Heterocyclic HIV-1 protease inhibitors

N-Heterocycles as Promising Antiviral Agents: A Comprehensive Overview

Viruses are a real threat to every organism at any stage of life leading to extensive infections and casualties. N-heterocycles can affect the viral life cycle at many points, including viral entrance into host cells, viral genome replication, and the production of novel viral species. Certain N-heterocycles can also stimulate the host's immune system, producing antiviral cytokines and chemokines that can stop the reproduction of viruses. This review focused on recent five- or six-membered synthetic N-heterocyclic molecules showing antiviral activity through SAR analyses. The review will assist in identifying robust scaffolds that might be utilized to create effective antiviral drugs with either no or few side effects.

Thermal and Microwave-Assisted Synthesis of New Highly Functionalized Bis-β-lactams from Available Compounds via Bisketene as an Intermediate

The synthesis of highly functionalized bis-β-lactams containing aromatic rings was achieved by thermal and microwave-assisted methods starting from easily available 2-(4-hydroxyphenyl)acetic acid and 2,2'-(propane-2,2-diyl)diphenol precursors. The approach to these valuable heterocyclic scaffolds involved formal [2π + 2π] cycloadditions between Schiff bases and novel bisketenes, which were generated in situ, followed by an electrocyclic reaction of zwitterionic intermediates. Reactions carried out under microwave irradiation were clean and gave high yields with significantly reduced reaction times. Interestingly, in the thermal method, the reaction proceeded in a stereospecific manner, and only the trans-cis or cis-cis isomers were formed. However, under the microwave conditions, the reaction proceeded stereoselectively, and other possible isomers such trans-trans and cis-trans isomers were formed in addition to the product formed under thermal conditions. More interestingly, when the two compounds that did not produce any products under thermal conditions were reacted under microwave conditions, one formed the trans-cis isomer and the other formed the cis-trans and trans-trans isomers as two products .

Ferrocenyl thiazolidine-2-thione ornamented 1D coordination polymers derived from coinage metal halides and pseudohalides

Three new ferrocene-functionalized thiazolidine-2-thione coinage metal coordination polymers with halides and pseudo-halides were synthesized and the nature of their weak interactions was assessed.

An Inhibitor of Fatty Acid Synthase Thioesterase Domain with Improved Cytotoxicity against Breast Cancer Cells and Stability in Plasma

It is well recognized that many cancers are addicted to a constant supply of fatty acids (FAs) and exhibit brisk de novo FA synthesis. Upregulation of a key lipogenic enzyme, fatty acid synthase (FASN), is a near-universal feature of human cancers and their precursor lesions, and has been associated with chemoresistance, tumor metastasis, and diminished patient survival. FASN inhibition has been shown to be effective in killing cancer cells, but progress in the field has been hindered by off-target effects and poor pharmaceutical properties of candidate compounds. Our initial hit (compound 1) was identified from a high-throughput screening effort by the Sanford-Burnham Center for Chemical Genomics using purified FASN thioesterase (FASN-TE) domain. Despite being a potent inhibitor of purified FASN-TE, compound 1 proved highly unstable in mouse plasma and only weakly cytotoxic to breast cancer (BC) cells in vitro. An iterative process of synthesis, cytotoxicity testing, and plasma stability assessment was used to identify a new lead (compound 41). This lead is more cytotoxic against multiple BC cell lines than tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic acid (the literature standard for inhibiting FASN), is stable in mouse plasma, and shows negligible cytotoxic effects against nontumorigenic mammary epithelial cells. Compound 41 also has drug-like physical properties based on Lipinski's rules and is, therefore, a valuable new lead for targeting fatty acid synthesis to exploit the requirement of tumor cells for fatty acids. SIGNIFICANCE STATEMENT: An iterative process of synthesis and biological testing was used to identify a novel thioesterase domain FASN inhibitor that has drug-like properties, is more cytotoxic to breast cancer cells than the widely used tetrahydro-4-methylene-2S-octyl-5-oxo-3R-furancarboxylic acid, and has negligible effects on the growth and proliferation of noncancerous mammary epithelial cells. Our studies have confirmed the value of using potent and selective FASN inhibitors in the treatment of BC cells and have shown that the availability of exogenous lipoproteins may impact both cancer cell FA metabolism and survival.

Efficient synthesis of novel β-sitosterol scaffolds containing 1,2,3-triazole via copper(I)-catalyzed click reaction under microwave irradiation

In this work, new derivatives of the β-sitosterol scaffolds containing 1,2,3-triazole are prepared by the reaction of β-sitosterol with aromatic alkynes via copper(I)-catalyzed azide-alkyne cycloaddition reactions under microwave irradiation. The reaction has several advantages including high yields, short reaction times, and a simple work-up procedure.

