A fast and efficient protocol for the generation of substituted 5-arylidene rhodanines in a sequential one-pot two-step process combining the "Holmberg method" and the Knoevenagel condensation under microwave-assisted co...A fast and efficient protocol for the generation of substituted 5-arylidene rhodanines in a sequential one-pot two-step process combining the "Holmberg method" and the Knoevenagel condensation under microwave-assisted conditions has been developed. The final compounds 11a-k have been obtained in high yield and purity after a simple precipitation from methanol, making this procedure facile, practical, and rapid to execute.
The silica gel-catalyzed synthesis of 5-amino-2-aryl-3H-chromeno[4,3,2-de][1,6]naphthyridine-4-carbonitriles and 5-amino-2-aryl-3H-quinolino[4,3,2-de][1,6]naphthyridine-4-carbonitriles were simply achieved upon the one-p...The silica gel-catalyzed synthesis of 5-amino-2-aryl-3H-chromeno[4,3,2-de][1,6]naphthyridine-4-carbonitriles and 5-amino-2-aryl-3H-quinolino[4,3,2-de][1,6]naphthyridine-4-carbonitriles were simply achieved upon the one-pot cascade reaction of malononitrile with substituted 2-hydroxyacetophenone (or 2-aminoacetophenone) and aromatic aldehyde in aqueous media. The mechanistic investigation results based on electrospray ionization mass spectrometry (ESI-MS) indicated that malononitrile displayed a dual role during this transformation. Thirteen bonds were cleaved and 12 new bonds were constructed in the formation of 5-amino-2-aryl-3H-chromeno[4,3,2-de][1,6]naphthyridine-4-carbonitriles, while only 2 H(2)O molecules were removed. The fluorescence properties screening showed five new compounds have high fluorescence quantum yields.
A fluorous linker-assisted synthetic protocol has been developed for preparation of sclerotigenin-type benzodiazepine-quinazolinone library containing 144 analogues. Amide coupling of fluorous trimethoxybenzyl (TMB)-prot...A fluorous linker-assisted synthetic protocol has been developed for preparation of sclerotigenin-type benzodiazepine-quinazolinone library containing 144 analogues. Amide coupling of fluorous trimethoxybenzyl (TMB)-protected amino esters with anthranilic acids followed by base-promoted cyclizations afforded 4-benzodiazepine-2,5-diones. Further derivatization of benzodiazepinediones by reacting with azidobenzoyl chlorides, cyclization, and fluorous linker cleavage afforded the desired compound library. The reaction intermediates were purified by fluorous solid-phase extraction (F-SPE) and final products were further purified by prep-HPLC.
A domino Horner-Wadsworth-Emmons olefination strategy has been used to prepare homologous series of (polyen)ones, and through combinatorial elaboration, corresponding families of highly branched hydrocarbons. Gas chromat...A domino Horner-Wadsworth-Emmons olefination strategy has been used to prepare homologous series of (polyen)ones, and through combinatorial elaboration, corresponding families of highly branched hydrocarbons. Gas chromatography-mass spectrometry of the mixtures has enabled the rapid and unambiguous identification of several highly branched alkanes of geochemical importance. This is the first example of the use of combinatorial synthesis for the elucidation of structural connectivity.
An efficient and practical method has been manifested for the diversity-oriented synthesis of quinolines via Friedländer annulation reaction for the generation of a wide range of structurally interesting and pharmacologi...An efficient and practical method has been manifested for the diversity-oriented synthesis of quinolines via Friedländer annulation reaction for the generation of a wide range of structurally interesting and pharmacologically significant compounds by using ceric ammonium nitrate as a catalyst (10 mol %) at ambient temperature in 45 min. A variety of functional groups are introduced at various positions of the quinoline moiety, and further the diversity of the core skeleton was expanded at R(1) and R(2) positions by the synthesis of various hybrids. Initial screening of the compounds for cytotoxicity against a series of cancer cell lines showed promising results.
