Arylisothiocyanate-containing esters of caffeic acid designed as affinity ligands for HIV-1 integrase

Synthesis of N-β-brominated alkenyl isothiocyanates via dehydrogenation of alkyl isothiocyanates

This study presents a new dehydrogenative synthesis of alkenyl isothiocyanates, providing compounds with bromo and isothiocyanate groups. These reactive functionalities offer versatility for further transformations. Application in an amine sensor utilizing a coumarin-attached product demonstrates practical utility. This streamlined approach facilitates access to alkenyl isothiocyanates, valuable tools for biological studies.

Recent advancement in the synthesis of isothiocyanates

Isothiocyanates exhibit various biological characteristics, including antimicrobial, anti-inflammatory, and anticancer properties. Their significance extends to synthetic chemistry, where they serve as valuable platforms for versatile transformations. Consequently, they have attracted the attention of biologists and chemists. This review summarizes recent advancements in the synthesis of isothiocyanates. Access to a variety of starting materials is important to prepare isothiocyanates with diverse structures. This review categorizes synthetic methods into three types based on the starting materials and functional groups: (i) type A, derived from primary amines; (ii) type B, derived from other nitrogen functional groups; and (iii) type C, derived from non-nitrogen groups. Recent trends in synthetic methods have revealed the prevalence of type-A reactions derived from primary amines. However, type B reactions have rarely been reported. Notably, over the past four years, there has been a notable increase in type C reactions, indicating a growing interest in non-nitrogen-derived isothiocyanates. Overall, this review not only outlines the advancements in the synthesis of isothiocyanates but also highlights trends in the methodology.

The reaction of arylmethyl isocyanides and arylmethylamines with xanthate esters: a facile and unexpected synthesis of carbamothioates

An unexpected formation of carbamothioates by a sodium hydride-mediated reaction of arylmethyl isocyanides with xanthate esters in DMF is reported. The products thus obtained were compared with the carbamothioates obtained by the sodium hydride-mediated condensation of the corresponding benzylamines and xanthate esters in DMF. To account for these unexpected reactions, a mechanism is proposed in which the key steps are supported by quantum chemical calculations.

Characterization of Nine Compounds Isolated from the Acid Hydrolysate of Lonicera fulvotomentosa Hsu et S. C. Cheng and Evaluation of Their In Vitro Activity towards HIV Protease

In this study, we isolated nine compounds from the acid hydrolysate of the flower buds of Lonicera fulvotomentosa Hsu et S. C. Cheng and characterized their chemical structures using ¹H-NMR, ¹³C-NMR, and electron ionization mass spectroscopy (EI-MS). These compounds were identified as β-sitosterol (1), 5,5′-dibutoxy-2,2′-bifuran (2), nonacosane-10-ol (3), ethyl (3β)-3,23-dihydroxyolean-12-en-28-oate (4), oleanolic acid (5), ethyl caffeate (6), caffeic acid (7), isovanillin (8), and hederagenin (9), with 4 as a new triterpene compound. Inhibitory activity against human immunodeficiency virus (HIV) protease was also evaluated for the compounds, and only ethyl caffeate, caffeic acid, and isovanillin (6, 7, and 8) exhibited inhibitory effects, with IC₅₀ values of 1.0 μM, 1.5 μM, and 3.5 μM, respectively. Molecular docking with energy minimization and subsequent molecular dynamic (MD) simulation showed that ethyl caffeate and caffeic acid bound to the active site of HIV protease, while isovanillin drifted out from the active site and dissociated into bulk water during MD simulations, and most of the binding residues of HIV protease have been previously identified for HIV protease inhibitors. These results suggest that caffeic acid derivatives may possess inhibitory activities towards HIV protease other than previously reported inhibitory activities against HIV integrase, and thus ethyl caffeate and caffeic acid could be used as lead compounds in developing potential HIV protease inhibitors, and possibly even dual-function inhibitors against HIV.

