Solution-phase Parallel Synthesis Research Articles

Design, Synthesis, and Anti-Cancer Activity Evaluation of a 3-methyleneisoindolin- 1-One Library.

Isoindolin-1-ones are medicinally privileged heterocyclic compounds. Due to the interesting biological activities exhibited by these compounds, several synthetic and medicinal research groups have developed numerous synthetic approaches for these compounds. We have also previously reported two efficient approaches for the synthesis of the isoindolin-1-ones through iodoaminocyclization of alkynyl amides using n-BuLi and phosphazene superbases. This study aimed to construct a medium-size library of multi-substituted 3- methyleneisoindolin-1-ones and study its biological profile, specifically anti-cancer activity. Solution phase parallel synthesis was performed for the synthesis of the 3- methyleneisoindolin-1-ones library through n-BuLi-mediated iodoaminocyclization of 2(1- Alkynyl)benzamides. The iodocyclized products were further derivatized through palladiumcatalyzed Sonogashira and Suzuki Miyaura couplings and N-alkylation reactions. In silico evaluation of the physicochemical and ADMET properties was performed to examine the drug-likeness of the library compounds. Selected isoindolin-1-one analogues were evaluated for in vitro antiproliferative activity in various human cancer cell lines (MCF-7, A-549, and U-373 MG). A library of 46 multisubstituted 3-methyleneisoindolin-1-ones has been synthesized. The iodo-isoindolin-1-ones were synthesized in 66-76% yields through n-BuLi-mediated iodoaminocyclization of 2(1-Alkynyl)benzamides. Further diversification afforded the diverse library members in yields of 40-96%. Two of the library compounds exhibited GI50 values of < 10 μM in the human breast cancer cell line (MCF-7). Isoindolin-1-one library was constructed through electrophilic cyclization. The diversification was successfully performed through various C-C and C-N bond formation reactions. The anti-proliferative activity of the library members appears to be arising from the interaction of the compounds with the protein kinase drug targets.

Enabling Metallophotoredox Catalysis in Parallel Solution-Phase Synthesis Using Disintegrating Reagent Tablets.

Compressed tablets containing a mixture of a photocatalyst, a nickel catalyst, an inorganic base, and an inert excipient are employed as a fast, safe, and user-friendly chemical delivery system for two different metallophotoredox-catalyzed reactions. This delivery method simplifies the preparation of compound libraries using photoredox chemistry in a parallel setting. The reagent tablets were successfully applied to late-stage functionalization of drug-like intermediates. These tablets can be prepared with various reagents and catalysts in different sizes and be stored on the bench thanks to blister packaging.

Rapid Synthesis of a Natural Product-Inspired Uridine Containing Library.

The preparation of natural product-inspired nucleoside analogs using solution-phase parallel synthesis is described. The key intermediates containing alkyne and N-protected amino moieties were developed to allow for further skeleton and substituent diversity using click chemistry and urea or amide bond formation. Rapid purification was accomplished using solid-phase extraction. The obtained library comprised 80 molecules incorporating two diversity positions and one chiral center, each of which was efficiently prepared in good purity and acceptable overall yield. A bacterial morphology study was also performed.

Parallel Solution Phase Synthesis and Preliminary Biological Activity of a 5'-Substituted Cytidine Analog Library.

A 109-membered library of 5'-substituted cytidine analogs was synthesized, via funding through the NIH Roadmap Initiative and the Pilot Scale Library (PSL) Program. Reaction core compounds contained -NH2 (2) and -COOH (44 and 93) groups that were coupled to a diversity of reactants in a parallel, solution phase format to produce the target library. The assorted reactants included -NH2, -CHO, -SO2Cl, and -COOH functional groups, and condensation with the intermediate core materials 2 and 44 followed by acidic hydrolysis produced 3-91 in good yields and high purity. Linkage of the amino terminus of d-phenylalanine methyl ester to the free 5'-COOH of 44 and NaOH treatment led to core library -COOH precursor 93. In a libraries from libraries approach, compound 93 served as the vital building block for our unique library of dipeptidyl cytidine analogs 94-114 through amide coupling of the -COOH group with numerous commercial amines followed by acidic deprotection. Initial screening of the complete final library through the MLPCN program revealed a modest number of hits over diverse biological processes. These hits might be considered as starting points for hit-to-lead optimization and development studies.

