Two approaches to the use of benzo[c][1,2]oxaboroles as active fragments for synthetic transformation of clarithromycin.

Clarithromycin (active against Gram positive infections) and 1-hydroxy-1,3-dihydrobenzo[c][1,2]oxaborole derivatives (effective for Gram negative microbes) are the ligands of bacterial RNA. The antimicrobial activities of these benzoxaboroles linked with clarithromycin at 9 or 4″ position were compared. Two synthetic pathways for these conjugates were elaborated. First pathway explored the substitution of the C-9 carbonyl group of macrolactone's cycle via oxime linker, the second direction used the modification of the 4″-O-group of cladinose via the formation of carbamates of benzoxaboroles. 4″-O-(3-S-(1-Hydroxy-1,3-dihydro-benzo[c][1,2]oxaborole)-methyl-carbamoyl-clarithromycin showed twofold decrease in MICs for S. epidermidis and S. pneumoniae than clarithromycin. 4″-O-Modified clarithromycin demonstrated an efficacy against Gram positive strains only. Compounds with C-9 substitution were more active than 4″-O-substituted antibiotics for susceptible strains E. coli tolC and did not exceed the activity of initial antibiotics.

Structure-antifungal activity relationships of polyene antibiotics of the amphotericin B group.

A comprehensive comparative analysis of the structure-antifungal activity relationships for the series of biosynthetically engineered nystatin analogues and their novel semisynthetic derivatives, as well as amphotericin B (AMB) and its semisynthetic derivatives, was performed. The data obtained revealed the significant influence of the structure of the C-7 to C-10 polyol region on the antifungal activity of these polyene antibiotics. Comparison of positions of hydroxyl groups in the antibiotics and in vitro antifungal activity data showed that the most active are the compounds in which hydroxyl groups are in positions C-8 and C-9 or positions C-7 and C-10. Antibiotics with OH groups at both C-7 and C-9 had the lowest activity. The replacement of the C-16 carboxyl with methyl group did not significantly affect the in vitro antifungal activity of antibiotics without modifications at the amino group of mycosamine. In contrast, the activity of the N-modified derivatives was modulated both by the presence of CH3 or COOH group in the position C-16 and by the structure of the modifying substituent. The most active compounds were tested in vivo to determine the maximum tolerated doses and antifungal activity on the model of candidosis sepsis in leukopenic mice (cyclophosphamide-induced). Study of our library of semisynthetic polyene antibiotics led to the discovery of compounds, namely, N-(L-lysyl)-BSG005 (compound 3n) and, especially, L-glutamate of 2-(N,N-dimethylamino)ethyl amide of S44HP (compound 2j), with high antifungal activity that were comparable in in vitro and in vivo tests to AMB and that have better toxicological properties.

Synthesis and cytotoxicity of oligomycin A derivatives modified in the side chain.

A novel way of chemical modification of the macrolide antibiotic oligomycin A (1) at the side chain was developed. Mesylation of 1 with methane sulfonyl chloride in the presence of 4-dimethylaminopyridine produced 33-O-mesyl oligomycin in 56% yield. Reactions of this intermediate with sodium azide produced the key derivative 33-azido-33-deoxy-oligomycin A in 60% yield. 1,3-Dipolar cycloaddition reaction with propiolic acid, methyl ester of propiolic acid, and phenyl acetylene resulted in 33-deoxy-33-(1,2,3-triazol-1-yl)oligomycin A derivatives substituted at N4 of the triazole cycle. The mesylated oligomycin A and 33-deoxy-33-azidooligomycin A did not inhibit F0F1 ATFase ATPase; however, 33-azido-33-deoxy-oligomycin A and the derivatives containing 4-phenyltriazole, 4-methoxycarbonyl-triazole and 3-dimethylaminoethyl amide of carboxyltriazole substituents demonstrated a high cytotoxicity against K562 leukemia and HCT116 human colon carcinoma cell lines whereas non-malignant skin fibroblasts were less sensitive to these compounds. Novel series of oligomycin A derivatives allow for the search of intracellular molecules beyond F0F1 ATP synthase relevant to the cytotoxic properties of this perspective chemical class.

Target protein interactions of indole-3-carbinol and the highly potent derivative 1-benzyl-I3C with the C-terminal domain of human elastase uncouples cell cycle arrest from apoptotic signaling.