Synthesis of Thiocarbamoyl Fluorides and Isothiocyanates Using CF3SiMe3 and Elemental Sulfur or AgSCF3 and KBr with Amines

Reactions of thiocarbonyl fluoride derived from cheap, readily available, and widely used CF₃SiMe₃, elemental sulfur, and KF with secondary amines and primary amines at room temperature in THF provided a wide variety of thiocarbamoyl fluorides and isothiocyanates in moderate to excellent yields, respectively. The two reactions show broad substrate scope and good functional group tolerance. Moreover, AgSCF₃ reacts with secondary/primary amines under KBr at room temperature, affording quantitative thiocarbamoyl fluorides/isothiocyanates, which feature late-stage application.

Organophosphine-free copper-catalyzed isothiocyanation of amines with sodium bromodifluoroacetate and sulfur

A copper-catalyzed isothiocyanation of amines with sodium bromodifluoroacetate and sulfur in the absence of organophosphine has been established. This approach represents a simple and efficient one-pot synthesis of isothiocyanates, and features excellent functional group tolerance and the use of a cheap, safe and odorless sulfur source. Moreover, this process could directly provide isothiocyanate analogous bioactive molecules, thiocarbonyl-containing pesticides and facile construction of benzoxazole and benzimidazole frames.

Caffeic Acid Esters Affect Intracellular Oxidation and Vitality of Yeast Saccharomyces cerevisiae Cells

The effect of four esters of caffeic acid, caffeic acid methanol ester (CAME), caffeic acid ethanol ester (CAEE), caffeic acid isopropyl ester (CAIPE) and caffeic acid phenethyl ester (CAPE) on intracellular oxidation, vitality and viability of the yeast Saccharomyces cerevisiae as a model eukaryotic organism was investigated. Results showed that each ester showed its own behavior at the concentrations tested. For CAPE, CAIPE and CAEE decreased intracellular oxidation and simultaneously increased cellular vitality with no changes in cellular viability compared to the control were determined. Additionally, a combination of CAIPE or CAPE with ethanolic propolis extract was observed to be more effective in decreasing intracellular oxidation compared to propolis extract alone.

Synthesis of Isothiocyanates and Unsymmetrical Thioureas with the Bench-Stable Solid Reagent (Me4N)SCF3

A highly efficient, selective, and rapid transformation of primary amines and diamines to isothiocyanates and cyclic thioureas is disclosed. As opposed to established approaches that employ toxic or volatile electrophilic liquids and require reaction control (i.e., slow addition, cooling), this protocol utilizes the bench-stable, solid reagent (Me₄N)SCF₃ at room temperature. The method is characterized by operational simplicity, high speed, efficiency, high functional group tolerance, and late-stage applicability. The byproducts are solids, allowing isolation of the target compounds by filtration.

Bioactivity and chemical synthesis of caffeic acid phenethyl ester and its derivatives

Caffeic acid phenethyl ester (CAPE), as one of the main active ingredients of the natural product propolis, shows the unique biological activities such as anti-tumor, anti-oxidation, anti-inflammatory, immune regulation, and so on. These have attracted the attention of many researchers to explore the compound with potent biological activities. This review aims to summarize its bioactivities, synthetic methods and derivatives, which will be helpful for further study and development of CAPE and its derivatives.

Computational design of a full-length model of HIV-1 integrase: modeling of new inhibitors and comparison of their calculated binding energies with those previously studied

A full-length model of integrase (IN) of the human immunodeficiency virus type 1 (HIV-1) was constructed based on the distinctly resolved X-ray crystal structures of its three domains, named N-terminal, catalytic core and C-terminal. Thirty-one already known inhibitors with varieties of structural differences as well as nine newly tested ones were docked into the catalytic core. The molecular dynamic (MD) and binding properties of these complexes were obtained by MD calculations. The binding energies calculated by molecular mechanic/Poisson Boltzmann solvation area were significantly correlationed with available IC50. Four inhibitors including two newly designed were also docked into the full-length model and their MD behaviors and binding properties were calculated. It was found that one of the newly designed compounds forms a better complex with HIV-1 IN compared to the rest including raltegravir. MD calculations were performed with AMBER suite of programs using ff99SB force field for the proteins and the general Amber force field for the ligands. In conclusion, the results have produced a promising standpoint not only in the construction of the full-length model but also in development of new drugs against it. However, the role of multimer formation and the involvement of DNAs, and their subsequent effect on the complexation and inhibition, are required to arrive at a conclusive decision.

