationship generation. The technologies developed as part of this evolution are also outlined including early ACT peptide synthesisers and other automated and non-automated devices for both solid-supported and solution-based approaches. Finally, the chapter outlines several case studies of the application of high throughput synthesis to drug discovery.

Triazole-containing isothiazolidine 1,1-dioxide library synthesis: one-pot, multi-component protocols for small molecular probe discovery

The construction of two libraries of triazole-containing isothiazolidine 1,1-dioxides is reported utilizing either a one-pot click/aza-Michael or click/OACC esterification protocol. One core dihydroisothiazole 1,1-dioxide scaffold was prepared rapidly on multigram scale via ring-closing metathesis (RCM) and was subjected to a one-pot multicomponent click/aza-Michael protocol with an array of amines and azides for the generation of a 180-member triazole-containing isothiazolidine 1,1-dioxide library. Alternatively, three daughter scaffolds were generated via the aza-Michael of three amino alcohols, followed by a one-pot, multicomponent click/esterification protocol utilizing a ring-opening metathesis polymerization (ROMP)-derived coupling reagent, oligomeric alkyl carbodiimide (OACC) to generate a 41-member library of triazole-containing isothiazole 1,1-dioxides.

Polymer supported synthesis of novel benzoxazole linked benzimidazoles under microwave conditions: in vitro evaluation of VEGFR-3 kinase inhibition activity

An efficient soluble polymer-supported method has been developed for the parallel synthesis of substituted benzimidazole linked benzoxazoles using focused microwave irradiation. The key step involves the amidation of 4-hydroxy-3-nitrobenzoic acid with polymer-immobilized o-phenylenediamine. Application of mild acidic conditions promoted the ring closure to furnish the benzimidazole ring. After hydrogenation of the nitro-group to amine, the resulted polymer conjugates underwent efficient ring closure with various alkyl, aryl and heteroaryl isothiocyanates to generate the polymer-bound benzimidazolyl benzoxazoles. The polymer-bound compounds were finally cleaved from the support to furnish benzimidazole linked benzoxazole derivatives. The efficacy of the resultant angular bis-heterocyclic library was studied against vascular endothelial growth factor receptor (VEGFR-3). The preliminary screening of these novel compounds exhibits moderate to high inhibition (IC(50) = 0.56-1.42 μM). This protocol provides an easy access to novel angular bis-heterocycles which have potential for the discovery of novel leads for targeted cancer therapeutics.

Total synthesis of (+/-)-marinopyrrole A and its library as potential antibiotic and anticancer agents

The first total synthesis of marine natural product, (+/-)-marinopyrrole A, has been accomplished via a nine-step synthesis in an overall yield of 30%. A small focused library based on marinopyrrole has been designed and synthesized. The scope of chemistry was investigated, and a robust chemistry suitable for library synthesis has been developed in the current study. The method that we have developed has made it possible to generate diverse analogues based on structurally novel marinopyrroles for study of potential antibiotic and anticancer activities.

Divergent solution-phase synthesis of diarylpyrimidine libraries as selective A3 adenosine receptor antagonists

A practical and divergent solution-phase synthetic strategy has been optimized to prepare a highly diverse library of 2,4-diaryl- and 2,6-diarylpyrimidines. Structural elaboration of the starting heterocyclic scaffolds was accomplished by exploiting the potential for diversity offered by the Suzuki-Miyaura cross-coupling reaction. These studies enabled the identification of structurally simple, highly potent, and selective A(3) adenosine receptor antagonists.