The solution-phase parallel synthesis of a 136-member library of isoxazol(in)e-CH(2)-pyrazoles is described. X-ray crystallographic structure determination verified the regioselectivities of the N-alkylation and nitrile...The solution-phase parallel synthesis of a 136-member library of isoxazol(in)e-CH(2)-pyrazoles is described. X-ray crystallographic structure determination verified the regioselectivities of the N-alkylation and nitrile oxide 1,3-dipolar cycloaddition steps. The construction of these pharmaceutically relevant heterocycles on solid support under microwave irradiation is also demonstrated. The resulting library of drug-like compounds has been added to the National Institutes of Health repository (approximately 10 mg of each with >or=90% purity) for pilot-scale biomedical studies with bioassay data available at the National Center for Biotechnology Information PubChem database. A subset of these compounds has been broadly screened by Dow AgroSciences for herbicidal, fungicidal, and insecticidal activity.
A small library of fluorescent and unsymmetrical trans-stilbene compounds was efficiently produced by a solid-phase synthetic approach using the sulfonate-based traceless linker system. Nickel(0)-catalyzed cleavage/cross...A small library of fluorescent and unsymmetrical trans-stilbene compounds was efficiently produced by a solid-phase synthetic approach using the sulfonate-based traceless linker system. Nickel(0)-catalyzed cleavage/cross-coupling of polymer-bound stilbenesulfonates with aryl Grignard reagents generated the desired trans-stilbenes at high yield by the multifunctional release facilitating the additional diversification of the library. The luminescent properties of trans-stilbenes are assessed, and the influence of alkyl substituents on their photophysical properties is discussed.
Amino alcohols, diamines, benzenesulfonyl chlorides, and bromoketones were used to prepare polymer-supported 2-(2-(2-(amino/hydroxyl)ethylamino)ethyl)-3-benzoyl-2H-indazoles. Acid-mediated release yielded 2-((amino/hydro...Amino alcohols, diamines, benzenesulfonyl chlorides, and bromoketones were used to prepare polymer-supported 2-(2-(2-(amino/hydroxyl)ethylamino)ethyl)-3-benzoyl-2H-indazoles. Acid-mediated release yielded 2-((amino/hydroxyl)ethyl)-1-aryl-3,4-dihydropyrazino[1,2-b]indazole-2-iums. In neutral pH, iminiums spontaneously cyclized to complex fused heterocycles 3,6,9,10-tetraazatetracyclo[7.7.0.0(2,6).0(11,16)]hexadeca-11,13,15-trienes, 3-oxa-6,9,10-triazatetracyclo[7.7.0.0(2,6).0(11,16)]hexadeca-11,13,15-trienes, and 3,7,10,11-tetraazatetracyclo[8.7.0.0(2,7).0(12,17)]heptadeca-12,14,16-trienes. Transformations were carried out under mild conditions and tolerated diverse substitution patterns.
Cyanoacetic acid derivatives are the starting materials for a plethora of multicomponent reaction (MCR) scaffolds. Here we describe valuable general protocols for the synthesis of arrays of 2-aminothiophene-3-carboxamide...Cyanoacetic acid derivatives are the starting materials for a plethora of multicomponent reaction (MCR) scaffolds. Here we describe valuable general protocols for the synthesis of arrays of 2-aminothiophene-3-carboxamides from cyanoacetamides, aldehydes or ketones, and sulfur via a Gewald-3CR variation. In many cases the reactions involve a very convenient work up by simple precipitation in water and filtration. More than 40 new products are described. We foresee our protocol and the resulting derivatives to become very valuable to greatly expanding the MCR scaffold space of cyanoacetamide derivatives.