Telore R, Sekar N. Synthesis of novel fluorescent 1,3,5-trisubstituted triazine derivatives and photophysical property evaluation of fluorophores and their BSA conjugates

Cyanuric chloride was allowed to react with

Synthesis and characterization of novel 2, 2'-bipyrimidine fluorescent derivative for protein binding

Background

Fluorescent dyes with biocompatible functional group and good fluorescence behavior are used as biosensor for monitoring different biological processes as well as detection of protein assay. All reported fluorophore used as sensors are having high selectivity and sensitivity but till there is more demand to synthesized new fluorophore which have improved fluorescence properties and good biocompatibility.

Results

Novel 4, 4'-(1, 1'-(5-(2-methoxyphenoxy)-[2, 2'-bipyrimidine]-4, 6-diyl)bis(1H-pyrazol-3, 1-diyl)) dianiline fluorescent dye was synthesized by multistep synthesis from 2-phenylacetonitrile, 2-chloropyrimidine and 2-methoxyphenol. This dye has absorption at 379 nm with intense single emission at 497 nm having fairly good quantum yield (0.375) and Stokes shift. The intermediates and dye were characterized by FT-IR, ¹H NMR, ¹³C NMR and Mass spectral analysis. The pyrazole bipyrimidine based fluorescent dye possessing two amino groups suitable for binding with protein is reported. Its utility as a biocompatible conjugate was explained by conjugation with bovine serum albumin. The method is based on direct fluorescence detection of fluorophore-labelled protein before and after conjugation. Purified fluorescent conjugate was subsequently analyzed by fluorimetry. The analysis showed that the tested conjugation reaction yielded fluorescent conjugates of the dye through carbodiimide chemistry.

Conclusion

In summery synthesized fluorophore pyrazole-bipyrimidine has very good interaction towards protein bovine serum albumin and it acts as good candidate for protein assay.

Chromone and chromanone derivatives as strand transfer inhibitors of HIV-1 integrase

HIV-1 integrase catalyzes terminal cleavage at the 3' end of the proviral DNA, removing a pair of bases and causing strand transfer by joining the 3' end to 5'-phosphates in the target DNA. Several aryl 1,3-diketo acids that can inhibit the strand transfer reaction of HIV-1 IN have been identified. Here we synthesized a new series of compounds with a chromone or chromanone ring as conformationally constrained scaffolds of 1,3-diketo acids, and then tested their ability to inhibit HIV-1 IN-mediated strand transfer. All compounds moderately inhibited HIV-1 IN activity, indicating that the conformational restriction of one keto group into a chromone or chromanone ring decreases inhibition of the HIV-1 IN strand transfer.

Caffeoylglycolic and caffeoylamino acid derivatives, halfmers of L-chicoric acid, as new HIV-1 integrase inhibitors

Human immunodeficiency virus (HIV) integrase (IN) catalyzes the integration of HIV DNA copy into the host cell DNA. L-Chicoric acid (1) has been found to be one of the most potent HIV-1 integrase inhibitor. Caffeoylglycolic and caffeoylamino acid derivatives' halfmeric structures of L-chicoric acid 2 were synthesized for the purpose of simplifying the structure of L-chicoric acid. Among synthesized, compounds 2c and 3f showed HIV-1 IN inhibitory activities with IC(50) values of 10.5 and 12.0 microM, respectively, comparable to that of parent compound L-chicoric acid (IC(50)=15.7 microM).

Arylisothiocyanato selective androgen receptor modulators (SARMs) for prostate cancer

A new series of androgen receptor targeted agents (ARTA) was prepared and tested in androgen-dependent and -independent prostate cancer cell lines. These agents were bicalutamide analogs with isothiocyanato substituted B-rings. Also, the linker sulfone of R-bicalutamide was maintained or replaced with several alternative linkages including ether, amine, N-methylamine, thioether, and methylene (in this case the product was a racemic mixture) functional groups at the X-position. To expand the structure-activity relationship (SAR) of these arylisothiocyanato AR ligands, B-ring halogenated arylisothiocyanato ligands were also prepared and tested. The arylisothiocyanato AR ligands showed strong binding affinities to AR ranging from 0.6 to 54 nM. Among them, thioether and ether linkages demonstrated high binding affinities (0.6 and 4.6 nM, respectively) and selective cell growth inhibition (approximately 3- to 6-fold) for LNCaP, an androgen-dependent prostate cancer cell line, when compared to the androgen independent prostate cell lines (DU145, PC-3, and PPC-1) and a bladder cell line (TSU-Pr1). However, the ligands were inactive (IC50>100 mM) in a normal monkey kidney cell line (CV-1) that was used as the control for non-specific toxicity.