Elastase is the only currently identified target protein for indole-3-carbinol (I3C), a naturally occurring hydrolysis product of glucobrassicin in cruciferous vegetables such as broccoli, cabbage, and Brussels sprouts that induces a cell cycle arrest and apoptosis of human breast cancer cells. In vitro elastase enzymatic assays demonstrated that I3C and at lower concentrations its more potent derivative 1-benzyl-indole-3-carbinol (1-benzyl-I3C) act as non-competitive allosteric inhibitors of elastase activity. Consistent with these results, in silico computational simulations have revealed the first predicted interactions of I3C and 1-benzyl-I3C with the crystal structure of human neutrophil elastase, and identified a potential binding cluster on an external surface of the protease outside of the catalytic site that implicates elastase as a target protein for both indolecarbinol compounds. The Δ205 carboxyterminal truncation of elastase, which disrupts the predicted indolecarbinol binding site, is enzymatically active and generates a novel I3C resistant enzyme. Expression of the wild type and Δ205 elastase in MDA-MB-231 human breast cancer cells demonstrated that the carboxyterminal domain of elastase is required for the I3C and 1-benzyl-I3C inhibition of enzymatic activity, accumulation of the unprocessed form of the CD40 elastase substrate (a tumor necrosis factor receptor family member), disruption of NFκB nuclear localization and transcriptional activity, and induction of a G1 cell cycle arrest. Surprisingly, expression of the Δ205 elastase molecule failed to reverse indolecarbinol stimulated apoptosis, establishing an elastase-dependent bifurcation point in anti-proliferative signaling that uncouples the cell cycle and apoptotic responses in human breast cancer cells.

Inhibition of hepatitis C virus replication by semi-synthetic derivatives of glycopeptide antibiotics.

OBJECTIVES: Some semi-synthetic derivatives of glycopeptide antibiotics have been shown to exert in vitro antiviral activity against HIV and coronaviruses. Here we report and characterize the in vitro anti-hepatitis C virus (HCV) activity of several semi-synthetic derivatives of teicoplanin aglycone. METHODS: Anti-HCV activity was analysed in: (i) three different subgenomic HCV replicon systems using a luciferase or quantitative RT-PCR (qRT-PCR) assay; and (ii) an infectious HCV cell culture system by means of qRT-PCR and immunofluorescence assays. RESULTS: Several teicoplanin aglycone derivatives elicited selective anti-HCV activity in replicons as well as infectious cell culture systems, with LCTA-949 being the most potent derivative. LCTA-949 proved, in contrast to several directly acting antivirals for HCV, efficient in clearing cells of their replicons. When LCTA-949 was combined with HCV protease or polymerase inhibitors an overall additive effect was observed. Likewise, LCTA-949 was equipotent against wild-type replicons as well as against replicons resistant to polymerase and protease inhibitors. Following up to 4 months of selective pressure, no drug-resistant replicons were selected. When combined with the HCV NS3 protease inhibitor VX-950, LCTA-949 prevented the development of VX-950-resistant variants. CONCLUSIONS: Semi-synthetic derivatives of teicoplanin aglycone constitute a novel class of HCV replication inhibitors that are not cross-resistant with various HCV protease and polymerase inhibitors and in particular are potent in clearing hepatoma cells of their replicons. This class of molecules also provides a good tool to obtain novel insights into the replication cycle of HCV and into cellular factors/processes that are crucial for viral replication.

Modification of olivomycin A at the side chain of the aglycon yields the derivative with perspective antitumor characteristics.

A novel way of chemical modification of the antibiotic olivomycin A (1) at the side chain of the aglycon moiety was developed. Interaction of olivomycin A with the sodium periodate produced the key acid derivative olivomycin SA (2) in 86% yield. This acid was used in the reactions with different amines in the presence of benzotriazol-1-yl-oxy-trispyrrolidino-phosphonium hexafluorophosphate (PyBOP) or diphenylphosphoryl azide (DPPA) to give corresponding amides. Whereas olivomycin SA was two orders of magnitude less cytotoxic than the parent antibiotic, the amides of 2 demonstrated a higher cytotoxicity. In particular, N,N-dimethylaminoethylamide of olivomycin SA showed a pronounced antitumor effect against transplanted experimental lymphoma and melanoma and a remarkably high binding constant to double stranded DNA. The therapeutic effects of this derivative were achievable at tolerable concentrations, suggesting that modifications of the aglycon's side chain, namely, its shortening to methoxyacetic residue and blocking of free carboxyl group, are straightforward for the design of therapeutically applicable derivatives of olivomycin A.