A solid-phase synthesis of 5-aminopyrazole has been developed and applied to the preparation of pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones. In this strategy, a one-pot reaction from 5-aminopyrazoles to the pyrazolo[5,1...A solid-phase synthesis of 5-aminopyrazole has been developed and applied to the preparation of pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones. In this strategy, a one-pot reaction from 5-aminopyrazoles to the pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones which provided the compounds in good yields was demonstrated. Using this synthetic strategy, we prepared a representative set of 16 pyrazolo[5,1-d][1,2,3,5]tetrazine-4(3H)-ones.
Libraries of benzoxanthenes, as well as of benzochromenes, were efficiently synthesized via one-pot, three-component reactions of 2-naphthol, aldehydes, and cyclic 1,3-diketones/malononitrile/ethyl cyanoacetate in the pr...Libraries of benzoxanthenes, as well as of benzochromenes, were efficiently synthesized via one-pot, three-component reactions of 2-naphthol, aldehydes, and cyclic 1,3-diketones/malononitrile/ethyl cyanoacetate in the presence of catalytic amount of ceric ammonium nitrate (CAN) under solvent free conditions. The protocol offers rapid synthesis of structurally diverse benzoxanthenes and benzochromenes for biologically screening. All the synthesized compounds were evaluated for their anti-proliferative activity, and several compounds were exhibiting promising anti-proliferative activity.
The one pot synthesis of a new fused 1,2,5-triazepine-3,6-diones, 1,2,5-triazepine-3,7-diones heterocyles has been described via Petasis reactions. These heterocycles might be suitable for elaboration into larger peptide...The one pot synthesis of a new fused 1,2,5-triazepine-3,6-diones, 1,2,5-triazepine-3,7-diones heterocyles has been described via Petasis reactions. These heterocycles might be suitable for elaboration into larger peptides at amino termini. The scope and limitations of this method have been examined.
Traceless solid-phase synthesis of 2,5,6,7-tetrasubstituted thiazolo[4,5-b]pyridine derivatives is described. Thorpe-Ziegler type cyclization of solid supported cyanocarbonimidodithioate with alpha-halo ketones afforded...Traceless solid-phase synthesis of 2,5,6,7-tetrasubstituted thiazolo[4,5-b]pyridine derivatives is described. Thorpe-Ziegler type cyclization of solid supported cyanocarbonimidodithioate with alpha-halo ketones afforded thiazole resin, which were converted to the desired thiazolopyridine resin by the Friedländer protocol under microwave irradiation conditions. After oxidation of sulfides to sulfones, nucleophilic desulfonative substitution with amines gave the target thiazolo[4,5-b]pyridine derivatives in good overall yields.
A small molecule library of alkyl, sulfone, and carboxamide functionalized pyrazoles and isoxazoles has been developed via a rapid sequential condensation of various alpha-acylketene dithioacetals (1a-o) with hydrazine h...A small molecule library of alkyl, sulfone, and carboxamide functionalized pyrazoles and isoxazoles has been developed via a rapid sequential condensation of various alpha-acylketene dithioacetals (1a-o) with hydrazine hydrate or hydroxylamine hydrochloride, followed by oxidation of sulfide to sulfone using water as the reaction medium. An efficient and safe oxidation of sulfides (4/5a-o) to the corresponding sulfones (6/7a-o) using sodium per borate system in aqueous medium is reported. The concise and two step synthesis of trisubstituted pyrazoles and isoxazoles was investigated under variety of reaction condition. The newly developed methodology has the advantage of excellent yield and chemical purity with short reaction time using water as a solvent.
Versatile and novel reactions of 5-aminotetrazole with structurally diverse aryl aldehydes and building blocks with active methylene catalyzed by iodine were investigated in a multicomponent one-pot protocol. A series of...Versatile and novel reactions of 5-aminotetrazole with structurally diverse aryl aldehydes and building blocks with active methylene catalyzed by iodine were investigated in a multicomponent one-pot protocol. A series of 5,7-diaryl-4,7-dihydrotetrazolo[1,5-a]pyrimidines C and 5-methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylates D were obtained in moderate to good yields. Further exploration rapidly afforded various E in good to excellent yields; in addition, compound F was also obtained under the same condition. The structures of products were characterized by LC-MS, (1)H NMR, (13)C NMR, and elemental analysis.