Solution-phase microwave assisted parallel synthesis, biological evaluation and in silico docking studies of 2-chlorobenzoyl thioureas derivatives

An efficient and facile microwave-assisted solution phase parallel synthesis for a 38-member library of N-aroyl-N′-aryl thioureas was accomplished successfully. These analogues (1–38) were synthesized under identical set of conditions. It has been observed that the reaction time was drastically reduced from 8 to 12 h for conventional methods to only 10–15 mins. Products obtained were more than 98% pure, as characterized by elemental analysis along with FT-IR and 1H, 13C NMR. The solid-phase structural analysis was accomplished by single crystal XRD analysis. The urease inhibitory potential of synthetic compounds was tested and compounds were found to inhibit urease in moderate to significant manner. Compound 17 was the most potent inhibitor of urease having an IC50 value of 0.17 ± 0.1 μM. To check the cytotoxic profile of the derivatives, lungs cancer cell lines were used. Cytotoxicity analysis revealed remarkable toxicity of the compounds against tested lungs carcinoma and compounds showed variation in inhibition activity due to the substituents attached. The molecular docking studies were carried out to identify the possible binding modes of potent inhibitors in the active site of enzyme. The results suggested that the compounds can be further investigated and used against different cancers.

The design, synthesis, and anti-inflammatory evaluation of a drug-like library based on the natural product valerenic acid

The plant natural product, valerenic acid (1) was chosen as a desirable scaffold for the generation of a novel screening library due to its drug-like physicochemical parameters (such as LogP, hydrogen bond donor/acceptor counts, and molecular weight). An 11-membered amide library (2–12) was subsequently generated using parallel solution-phase synthesis and Ghosez’s reagent. The chemical structures of all semi-synthetic analogues (2–12) were elucidated following analysis of the NMR, MS, UV and IR data. The structures of compounds 8 and 11 were also confirmed by X-ray crystallographic analysis. All library members were evaluated for their ability to inhibit the release of IL-8 and TNF-α. Six analogues showed moderate activity in the IL-8 assay with IC50 values of 2.8–8.3μM, while none of the tested compounds showed any significant effect on inhibiting TNF-α release.

Fast and Facile Synthesis of 4-Nitrophenyl 2-Azidoethylcarbamate Derivatives from N-Fmoc-Protected α-Amino Acids as Activated Building Blocks for Urea Moiety-Containing Compound Library.

A fast and facile synthesis of a series of 4-nitrophenyl 2-azidoethylcarbamate derivatives as activated urea building blocks was developed. The N-Fmoc-protected 2-aminoethyl mesylates derived from various commercially available N-Fmoc-protected α-amino acids, including those having functionalized side chains with acid-labile protective groups, were directly transformed into 4-nitrophenyl 2-azidoethylcarbamate derivatives in 1 h via a one-pot two-step reaction. These urea building blocks were utilized for the preparation of a series of urea moiety-containing mitoxantrone-amino acid conjugates in 75-92% yields and parallel solution-phase synthesis of a urea compound library consisted of 30 members in 38-70% total yields.

Solution-phase microwave assisted parallel synthesis, biological evaluation and in silico docking studies of N,N′-disubstituted thioureas derived from 3-chlorobenzoic acid

A facile and robust microwave-assisted solution phase parallel synthesis protocol was exercised for the development of a 38-member library of N,N′-disubstituted thiourea analogues (1–38) by using an identical set of conditions. The reaction time for synthesis of N,N′-disubstituted thiourea analogues was drastically reduced from a reported duration of 8–12h for conventional methods to only 1.5–2.0min. All the derivatives (1–38) were characterized by physico-analytical techniques such as elemental analysis in combination with FT-IR, 1H, 13C NMR and by single crystal XRD analysis have also been performed. These compounds were screened for their in vitro urease inhibition activities. Majority of compounds exhibited potent urease inhibition activities, however, the most significant activity was found for 16, with an IC50 value of 1.23±0.1μM. Furthermore, the synthesized compounds were screened for their cytotoxic potential against lungs cancer cell lines. Cell culture studies demonstrated significant toxicity of the compounds on the cell lines, and the levels of toxicity were altered in the presence of various side groups. The molecular docking studies of the most potent inhibitors were performed to identify the probable binding modes in the active site of the urease enzymes. These compounds have a great potential and significance for further investigations.

Sucrose and KF quenching system for solution phase parallel synthesis.

The KF, sucrose (table sugar) exploited as quenching system in solution phase parallel synthesis. Excess of electrophiles were covalently trapped with hydroxyl functionality of sucrose and due to polar nature of sucrose derivative was solubilize in water. Potassium fluoride used to convert various excess electrophilic reagents such as acid chlorides, sulfonyl chlorides, isocyanates to corresponding fluorides, which are less susceptible for hydrolysis and subsequently sucrose traps these fluorides and dissolves them in water thus removing them from reaction mixture. Various excess electrophilic reagents such as acid chlorides, sulfonyl chlorides, and isocyanates were quenched successfully to give pure products in excellent yields.

Efficient Construction of Azaspiro[4.5]trienone Libraries via Tandem Ugi 4CC/Electrophilic ipso-Iodocyclization in One-Pot.