Synthesis and cytotoxic potency of novel tris(1-alkylindol-3-yl)methylium salts: role of N-alkyl substituents.

Novel derivatives of tris(indol-3-yl)methane and tris(indol-3-yl)methylium salts with the alkyl substituents at the N-atoms of the indole rings were synthesized. An easy substitution of indole rings in trisindolylmethanes for other indoles under the action of acids is demonstrated, and the mechanism of substitution is discussed. To obtain trisindolylmethylium salts, the environmentally safe method of oxidation of trisindolylmethanes with air oxygen in acidic conditions was developed. Tris(1-alkylindol-3-yl)methanes and tris(1-alkylindol-3-yl)methylium salts represent three-bladed molecular propellers whose physico-chemical and biological properties strongly depend on the N-alkyl substituent. The cytotoxicity of novel compounds increased with the number of C atoms in the alkyl chains, with optimal number n=3-5 whereas the derivatives with longer side chains were less cytotoxic. The most potent novel compounds killed human tumor cells at nanomolar-to-submicromolar concentrations, being one order of magnitude more potent than the prototype antibiotic turbomycin A [tris(indol-3-yl)methylium salt]. Apoptosis in HCT116 colon carcinoma cell line induced by tris(1-pentyl-1H-indol-3-yl)methylium methanesulfonate was detectable at concentrations tolerable by normal blood lymphocytes. Thus, N-alkyl substituted tris(1-alkylindol-3-yl)methylium salts emerge as perspective anticancer drug candidates.

Reaction of the antitumor antibiotic olivomycin I with aryl diazonium salts. Synthesis, cytotoxic and antiretroviral potency of 5-aryldiazenyl-6-O-deglycosyl derivatives of olivomycin I.

The azo coupling of the antibiotic olivomycin I (1) with aryl diazonium tetrafluoroborates produced 5-aryldiazenyl-6-O-deglycosyl derivatives of 1. The structures of new compounds were confirmed by (1)H NMR and mass spectrometry analysis. A quantum-chemical study was performed to analyze the possible directions of electrophilic substitution of 1 and the easiness of 6-O-disaccharide hydrolysis in the course of azo coupling. The antiproliferative and anti-retroviral activities of novel derivatives were studied.

Synthesis and cytotoxic properties of 4,11-bis[(aminoethyl)amino]anthra[2,3-b]thiophene-5,10-diones, novel analogues of antitumor anthracene-9,10-diones.

We developed the synthesis of a series of thiophene-fused tetracyclic analogues of the antitumor drug ametantrone. The reactions included nucleophilic substitution of methoxy groups in 4,11-dimethoxyanthra[2,3-b]thiophene-5,10-diones with ethylenediamines, producing the derivatives of 4,11-diaminoanthra[2,3-b]thiophene-5,10-dione in good yields. Several compounds showed marked antiproliferative potency against doxorubicin-selected, P-glycoprotein-expressing tumor cells and p53(-/-) cells. The cytotoxicity of some novel compounds for P-glycoprotein-positive cells is highly dependent on N-substituent at the terminal amino group of ethylenediamine moiety. The cytotoxic potency of selected compounds correlated with their ability to attenuate the functions of topoisomerase I and telomerase, strongly suggesting that these enzymes are the major targets of antitumor activity of anthra[2,3-b]thiophene-5,10-dione derivatives.

N-Alkoxy derivatization of indole-3-carbinol increases the efficacy of the G1 cell cycle arrest and of I3C-specific regulation of cell cycle gene transcription and activity in human breast cancer cells.