Synthesis and spectroscopic characterisation of new ESIPT fluorescent protein probes

Three new benzazole isothiocyanate fluorescent dyes, 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzoxazole, 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzothiazole and 2-(4'-isothiocyanate-2'-hydroxyphenyl)benzimidazole were synthesised, purified until optical purity grade and characterised by spectroscopic techniques. UV/VIS and steady-state fluorescence were also applied to characterise the photophysical behaviour of the dyes. These dyes exhibit an intense fluorescence emission with a large Stokes shift, inherent to the class of benzazoles which relax by the excited state intramolecular proton transfer (ESIPT) mechanism. The dyes were studied for labeling bovine serum albumin (BSA), resulting conjugates BSA-dye with a remarkable photostability under UV/VIS radiation in relation to classical protein labels. The resulting conjugates presented fluorescence in the blue-green region. Direct fluorescence detection of protein-labeled with those dyes after polyacrylamide gel electrophoresis indicates their potential use as fluorescent probes for proteins.

Mass spectrometric analysis of the HIV-1 integrase-pyridoxal 5'-phosphate complex reveals a new binding site for a nucleotide inhibitor

HIV-1 integrase (IN) is an important target for designing new antiviral therapies. Screening of potential inhibitors using recombinant IN-based assays has revealed a number of promising leads including nucleotide analogs such as pyridoxal 5'-phosphate (PLP). Certain PLP derivatives were shown to also exhibit antiviral activities in cell-based assays. To identify an inhibitory binding site of PLP to IN, we used the intrinsic chemical property of this compound to form a Schiff base with a primary amine in the protein at the nucleotide binding site. The amino acid affected was then revealed by mass spectrometric analysis of the proteolytic peptide fragments of IN. We found that an IC(50) concentration (15 mum) of PLP modified a single IN residue, Lys(244), located in the C-terminal domain. In fact, we observed a correlation between interaction of PLP with Lys(244) and the compound's ability to impair formation of the IN.DNA complex. Site-directed mutagenesis studies confirmed an essential role of Lys(244) for catalytic activities of recombinant IN and viral replication. Molecular modeling revealed that Lys(244) together with several other DNA binding residues provides a plausible pocket for a nucleotide inhibitor-binding site. To our knowledge, this is the first report indicating that a small molecule inhibitor can impair IN activity through its binding to the protein C terminus. At the same time, our findings highlight the importance of structural analysis of the full-length protein.

Design and synthesis of novel dihydroxyindole-2-carboxylic acids as HIV-1 integrase inhibitors

In a search for new HIV-1 integrase (IN) inhibitors, we synthesized and evaluated the biological activity of 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and a series of its derivatives. These compounds were designed as conformationally constrained analogues of the acrylate moiety of caffeic acid phenethyl ester (CAPE). DHICA, an intermediate in the biosynthesis of melanins, was prepared as a monomeric unit by a novel synthetic route. In order to perform coherent SAR studies, two series of DHICA amides were synthesized. First, to validate the utility of a previously identified three-point pharmacophore based on CAPE in inhibitor design, we prepared a series of benzyl- or phenylethylamine substituted derivatives lacking and containing hydroxyl groups. Second, dimers of DHICA containing various aminoalkylamine linkers were also prepared with a goal to increase potency. All compounds were tested against purified IN and the C65S mutant in enzyme-based assays. They were also tested for cytotoxicity in an ovarian carcinoma cell line and antiviral activity in HIV-1-infected CEM cells. Seven compounds inhibited catalytic activities of purified IN with IC50 values below 10 microM. Further computational docking studies were performed to determine the title compounds' mode of interaction with the IN active site. The residues K156, K159 and D64 were the most important for potency against purified IN.