A solution-phase parallel synthesis of pharmaceutically important azaspiro[4.5]trienones has been developed by performing tandem Ugi four-component condensation (U4CC), involving substituted p-anisidines, aldehydes, 3-alkyl/aryl-propiolic acids, and isocyanides, and iodine-mediated ipso-iodocyclization in one-pot. This highly atom economical process produced functionalized azaspiro[4.5]trienones in good to excellent overall yields and products were easily isolated by precipitation followed by crystallization. These vinyl-iodide bearing azaspiro[4.5]trienones were utilized for further modifications through Suzuki coupling and deiodination reaction to demonstrate the suitability of these products for various palladium catalyzed modifications. The present method provides an easy access to highly functionalized azaspiro[4.5]trienones that can be useful in drug discovery research.

Design and Synthesis of a Screening Library Using the Natural Product Scaffold 3-Chloro-4-hydroxyphenylacetic Acid.

The fungal metabolite 3-chloro-4-hydroxyphenylacetic acid (1) was utilized in the generation of a unique drug-like screening library using parallel solution-phase synthesis. A 20-membered amide library (3-22) was generated by first converting 1 to methyl (3-chloro-4-hydroxyphenyl)acetate (2), then reacting this scaffold with a diverse series of primary amines via a solvent-free aminolysis procedure. The structures of the synthetic analogues (3-22) were elucidated by spectroscopic data analysis. The structures of compounds 8, 12, and 22 were confirmed by single X-ray crystallographic analysis. All compounds were evaluated for cytotoxicity against a human prostate cancer cell line (LNCaP) and for antiparasitic activity toward Trypanosoma brucei brucei and Plasmodium falciparum and showed no significant activity at 10 μM. The library was also tested for effects on the lipid content of LNCaP and PC-3 prostate cancer cells, and it was demonstrated that the fluorobenzyl analogues (12-14) significantly reduced cellular phospholipid and neutral lipid levels.

Solution-phase parallel synthesis of ruxolitinib-derived Janus kinase inhibitors via copper-catalyzed azide-alkyne cycloaddition.

A solution-phase parallel synthesis of triazole-derived ruxolitinib analogues was developed in the current study. The method employs copper-catalyzed azide-alkyne cycloaddition to build up the central triazole template. Product isolation by precipitation and centrifugation is straightforward and yields high purity compounds suited for biological profiling. A simple protocol for accessing the terminal alkyne precursors in high yields was established and a library of ruxolitinib-like triazoles featuring diverse functional groups was prepared. In addition, a model for the binding mode of ruxolitinib to Janus kinase (JAK) 2 is proposed. In contrast to previous models, the pose explains the compound selectivity for JAK1/JAK2 and is in accordance with published structure-activity data. On this basis, a structure-based design hypothesis for inverting the selectivity profile of ruxolitinib is deduced. Application of this strategy identified a moderately potent JAK3 inhibitor (35 nM) with high selectivity against other JAKs, potentially exploiting a covalent binding mode.

Tuning transthyretin amyloidosis inhibition properties of iododiflunisal by combinatorial engineering of the nonsalicylic ring substitutions.

Two series of iododiflunisal and diflunisal analogues have been obtained by using a two step sequential reaction solution-phase parallel synthesis. The synthesis combined an aqueous Suzuki-Miyaura cross-coupling and a mild electrophilic aromatic iodination step using a new polymer-supported iodonium version of Barluenga's reagent. From a selected set of 77 noniodinated and 77 iodinated diflunisal analogues, a subset of good transthyretin amyloid inhibitors has been obtained with improved turbidimetry inhibition constants, high binding affinity to transthyretin, and good selectivity for TTR compared to other thyroxine binding proteins.

Solution-phase parallel synthesis of aryloxyimino amides via a novel multicomponent reaction among aromatic (Z)-chlorooximes, isocyanides, and electron-deficient phenols.

A library of 41 aryloxyimino amides was prepared via solution phase parallel synthesis by extending the multicomponent reaction of (Z)-chlorooximes and isocyanides to the use of electron-deficient phenols. The resulting aryloxyiminoamide derivatives can be used as intermediates for the synthesis of benzo[d]isoxazole-3-carboxamides, dramatically reducing the number of synthetic steps required by other methods reported in literature.

Solution-phase parallel synthesis of acyclic nucleoside libraries of purine, pyrimidine, and triazole acetamides.