Indole-3-carbinol (I3C), a naturally occurring component of Brassica vegetables, such as cabbage, broccoli, and Brussels sprouts, induces a G1 cell cycle arrest of human breast cancer cells. Structure-activity relationships of I3C that mediate this anti-proliferative response were investigated using synthetic and natural I3C derivatives that contain substitutions at the indole nitrogen. Nitrogen substitutions included N-alkoxy substituents of one to four carbons in length, which inhibit dehydration and the formation of the reactive indolenine. Analysis of growth and cell cycle arrest of indole-treated human breast cancer cells revealed a striking increase in efficacy of the N-alkoxy I3C derivatives that is significantly enhanced by the presence of increasing carbon lengths of the N-alkoxy substituents. Compared to I3C, the half maximal growth arrest responses occurred at 23-fold lower indole concentration for N-methoxy I3C, 50-fold lower concentration for N-ethoxy I3C, 217-fold lower concentration for N-propoxy I3C, and 470-fold lower concentration for N-butoxy I3C. At these lower concentrations, each of the N-alkoxy substituted compounds induced the characteristic I3C response in that CDK6 gene expression, CDK6 promoter activity, and CDK2 specific enzymatic activity for its retinoblastoma protein substrate were strongly down-regulated. 3-Methoxymethylindole and 3-ethoxymethylindole were approximately as bioactive as I3C, whereas both tryptophol and melatonin failed to induce the cell cycle arrest, showing the importance of the C-3 hydroxy methyl substituent on the indole ring. Taken together, our study establishes the first I3C structure-activity relationship for cytostatic activities, and implicates I3C-based N-alkoxy derivatives as a novel class of potentially more potent experimental therapeutics for breast cancer.

Eremomycin pyrrolidide: a novel semisynthetic glycopeptide with improved chemotherapeutic properties.

PURPOSE: Development of new semisynthetic glycopeptides with improved antibacterial efficacy and reduced pseudoallergic reactions. METHODS: Semisynthetic glycopeptides 3-6 were synthesized from vancomycin (1) or eremomycin (2) by the condensation with pyrrolidine or piperidine. The minimum inhibitory concentration (MIC) for the new derivatives was measured by the broth micro-dilution method on a panel of clinical isolates of Staphylococcus and Enterococcus. Acute toxicity (50% lethal dose, maximum tolerated doses), antibacterial efficacy on model of systemic bacterial infection with S. aureus and pseudoallergic inflammatory reaction (on concanavalin A) of eremomycin pyrrolidide (5) were evaluated in mice according to standard procedures. RESULTS: The eremomycin pyrrolidide (5) was the most active compound and showed a high activity against Gram-positive bacteria: vancomycin-susceptible staphylococci and enterococci (minimum inhibitory concentrations [MICs] 0.13-0.25 mg/L), as well as vancomycin-intermediate resistant Staphylococcus aureus (MICs 1 mg/L). Antimicrobial susceptibility tested on a panel of 676 isolates showed that 5 had similar activity for the genera Staphylococcus and Enterococcus with MIC90=0.5 mg/L, while vancomycin had MIC90=1-2 mg/L. The number of resistant strains of Enterococcus faecium (vancomycin-resistant enterococci) (MIC =64 mg/L) with this value was 7 (8%) for vancomycin (1) and 0 for the compound 5. In vivo comparative studies in a mouse model of systemic bacterial infection with S. aureus demonstrated that the efficacy of 5 was notably higher than that of the original antibiotics 1 and 2. In contrast to 1, compound 5 did not induce pseudoallergic inflammatory reaction (on concanavalin A). CONCLUSION: The new semisynthetic derivative eremomycin pyrrolidide (5) has high activity against staphylococci and enterococci including vancomycin-resistant strains. Compound 5 has a higher efficacy in a model of staphylococcal sepsis than vancomycin (1) or eremomycin (2). In striking contrast to natural antibiotics, the novel derivative 5 does not induce a pseudoallergic inflammatory reaction to concanavalin A and therefore has no histamine release activity. These results indicate the advantages of a new semisynthetic glycopeptide antibiotic eremomycin pyrrolidide (5) which may be a prospective antimicrobial agent for further pre-clinical and clinical evaluations.

Novel semisynthetic derivative of antibiotic Eremomycin active against drug-resistant gram-positive pathogens including Bacillus anthracis.

