Design and synthesis of bis-amide and hydrazide-containing derivatives of malonic acid as potential HIV-1 integrase inhibitors

Fragment-Based Design and Synthesis of Symmetrical bis-Peptidotriazoles Using Alkylidene bis-Amide Formations and Subsequent Triazole Ligation with β-Acetamido Carbonyl Scaffolds

A novel and efficient fragment-based assembly of symmetrical bis-peptidotraizoles has been developed based on double Sharpless azide-alkyne click chemistry. A new Cu(II) catalyzed protocol with a wide substrate scope was developed for accessing the symmetrical alkylidene bis-azidoamide fragment that yields the products in very good yields at room temperature without employing column purifications. The propargylated β-acetamido ketone fragment was accessed using another Cu(II) catalyzed room temperature MCR protocol. A fast double-click reaction (2 h) of symmetrical alkylidene bis-azidoamides with propargylated β-acetamido ketone fragments leads to the formation of unusual symmetrical bis-peptidotriazoles.

Visible-Light-Induced Radical Cascade Cross-Coupling via C(sp3)-H Activation and C-N/N-O Cleavage: Feasible Access to Methylenebisamide Derivatives

Here we report facile and manipulable access to methylenebisamide derivatives via visible-light-driven radical cascade processes incorporating C(sp³)-H activation and C-N/N-O cleavage. Mechanistic studies reveal that a traditional Ir-catalyzed photoredox pathway and a novel copper-induced complex-photolysis pathway are both involved, contributing to activating the inert N-methoxyamides and rendering the valuable bisamides. This approach exhibits many advantages, including mild reaction conditions, broad scope and functional group tolerance, and competitive step economy. Given the mechanistic plenitude and operational simplicity, we believe this package deal paves a promising way for the synthesis of valuable nitrogen-containing molecules.

Iridium-Catalyzed Branch-Selective Hydroalkylation of Simple Alkenes with Malonic Amides and Malonic Esters

We report the iridium-catalyzed branch-selective hydroalkylation of simple alkenes such as aliphatic alkenes and aromatic alkenes with malonic amides and malonic esters under neutral reaction conditions. A variety of aliphatic alkenes and aromatic alkenes bearing bromine, chlorine, ester, 2-thienylcarboxylate, silyl, and phthalimide groups were all found to be suitable for this hydroalkylation. The combination of this method with Krapcho dealkoxycarbonylation realized a one-pot synthesis of β-substituted amide and ester from β-amide ester and malonic ester. The hydroalkylated products derived from malonic amides are suitable for further transformation. The finely tuned reaction conditions realized the selective transformation of hydroalkylated products to 1,3-diamines or monoamides with the same reagent. Deuterium labeling experiments and measurement of the kinetic isotope effect indicated that the catalytic cycle involves a reversible step and cleavage of the C-H bond is not a rate-determining step. Density functional theory calculations provided insight into the reaction mechanism, where the carboiridation step is followed by C-H reductive elimination.

Optimized Synthesis of New N-Mustards Based on 2-Mercaptobenzoxazole Derivatives with Antitumor Activity

New di-(β-chloroethyl)-amides of some acids derived from 2-mercaptobenzoxazole were prepared by reaction of the corresponding pivalic mixed anhydrides with di-(β-chloroethyl)-amine. A study regarding the optimization of the chemical reactions was made for the case of di-(β-chloroethyl)-amines. The quantum chemical analysis by Spartan'14 was made in order to establish the most stable configuration of the ground electronic states for the obtained chemical structures and some physico-chemical parameters of N-mustards reported in this paper. Mercaptobenzoxazoles substituted in the side chain with the cytotoxic group show antitumor activity and they inhibit Ehrlich Ascites in an appreciable proportion compared to the drug I.O.B.-82, as our studies evidenced.

One-Pot Anodic Conversion of Symmetrical Bisamides of Ethylene Diamine to Unsymmetrical gem-Bisamides of Methylene Diamine

Symmetrical bisamides of ethylene diamine of type ArCONHCH₂CH₂NHCOAr undergo anodic C-C bond cleavage in acetonitrile-LiClO₄ under controlled-potential electrolysis. The electrogenerated carbocation intermediates react with the solvent acetonitrile to afford unsymmetrical gem-bisamides of type ArCONHCH₂NHCOMe in a one-pot reaction. The yields of the latter products are moderate (up to 60%). Other minor products involve two symmetrical gem-bisamides of type ArCONHCH₂NHCOAr and MeCONHCH₂NHCOMe and fragmentation products (e.g., ArCONHCHO, ArCONH₂, and ArCN).