Molecular diversity plays a pivotal role in modern drug discovery against phenotypic or enzyme-based targets using high throughput screening technology. Under the auspices of the Pilot Scale Library Program of the NIH Roadmap Initiative, we produced and report herein a diverse library of 181 purine, pyrimidine, and 1,2,4-triazole-N-acetamide analogues which were prepared in a parallel high throughput solution-phase reaction format. A set of assorted amines were reacted with several nucleic acid N-acetic acids utilizing HATU as the coupling reagent to produce diverse acyclic nucleoside N-acetamide analogues. These reactions were performed using 24 well reaction blocks and an automatic reagent-dispensing platform under inert atmosphere. The targeted compounds were purified on an automated purification system using solid sample loading prepacked cartridges and prepacked silica gel columns. All compounds were characterized by NMR and HRMS, and were analyzed for purity by HPLC before submission to the Molecular Libraries Small Molecule Repository (MLSMR) at NIH. Initial screening through the Molecular Libraries Probe Production Centers Network (MLPCN) program, indicates that several analogues showed diverse and interesting biological activities.

Synthesis and Library Construction of Privileged Tetra-Substituted Δ5-2-Oxopiperazine as β-Turn Structure Mimetics

In this study, we developed an efficient and practical procedure for the synthesis of tetra-substituted Δ5-2-oxopiperazine that mimics the bioactive β-turn structural motif of proteins. This synthetic route is robust and modular enough to accommodate four different substituents to obtain a high level of molecular diversity without any deterioration in stereochemical enrichment of the natural and unnatural amino acids. Through the in silico studies, including a distance calculation of side chains and a conformational overlapping of our model compound with a native β-turn structure, we successfully demonstrated the conformational similarity of tetra-substituted Δ5-2-oxopiperazine to the β-turn motif. For the library construction in a high-throughput manner, the fluorous tag technology was adopted with the use of a solution-phase parallel synthesis platform. A 140-membered pilot library of tetra-substituted Δ5-2-oxopiperazines was achieved with an average purity of 90% without further purification.

Solution-phase microwave assisted parallel synthesis of N,N′-disubstituted thioureas derived from benzoic acid: Biological evaluation and molecular docking studies

An efficient and facile microwave-assisted solution phase parallel synthesis for a 26-member library of N,N′-disubstituted thiourea analogs were accomplished successfully. The reaction time for synthesis of analogs was drastically reduced from a reported 8–12 h to only 10 min. Compounds were more than 95% pure, as characterized by modern analytical techniques, i.e. 1H &13C NMR and FT-IR. The solid phase structural analysis has also been performed by single crystal XRD analysis. Synthesized compounds were preliminary screened for their in vitro urease inhibition and antifungal activity. Most of the compounds were found to be potent inhibitors of urease. However, the most significant activity was found for 11 with IC50 of 1.67 μM. The docking scores correlate with the IC50 values of inhibitors.

Diversity by Divergence: Solution-Phase Parallel Synthesis of a Library of N-Diversified 1-Oxa-7-Azaspiro[4.5]decan-2-yl-Propanes and -Butanes

The synthesis of a 162-member compound library derived from a single precursor via a multistage divergence strategy is described. Divergence is sequentially introduced in three ways: (1) by early preparation of two separable spirocyclic diastereomers, (2) by elaboration of each spirocyclic diastereomer to a different scaffold using four Horner-Emmons-Wadsworth reagents, and (3) by employing three different modes of nitrogen diversification with each scaffold to afford the final compounds. This 2 diastereomers × 4 reagents × 3 modes of diversification strategy leads to 24 unique synthetic pathways that ultimately afforded, in parallel format, the 162-compound set.

Disubstituted 1-Aryl-4-Aminopiperidine Library Synthesis Using Computational Drug Design and High-Throughput Batch and Flow Technologies

A platform that incorporates computational library design, parallel solution-phase synthesis, continuous flow hydrogenation, and automated high throughput purification and reformatting technologies was applied to the production of a 120-member library of 1-aryl-4-aminopiperidine analogues for drug discovery screening. The application described herein demonstrates the advantages of computational library design coupled with a flexible, modular approach to library synthesis. The enabling technologies described can be readily adopted by the traditional medicinal chemist without extensive training and lengthy process development times.

A solution-phase parallel synthesis of alkylated guanidines from thioisocyanates and amines

An efficient solution-phase parallel synthesis of alkylated guanidines from commercial thioisocyanates and amines is described. In the first step, a thioisocyanate reacts with one equivalent of ammonia or a primary or secondary amine to give a thiourea intermediate. The latter is S-alkylated with n-dodecyl bromide resulting in the corresponding thiouronium bromide. Finally, the reaction of the thiouronium salt with a second equivalent of ammonia or a primary amine yields an alkylated guanidine. All three synthetic steps are easily combined in a one-pot high-yielding procedure with a simple work-up. Ca. 250 guanidine derivatives with high structural and functional diversity were synthesized by the developed method. 35 representatives reported in this study were fully characterized.