Five adamantyl-containing carboxamides of eremomycin or vancomycin were synthesized and their antibacterial activities against some Gram-positive clinical isolates were investigated in vitro and in vivo. The adamantyl-2 amide of glycopeptide antibiotic eremomycin (1a in Chart 1, AN0900) was the most active compound and showed high activity against several Gram-positive pathogens: vancomycin-susceptible staphylococci and enterococci, glycopeptide-intermediate-resistant Staphylococcus aureus, and glycopeptide-resistant enterococci. Compound 1a was equally active in vitro against both Ciprofloxacin-susceptible and -resistant Bacillus anthracis strains (MICs 0.25-0.5 microg/mL). It was distinguished by having a 2.8 h half-life (t1/2) in mice and a volume of distribution of 2.18 L/kg. Compound 1a was active against Staphylococcus aureus in mice (iv) and provided complete protection against a lethal intravenous challenge with vegetative B. anthracis bacilli and also in a murine pulmonary anthrax model in which mice were challenged with Bacillus anthracis spores.

N'-(alpha-aminoacyl)- and N'-alpha-(N(alpha)-alkylamino)acyl derivatives of vancomycin and eremomycin. I. Synthesis of N'-(alpha-aminoacyl)- and N'-alpha-(N(alpha)-alkylamino)acyl derivatives of vancomycin and eremomycin by selective aminoacylation of the amino sugar of the disaccharide branch.

The acylation of unprotected vancomycin or eremomycin with activated esters of N(alpha)-protected amino acids or N(alpha)-alkyl-N(alpha)-Fmoc-amino acids is directed selectively to the amino group of the disaccharide branch (N') and after Fmoc-group removal leads to the corresponding N'-alpha-aminoacyl derivatives. A series of N'-alpha-aminoacyl and N'-alpha-(N(alpha)-alkylamino)acyl derivatives of eremomycin and vancomycin containing hydrophobic moieties has been synthesized. The structures of all derivatives were confirmed by Electrospray Ionization mass-spectral (ESI MS) analysis, and by chemical degradation methods. Position of the introduced N'-alpha-aminoacyl- and N-(N(alpha)-alkylamino)acyl groups were determined after Edman degradation and acidic hydrolysis. The structures of the synthesized starting reagents (N(alpha)-alkylamino acids or N(alpha)-alkyl-N(alpha)-Fmocamino acids) were confirmed by NMR-spectra data. In general, N'-(N-alkylglycyl)-derivatives were more active than the corresponding N'-alpha-(N(alpha)-alkylamino)acylated derivatives containing other amino acids (L-Lys, L-Met, L-Orn, L- and D-Ala, L- and D-Phe and benzyl-O-L-Tyr).

N'-(alpha-aminoacyl)- and N'-alpha-(N-alkylamino)acyl derivatives of vancomycin and eremomycin. II. Antibacterial activity of N'-(alpha-aminoacyl)- and N'-alpha-(N-alkylamino)acyl derivatives of vancomycin and eremomycin.

The antibacterial activities of the series of novel N'-(alpha-aminoacyl)- and N'-alpha-(N-akylamino)acyl derivatives of eremomycin and vancomycin containing hydrophobic moieties have been investigated. The N'-(N-alkylglycyl) derivatives of vancomycin are more active against vancomycin-susceptible staphylococci and enterococci and glycopeptide intermediate-resistant Staphylococcus aureus (GISA) than the corresponding eremomycin derivatives, but except for N'-[N-(p-octyloxybenzyl)glycyl-vancomycin] (28) and N'-[N-(p-octyloxybenzyl)-L-alanyl-vancomycin (33)--they are less active against glycopeptide-resistant enterococci (GRE). Derivatives 28 and 33 are the most active compounds (MIC's for glycopeptide-sensitive staphylococci and enterococci are 0.25 approximately 1 microg/ml, for GISA 1 approximately 2 microg/ml, for GRE 2 approximately 6 microg/ml). In in vivo studies, derivative 28 was active against S. aureus infections in mice with ED(50) 1 mg/kg versus 2 mg/kg for vancomycin (iv). In general N'-(N-alkylglycyl)-derivatives of vancomycin and eremomycin were more active than the corresponding N'-aminoacylated derivatives of these antibiotics containing other than glycin amino acids (L-Lys, L-Met, L-Orn, L- and D-Ala) and also L- and D-Phe or benzyl-O-L-Tyr.

Indole-3-carbinol (I3C) analogues are potent small molecule inhibitors of NEDD4-1 ubiquitin ligase activity that disrupt proliferation of human melanoma cells.