Selectfluor-mediated oxidative methylenation of amide with N,N-dimethylpropanamide for N,N′-methylenebisamide synthesis

A simple and efficient approach for the synthesis of N,N′-methylenebisamides through a Selectfluor-mediated oxidative reaction of aromatic amides and N,N-dimethylpropanamide (DMP) is described. Remarkable results clearly reveal that DMP plays a dual role in this reaction, as both a one-carbon source and an environment-friendly solvent. Moreover, the process provides new strategies for the synthesis of bisamides with advantages of operationally simple, insensitive to atmospheric conditions, and good to high yields.

Virtual Screening and Biological Validation of Novel Influenza Virus PA Endonuclease Inhibitors

The influenza virus RNA-dependent RNA polymerase complex (RdRp), a heterotrimeric protein complex responsible for viral RNA transcription and replication, represents a primary target for antiviral drug development. One particularly attractive approach is interference with the endonucleolytic "cap-snatching" reaction by the RdRp subunit PA, more precisely by inhibiting its metal-dependent catalytic activity which resides in the N-terminal part of PA (PA-Nter). Almost all PA inhibitors (PAIs) thus far discovered bear pharmacophoric fragments with chelating motifs able to bind the bivalent metal ions in the catalytic core of PA-Nter. More recently, the availability of crystallographic structures of PA-Nter has enabled rational design of original PAIs with improved binding properties and antiviral potency. We here present a coupled pharmacophore/docking virtual screening approach that allowed us to identify PAIs with interesting inhibitory activity in a PA-Nter enzymatic assay. Moreover, antiviral activity in the low micromolar range was observed in cell-based influenza virus assays.

Crystal structure of 2-cyano-N'-(cyclo-hexyl-idene)acetohydrazide

In the title compound, C9H13N3O, the cyclo-hexyl-idene ring adopts a chair conformation and the bond-angle sum at the C atom linked to the N atom is 359.6°. The cyano-acetohydrazide grouping is close to planar (r.m.s. deviation for the non-H atoms = 0.031 Å) and subtends a dihedral angle of 64.08 (4)° with the four C atoms forming the seat of the chair. The C=O and N-H groups are in a syn conformation (O-C-N-H = -5°). In the crystal, inversion dimers linked by pairs of N-H⋯O hydrogen bonds generate R 2 (2)(8) loops; this dimer linkage is reinforced by a pair of C-H⋯O inter-actions, which generate R 2 (2)(14) loops. The dimers are linked by C-H⋯Nc (c = cyanide) inter-actions into [100] ladders, which feature C(4) chains and R 4 (4)(20) loops.

Spectroscopic and quantum mechanical investigation of N,N'-bisarylmalonamides: solvent and structural effects

The UV absorption spectra of ten N,N'-bisarylmalonamides have been recorded in the range 200-400 nm in a set of selected solvents. The solute-solvent interactions have been analyzed on the basis of the linear solvation energy relationship (LSER) concept proposed by Kamlet and Taft. The effects of substituents on the absorption spectra have been interpreted by correlating absorption frequencies with Hammett substituent constants. Furthermore, the experimental findings have been interpreted using the DFT CAM-B3LYP/6-311+G(d,p) method. Electronic energies have been calculated using the same method in combination with the implicit solvation model (conductor-like polarizable continuum model, CPCM) as well as with the explicit addition of two molecules of solvent.

Synthesis and bioactivity of 5-substituted-2-furoyl diacylhydazide derivatives with aliphatic chain

A series of 5-substituted-2-furoyl diacylhydazide derivatives with aliphatic chain were designed and synthesized. Their structures were characterized by IR, 1H NMR, elemental analysis, and X-ray single crystal diffraction. The anti-tumor bioassay revealed that some title compounds exhibited promising activity against the selected cancer cell lines, especially against the human promyelocytic leukemic cells (HL-60). Their fungicidal tests indicated that most of the title compounds showed significant anti-fungal activity. The preliminary structure-activity relationship showed that the aliphatic chain length and differences in the R2 group had obvious effects on the anti-tumor and anti-fungal activities. The bioassay results demonstrated that the title compounds hold great promise as novel lead compounds for further drug discovery.

Efficient synthesis of 4-oxo-4,5-dihydrothieno[3,2-c]quinoline-2-carboxylic acid derivatives from aniline

The first reported synthesis of potential kinase inhibitors, 4-oxo-4,5-dihydrothieno[3,2-c]quinoline-2-carboxylic acid derivatives starting from aniline is described. This efficient high yielding sequence was carried out in six steps without any chromatographic purification. A tandem nucleophilic aromatic substitution/cyclization reaction was used as a key step in the sequence. The versatile intermediate 2-carboxylic acid was used as a suitable precursor to access the functionalization of the C-ring, by convergent analog synthesis of several novel derivatives.