A new protocol in which cyclohexylisocyanide and methyl 2-isocyanoacetate are used as convertible isocyanides for Ugi/de-Boc/cyclization/Suzuki synthesis of biaryl-substituted 1,4-benzodiazepine-2,5-diones has been devel...A new protocol in which cyclohexylisocyanide and methyl 2-isocyanoacetate are used as convertible isocyanides for Ugi/de-Boc/cyclization/Suzuki synthesis of biaryl-substituted 1,4-benzodiazepine-2,5-diones has been developed. Ugi reactions of Boc-protected anthranilic acids, fluorous benzaldehydes, amines, and cyclohexylisocyanide or methyl 2-isocyanoacetate were carried out at room temperature. Microwave-promoted de-Boc/cyclization reactions afforded 1,4-benzodiazepine-2,5-diones (BZDs). Suzuki coupling reactions further derivatized the BZD ring by removing the fluorous tag and introducing the biaryl group. A thirty three-member biaryl-substituted BZD library containing four points of diversity was prepared by microwave-assisted solution-phase fluorous parallel synthesis.
In this work, two novel isocyanide-based multicomponent reactions of 1,2-diamine compounds with diketene have been developed as efficient strategies for the synthesis of 2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepine-2-car...In this work, two novel isocyanide-based multicomponent reactions of 1,2-diamine compounds with diketene have been developed as efficient strategies for the synthesis of 2,3,4,5-tetrahydro-1H-benzo[b][1,4]diazepine-2-carboxamides with regiochemical control and 1,6-dihydropyrazine-2,3-dicarbonitriles in good to excellent yields at ambient temperature.
The increase in the incidence of antibiotic-resistant infections is a major concern to healthcare workers and requires the development of novel antibacterial agents. Recently, we described a series of benzophenone-contai...The increase in the incidence of antibiotic-resistant infections is a major concern to healthcare workers and requires the development of novel antibacterial agents. Recently, we described a series of benzophenone-containing antibiotics which displayed activity against antibiotic-resistant bacteria. We have shown that these agents function by disrupting the bacterial membrane. To further explore these compounds, a practical and efficient solution-phase parallel synthesis method was developed which allowed us to prepare combinatorial libraries of these agents. Using this method, we prepared 218 compounds in 58 reactions. All of the compounds were characterized by HPLC and MALDI-TOF mass spectrometry. Analysis of this library for antibacterial activity identified six compounds which displayed MIC values of 2.0 mg/L against Staphylococcus aureus. Examination of the structure-function relationships of these agents revealed that cationic groups were required and that cyclic, aliphatic amines were crucial for activity. Using the information generated here, we speculate on how the various structural features of the molecule are necessary for the interaction with the bacterial membrane.
Instead of using diversity oriented syntheses (DOS) to obtain compounds with biological activities, we employed the DOS method to efficiently obtain multifunctional single attachment point (MSAP) reagents for the conjuga...Instead of using diversity oriented syntheses (DOS) to obtain compounds with biological activities, we employed the DOS method to efficiently obtain multifunctional single attachment point (MSAP) reagents for the conjugation to proteins. Acid insensitive functional groups (chelators, fluorochromes) were attached to Lys-Cys-NH(2) or Lys-Lys-betaAla-Cys-NH(2) peptide scaffolds. After cleavage from solid supports, the modified peptide intermediates were split and further modified by two solution phase, chemoselective reactions employing the single amine and single thiol presented on the intermediates. MSAP-based fluorochrome-chelates were obtained, some possessing a third functional group like a polyethylene glycol (PEG) polymer or "click chemistry" reactive alkynes and azides. The DOS of MSAP reagents permitted the efficient generation of panels of MSAP reagents that can be used to obtain multifunctional proteins with a single modified amino acid (a single attachment point).