The HECT domain-containing E3 ubiquitin ligase NEDD4-1 (Neural precursor cell Expressed Developmentally Down regulated gene 4-1) is frequently overexpressed in human cancers and displays oncogenic-like properties through the ubiquitin-dependent regulation of multiple protein substrates. However, little is known about small molecule enzymatic inhibitors of HECT domain-containing ubiquitin ligases. We now demonstrate that indole-3-carbinol (I3C), a natural anti-cancer phytochemical derived from cruciferous vegetables such as cabbage and broccoli, represents a new chemical scaffold of small molecule enzymatic inhibitors of NEDD4-1. Using in vitro ubiquitination assays, I3C, its stable synthetic derivative 1-benzyl-I3C and five novel synthetic analogues were shown to directly inhibit NEDD4-1 ubiquitination activity. Compared to I3C, which has an IC50 of 284µM, 1-benzyl-I3C was a significantly more potent NEDD4-1 enzymatic inhibitor with an IC50 of 12.3µM. Compounds 2242 and 2243, the two indolecarbinol analogues with added methyl groups that results in a more nucleophilic benzene ring π system, further enhanced potency with IC50s of 2.71µM and 7.59µM, respectively. Protein thermal shift assays that assess small ligand binding, in combination with in silico binding simulations with the crystallographic structure of NEDD4-1, showed that each of the indolecarbinol compounds bind to the purified catalytic HECT domain of NEDD4-1. The indolecarbinol compounds inhibited human melanoma cell proliferation in a manner that generally correlated with their effectiveness as NEDD4-1 enzymatic inhibitors. Taken together, we propose that I3C analogues represent a novel set of anti-cancer compounds for treatment of human melanomas and other cancers that express indolecarbinol-sensitive target enzymes.

Polycyclic peptide and glycopeptide antibiotics and their derivatives as inhibitors of HIV entry.

Antiviral activity and other biological properties of two groups of polycyclic peptides are discussed. Antibiotics of the complestatin-kistamycin group have a structural motif similar to that of the peptide core of antibacterial antibiotics of the vancomycin-teicoplanin group though no amino acid component in the chloropeptin-kistamicin antibiotics is identical to an amino acid incorporated in the peptide core of the antibiotics of the vancomycin-teicoplanin group. Chloropeptins and the hydrophobic several derivatives of antibacterial antibiotics are inhibitors of HIV and some other viruses. They interfere with the viral (i.e. HIV) entry process. Chemical modifications of natural glycopeptide antibiotics led to the compounds with antiviral properties whereas antibacterial properties were lost. These glycopeptide aglycons derivatives can be envisaged as potential lead compounds for application as microbicides against sexual HIV transmission.

Inhibition of feline (FIPV) and human (SARS) coronavirus by semisynthetic derivatives of glycopeptide antibiotics.

Various semisynthetic derivatives of glycopeptide antibiotics including vancomycin, eremomycin, teicoplanin, ristocetin A and DA-40926 have been evaluated for their inhibitory activity against feline infectious peritonitis virus (FIPV) and human (SARS-CoV, Frankfurt-1 strain) coronavirus in cell culture in comparison with their activity against human immunodeficiency virus (HIV). Several glycopeptide derivatives modified with hydrophobic substituents showed selective antiviral activity. For the most active compounds, the 50% effective concentrations (EC(50)) were in the lower micromolar range. In general, removal of the carbohydrate parts of the molecules did not affect the antiviral activity of the compounds. Some compounds showed inhibitory activity against both, whereas other compounds proved inhibitory to either, FIPV or SARS-CoV. There was no close correlation between the EC(50) values of the glycopeptide derivatives for FIPV or SARS-CoV.

Quantitative parameters of complexes of tris(1-alkylindol-3-yl)methylium salts with serum albumin: Relevance for the design of drug candidates.