Mutational analysis of the binding pockets of the diketo acid inhibitor L-742,001 in the influenza virus PA endonuclease

The influenza virus PA endonuclease, which cleaves capped host pre-mRNAs to initiate synthesis of viral mRNA, is a prime target for antiviral therapy. The diketo acid compound L-742,001 was previously identified as a potent inhibitor of the influenza virus endonuclease reaction, but information on its precise binding mode to PA or potential resistance profile is limited. Computer-assisted docking of L-742,001 into the crystal structure of inhibitor-free N-terminal PA (PA-Nter) indicated a binding orientation distinct from that seen in a recent crystallographic study with L-742,001-bound PA-Nter (R. M. DuBois et al., PLoS Pathog. 8:e1002830, 2012). A comprehensive mutational analysis was performed to determine which amino acid changes within the catalytic center of PA or its surrounding hydrophobic pockets alter the antiviral sensitivity to L-742,001 in cell culture. Marked (up to 20-fold) resistance to L-742,001 was observed for the H41A, I120T, and G81F/V/T mutant forms of PA. Two- to 3-fold resistance was seen for the T20A, L42T, and V122T mutants, and the R124Q and Y130A mutants were 3-fold more sensitive to L-742,001. Several mutations situated at noncatalytic sites in PA had no or only marginal impact on the enzymatic functionality of viral ribonucleoprotein complexes reconstituted in cell culture, consistent with the less conserved nature of these PA residues. Our data provide relevant insights into the binding mode of L-742,001 in the PA endonuclease active site. In addition, we predict some potential resistance sites that should be taken into account during optimization of PA endonuclease inhibitors toward tight binding in any of the hydrophobic pockets surrounding the catalytic center of the enzyme.

Synthesis of a new group of aliphatic hydrazide derivatives and the correlations between their molecular structure and biological activity

In view of the growing demand for new compounds showing biological activity against pathogenic microorganisms, such as pathogenic and phytopathogenic fungi, the objective of this study was to synthesize a new group of aliphatic and aromatic derivatives of hydrazide. In consequence of the reactions observed during synthesis, the resulting compounds retained their linear structure. Their structure and lipophilicity, measured by high-performance liquid chromatography (HPLC), were analyzed. Correlations were determined between the compounds' molecular parameters and biological activity against Fusarium solani and Fusarium oxysporum fungi. The investigated compounds were also examined for their antifungal activity against Aspergillus fumigatus. The obtained results indicate that compounds with fluorine-containing substituents penetrate the cell structure more effectively and are characterized by higher antifungal potential than analogues with different substituents.

Microwave assisted organic synthesis (MAOS) of small molecules as potential HIV-1 integrase inhibitors

Integrase (IN) represents a clinically validated target for the development of antivirals against human immunodeficiency virus (HIV). In recent years our research group has been engaged in the stucture-function study of this enzyme and in the development of some three-dimensional pharmacophore models which have led to the identification of a large series of potent HIV-1 integrase strand-transfer inhibitors (INSTIs) bearing an indole core. To gain a better understanding of the structure-activity relationships (SARs), herein we report the design and microwave-assisted synthesis of a novel series of 1-H-benzylindole derivatives.

Synthesis, physiochemical properties, photochemical probe, and antimicrobial effects of novel norfloxacin analogues

The emerging resistance to antimicrobial drugs demands the synthesis of new remedies for microbial infections. Attempts have been made to prepare new compounds by modifications in the quinolone structure. An important method for the synthesis of new quinolone is using Vilsmeier approach but has its own limitations. The present work aimed to synthesize novel norfloxacin analogues using modified Vilsmeier approach and conduct preliminary investigations for the evaluation of their physicochemical properties, photochemical probe, and antimicrobial effects. In an effort to synthesize norfloxacin analogues, only 7-bromo-6-N-benzyl piperazinyl-4-oxoquinoline-3-carboxylic acid was isolated using Vilsmeier approach at high temperature, where N, N′-bis-(4-fluoro-3-nitrophenyl)-oxalamide and N, N′-bis-(3-chloro-4-fluorophenyl)-malonamide were obtained at low temperature. Correlation results showed that lipophilicity, molecular mass, and electronic factors might influence the activity. The synthesized compounds were evaluated for their antimicrobial effects against important pathogens, for their potential use in the inhibition of vitiligo.