An Approach towards the Quantitative Structure-Activity Relationships of Caffeic Acid and its Derivatives

Caffeic acid and its derivatives are already known to possess a wide range of biological activities. We have developed quantitative structure-activity relationships (QSARs) for different series of caffeic acid derivatives (including caffeic acid) in order to understand the chemical-biological interactions governing antitumor activity against six different tumor cell lines, nitric oxide production, anti-HIV and enzymatic activities, and binding affinity to the lck domain. QSAR results have shown that the different activities of caffeic acid and its derivatives are largely dependent on their hydrophobicity or molar refractivity, with a bilinear correlation being the most important.

Synthesis, antiviral, and anti-HIV-1 integrase activities of 3-aroyl-1,1-dioxo-1,4,2-benzodithiazines

HIV-1 integrase (IN) is an essential enzyme for effective viral replication and is an attractive target for selective blockade of viral infection. Previously, we identified a series of sulfones, sulfonamides, and mercaptosalicylhydrazides (MBSAs) as IN inhibitors with antiviral activities in cell-based assays. In an effort to optimize a series of our active site directed lead compounds, we designed and synthesized novel benzodithiazines starting from MBSAs. In contrast to all reported IN inhibitors benzodithiazines are essentially nontoxic. Significant antiviral potency was only observed at concentration exceedingly higher than that required to inhibit purified IN.

Identification of an inhibitor-binding site to HIV-1 integrase with affinity acetylation and mass spectrometry

We report a methodology that combines affinity acetylation with MS analysis for accurate mapping of an inhibitor-binding site to a target protein. For this purpose, we used a known HIV-1 integrase inhibitor containing aryl di-O-acetyl groups (Acetylated-Inhibitor). In addition, we designed a control compound (Acetylated-Control) that also contained an aryl di-O-acetyl group but did not inhibit HIV-1 integrase. Examination of the reactivity of these compounds with a model peptide library, which collectively contained all 20 natural amino acids, revealed that aryl di-O-acetyl compounds effectively acetylate Cys, Lys, and Tyr residues. Acetylated-Inhibitor and Acetylated-Control exhibited comparable chemical reactivity with respect to these small peptides. However, these two compounds differed markedly in their interactions with HIV-1 integrase. In particular, Acetylated-Inhibitor specifically acetylated K173 at its inhibitory concentration (3 microM) whereas this site remained unrecognized by Acetylated-Control. Our data enabled creation of a detailed model for the integrase:Acetylated-Inhibitor complex, which indicated that the inhibitor selectively binds at an architecturally critical region of the protein. The methodology reported herein has a generic application for systems involving a variety of ligand-protein interactions.

Catechol-Substituted l -Chicoric acid analogues as HIV integrase inhibitors

HIV integrase catalyzes the integration of HIV DNA copy into the host cell DNA, which is essential for the production of progeny viruses. L-Chicoric acid and dicaffeoylquinic acids, isolated from plants, are well known potent inhibitors of HIV integrase. The common structural features of these inhibitors are caffeic acid derivatives connected to tartaric acid or quinic acid through ester bonds. In the present study, we have synthesized and tested the inhibitory activities of a new type of HIV IN inhibitors, which has catechol groups in place of caffeoyl groups in the structure of L-chicoric acid. Upon substitution of catechol groups at succinic acid, pyrrole-dicarboxylic acid, maleimide or maleic anhydride, the inhibitory activities (IC(50)=3.8-23.6 microM) were retained or remarkably increased when compared to parent compound L-chicoric acid (IC(50)=13.7 microM).

Caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors

HIV-1 integrase (IN) is an essential enzyme for retroviral replication and a rational target for the design of anti-AIDS drugs. In the present study, we have designed, synthesized and tested a series of caffeoyl naphthalenesulfonamide derivatives as HIV integrase inhibitors. Among these compounds, we found that HIV integrase inhibitory activities of compounds III-3 and III-4 were more potent than L-chicoric acid (IC(50)=11.8 microg/mL) and others were comparable to L-chicoric acid. Furthermore, the structure-activity relationships of these compounds were studied. The information gathered from this paper will be useful in the development and design of HIV-1 integrase inhibitors in the future.