One-pot synthesis of fused benzoxazino[1,2,3]triazolyl[4,5-c]quinolinone derivatives and their anticancer activity

Cu/Pd catalyzed one pot synthesis of fused benzoxazino[1,2,3]triazolyl[4,5-c]quinolinone hybrids and their cytotoxic activity against human cancer cell lines MCF-7, HeLa and A-549 is described.

An efficient CuI/DBU-catalyzed one-pot protocol for synthesis of 1,4-disubstituted 1,2,3-triazoles

A convenient CuI/DBU catalyzed one-pot method has been developed for the synthesis of 1,4-disubstituted 1,2,3-triazoles from aryl iodides, sodium azide and phenylacetaldehyde derivatives or from aryl iodides, sodium azide and alkynes in DMSO.

Enamine/enolate-mediated organocatalytic azide-carbonyl [3+2] cycloaddition reactions for the synthesis of densely functionalized 1,2,3-triazoles

Organocatalytic click! Recent advances in the metal-free enamine/enolate-mediated azide-carbonyl [3+2] cycloaddition reaction are discussed. These approaches require neither a metal catalyst nor alkyne substrates. Owing to the ready availability of carbonyl compounds, these methods thus offer excellent alternatives for the synthesis of 1,4-/1,5-disubstituted and 1,4,5-trisubstituted 1,2,3-triazoles.

I2/TBPB mediated oxidative reaction of N-tosylhydrazones with anilines: practical construction of 1,4-disubstituted 1,2,3-triazoles under metal-free and azide-free conditions

An efficient I2 (20 mol %)/TBPB mediated oxidative formal [4 + 1] cycloaddition of N-tosylhydrazones with anilines via C-N/N-N bond formation and S-N cleavage has been developed. This protocol represents a simple, general, and efficient approach for the construction of 1,2,3-triazoles under metal-free and azide-free conditions by utilizing a catalytic amount of I2.

Synthesis and evaluation of imidazole-4,5- and pyrazine-2,3-dicarboxamides targeting dengue and yellow fever virus

The results of a high-throughput screening assay using the dengue virus-2 replicon showed that the imidazole 4,5-dicarboxamide (I45DC) derivative (15a) has a high dengue virus inhibitory activity. Based on 15a as a lead compound, a novel class of both disubstituted I45DCs and the resembling pyrazine 2,3-dicarboxamides (P23DCs) were synthesized. Here, we report on their in vitro inhibitory activity against dengue virus (DENV) and yellow fever virus (YFV). Some of these first generation compounds have shown activity against both viruses in the micromolar range. Within this series, compound 15b was observed to display the highest antiviral potency against YFV with an EC₅₀ = 1.85 μM. In addition, compounds 20a and 20b both potently inhibited replication of DENV (EC₅₀ = 0.93 μM) in Vero cells.

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Two new series of heterocycles were evaluated for Flavivirus inhibition.

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Activities at micromolar levels were noted for inhibition of dengue virus.

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Remarkable selective inhibitory properties for yellow fever virus were recorded.

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Imidazole-4,5-dicarboxylic amides provide an interesting scaffold for antivirals.

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Pyrazine-2,3-dicarboxylic amides likewise are endowed with anti-flavivirus activities.

An organocatalytic azide-aldehyde [3+2] cycloaddition: high-yielding regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles

An organocatalytic azide-aldehyde [3+2] cycloaddition (organo-click) reaction of a variety of enolizable aldehydes is reported. The organo-click reaction is characterized by a high rate and regioselectivity, mild reaction conditions, easily available substrates with simple operation, and excellent yields with a broad spectrum of substrates. It constitutes an alternative to the previously known CuAAC, RuAAC, and IrAAC click reactions.

Non-asymmetric organocatalysis

Asymmetric organocatalysis is now an established methodology for the preparation of chiral compounds. However, these are not the only valuable molecules which can be conveniently obtained. Organocatalytic reactions affording achiral compounds are gaining momentum, opening unexplored pathways in the synthesis of densely functionalized aromatic moieties, olefins and useful molecules such as natural substances.

Poly[[μ(2)-aqua-μ(3)-(4-carb-oxy-2-propyl-1H-imidazole-5-carboxyl-ato-κN,O:O:O)-sodium] hemihydrate]

In the title compound, {[Na(C(8)H(9)N(2)O(4))(H(2)O)]·0.5H(2)O}(n), the Na(+) ion is coordinated by two bridging water mol-ecules, one N atom and three O atoms from three 4-carb-oxy-2-propyl-1H-imidazole-5-carboxyl-ate (H(2)pimdc) ligands. Adjacent Na(+) ions are linked alternately by two water O atoms and two carb-oxy O atoms into a chain along [001]. These chains are connected through the coordination of the carboxyl-ate O atoms to the Na(+) ions, forming a three-dimensional structure. An intra-molecular O-H⋯O hydrogen bond and inter-molecular N-H⋯O and O-H⋯O hydrogen bonds are present in the crystal structure.