Triarylmethane derivatives are extensively investigated as antitumor and antibacterial drug candidates alone and as photoactivatable compounds. In the series of tris(1-alkylindol-3-yl)methylium salts (TIMs) these two activities differed depending on the length of N-alkyl chain, with C4-5 derivatives being the most potent compared to the shorter or longer chain analogs and to the natural compound turbomycin A (no N-substituent). Given that the human serum albumin (HSA) is a major transporter protein with which TIMs can form stable complexes, and that the formation of these complexes might be advantageous for phototoxicity of TIMs we determined the quantitative parameters of TIMs-HSA binding using spectroscopic methods and molecular docking. TIMs bound to HSA (1:1 stoichiometry) altered the protein's secondary structure by changing the α-helix/ß-turn ratio. The IIa subdomain (Sudlow site I) is the preferred TIM binding site in HSA as determined in competition experiments with reference drugs ibuprofen and warfarin. The values of binding constants increased with the number of CH2 groups from 0 to 6 and then dropped down for C10 compound, a dependence similar to the one observed for cytocidal potency of TIMs. We tend to attribute this non-linear dependence to an interplay between hydrophobicity and steric hindrance, the two key characteristics of TIMs-HSA complexes calculated in the molecular docking procedure. These structure-activity relationships provide evidence for rational design of TIMs-based antitumor and antimicrobial drugs.

Discovery of antitumor anthra[2,3-b]furan-3-carboxamides: Optimization of synthesis and evaluation of antitumor properties.

Anthraquinones and their analogues, in particular heteroarene-fused anthracendiones, are prospective scaffolds for new compounds with improved antitumor characteristics. We herein report the use of a 'scaffold hopping' approach for the replacement of the core structure in the previously discovered hit compound naphtho[2,3-f]indole-5,10-dione 2 with an alternative anthra[2,3-b]furan-5,10-dione scaffold. Among 13 newly synthesized derivatives the majority of 4,11-dihydroxy-2-methyl-5,10-dioxoanthra[2,3-b]furan-3-carboxamides demonstrated a high antiproliferative potency against a panel of wild type and drug resistant tumor cell lines, a property superior over the reference drug doxorubicin or lead naphtho[2,3-f]indole-5,10-dione 2. At low micromolar concentrations the selected derivative of (R)-3-aminopyrrolidine 3c and its stereoisomer (S)-3-aminopyrrolidine 3d caused an apoptotic cell death preceded by an arrest in the G2/M phase. Studies of intracellular targets showed that 3c and 3d formed stable intercalative complexes with the duplex DNA as determined by spectral analysis and molecular docking. Both 3c and 3d attenuated topoisomerase 1 and 2 mediated unwinding of the supercoiled DNA via a mechanism different from conventional DNA-enzyme tertiary complex formation. Furthermore, 3d decreased the activity of selected human protein kinases in vitro, indicating multiple targeting by the new chemotype. Finally, 3d demonstrated an antitumor activity in a model of murine intraperitoneally transplanted P388 leukemia, achieving the increase of animal life span up to 262% at tolerable doses. Altogether, the 'scaffold hopping' demonstrated its productivity for obtaining new perspective antitumor drug candidates.

Structure-activity relationship studies of a series of antiviral and antibacterial aglycon derivatives of the glycopeptide antibiotics vancomycin, eremomycin, and dechloroeremomycin.

N-(adamantyl-1)methyl, N-(adamantyl-2), and N-(omega-aminodecyl) amides of vancomycin, eremomycin, and dechloroeremomycin aglycons and their des-(N-Me-D-Leu) derivatives were synthesized and their antibacterial and anti-HIV activities were investigated. Carboxamides with an intact peptide core demonstrated activity against glycopeptide-susceptible and -resistant bacteria (1-32 microM). N-(adamantyl-1)methylcarboxamide of eremomycin aglycons had good antiretroviral activity (1.6 microM against HIV-1). Compounds with destroyed peptide core [des-(N-Me-D-Leu)-aglycon amides] were inactive against both glycopeptide-sensitive and -resistant bacteria. (Adamantyl-1)methylamide of des-(N-Me-D-Leu)-eremomycin aglycon had good antiretroviral activity (EC50 of 5.5 microM for HIV-1 and 3.5 microM for HIV-2). (Adamantyl-1)methylamides of eremomycin aglycon and its des-(N-Me-d-Leu)-derivative are the most promising and selective antiretroviral agents. Their ability to induce bacterial resistance to glycopeptide antibiotics during prolonged administration may be expected to be very low or absent. This might make the use of these derivatives feasible in the prolonged therapy or prophylaxis of HIV infections.