4,4'-Bipyridine-2-hydroxy-propane-1,2,3-tricarboxylic acid (3/2)

The combination of 2-hydroxy­propane-1,2,3-tricarboxylic acid (H₃hypta, also called citric acid) and 4,4′-bipyridine (4,4′-bipy) in a 1:1.5 molar ratio leads to the formation of the title mol­ecular cocrystal, 1.5C₁₀H₈N₂·C₆H₈O₇. The asymmetric unit contains one and a half 4,4′-bipy units, with one lying across a centre of inversion, and one H₃hypta mol­ecule. The significant differences in the C—O bond distances support the existence of the un-ionized acid mol­ecule and confirm the formation of a cocrystal. There are π–π and C—H⋯π stacking inter­actions between the aromatic rings of 4,4′-bipy [with inter­planar distances of 3.7739 (8) and 3.7970 (8) Å] and between CH groups of H₃hypta [with an H⋯π distance of 2.63 Å]. In the crystal structure, intermolecular O—H⋯N hydrogen bonds occur and an O—H⋯O hydrogen bond occurs within the citric acid moiety.

Parallel synthesis of a library of symmetrically- and dissymmetrically-disubstituted imidazole-4,5-dicarboxamides bearing amino acid esters

The imidazole-4,5-dicarboxylic acid scaffold is readily derivatized with amino acid esters to afford symmetrically- and dissymmetrically-disubstituted imidazole-4,5-dicarboxamides with intramolecularly hydrogen bonded conformations that predispose the presentation of amino acid pharmacophores. In this work, a total of 45 imidazole-4,5-dicarboxamides bearing amino acid esters were prepared by parallel synthesis. The library members were purified by column chromatography on silica gel and the purified compounds characterized by LC-MS with LC detection at 214 nm. A selection of the final compounds was also analyzed by (1)H-NMR spectroscopy. The analytically pure final products have been submitted to the Molecular Library Small Molecule Repository (MLSMR) for screening in the Molecular Library Screening Center Network (MLSCN) as part of the NIH Roadmap.

Intramolecular hydrogen bond strength and pK(a) determination of N,N'-disubstituted imidazole-4,5-dicarboxamides

N,N'-Disubstituted imidazole-4,5-dicarboxamides (I45DCs) form an intramolecular hydrogen bond worth an estimated 14 +/- 1 kcal/mol, as measured with a model structure in DMSO-d6 at 3 mM, thereby predisposing the molecular conformation to a folded rather than extended form. The I45DCs also show evidence of aggregation in both CDCl3 (>1 mM) and DMSO-d6 (>10 mM) solutions. These compounds are uncharacteristically weak bases in comparison with imidazoles bearing similar electron-withdrawing groups.

Heterocyclic Thionates as a New Class of Bridging Ligands in Oxo-Centered Triangular Cyclopentadienylchromium(III) Complexes

The interactions of the benzothiazolate complex, CpCr(CO)(2)(SCSN(C(6)H(4))) (2), and the tetrazole thiolate complex, CpCr(CO)(3)(eta(1)-SCN(4)Ph) (3), with controlled amounts of Me(3)OBF(4) and (MeO)(2)SO(2), respectively, produced the corresponding mu(3)-oxo trinuclear thionate-bridged complexes, [Cp(3)Cr(3)(mu(2)-OH)(mu(3)-O)(mu(2)-eta(2)-SCSN(C(6)H(4)))(2)](5)BF(4) (45%) and [Cp(3)Cr(3)(mu(2)-OH)(mu(3)-O)(mu(2)-eta(2)-SCN(4)Ph)(2)](9)(MeOSO(3)) (53%), together with their respective free dimethylated thiolate ligands, [MeSCSNMe(C(6)H(4))](4)BF(4) and (Me(2)SCN(4)Ph)(8)MeOSO(3). The reaction of 3 with Me(3)OBF(4) resulted in the isolation of a binuclear complex, [Cp(2)Cr(2)(mu-OH)(mu-eta(2)-SCN(4)Ph)(2)](7)BF(4) (43%), and (8)BF(4) (27%). The reaction of the thiopyridine complex, CpCr(CO)(2)(SPy) (4), with I(2) also produced a similar mu(3)-oxo complex 10 (31%), together with CpCrI(2)(THF) (11) and the disulfide (SPy)(2). Similar reactions with 2 and 3 and I(2) yielded species 5 and 7, together with 11 and disulfides derived from their respective ligands. Cyclic voltammograms recorded in solutions of 5 and 9 indicated that the compounds could be reduced and oxidized at very similar potentials. An EPR spectrum characteristic of a compound with axial symmetry was obtained for 9 at 7 K. Single-crystal X-ray diffraction analyses confirmed that species 7 is dinuclear, whereas 5 and 9 are structural trinuclear analogues, each containing a mu(3)-oxo central core.