Synthesis and Antimalarial Property of Orally Active Phenoxazinium Salts

Phenoxazinium salts were found to display good antimalarial efficacy in vivo against Plasmodium berghei. Several compounds provided 100% parasitemia clearance at a dose of 20-30 mg kg-1x4 days (ip) and good survival effects without obvious acute toxicity. They also showed excellent potency by oral administration. A preliminary pharmacokinetic study revealed that the oral availability of 1a was excellent.

Discovery of diaryl imidazolidin-2-one derivatives, a novel class of muscarinic M3 selective antagonists (Part 2)

Synthesis and biological activity of a novel class of quaternary ammonium salt muscarinic M3 receptor antagonists, showing high selectivity versus the M2 receptor, are described. Selected compounds exhibited potent anticholinergic properties, in isolated guinea-pig trachea, and good functional selectivity for trachea over atria. In vivo, the same compounds potently inhibited acetylcholine-induced bronchoconstriction after intratracheal administration in the guinea pig.

Synthesis and antitubercular activity of quaternized promazine and promethazine derivatives

Quaternized chlorpromazine, triflupromazine, and promethazine derivatives were synthesized and examined as antitubercular agents against both actively growing and non-replicating Mycobacterium tuberculosis H37Rv. Impressively, several compounds inhibited non-replicating M. tuberculosis at concentrations equal to or double their MICs against the actively growing strain. All active compounds were non-toxic toward Vero cells (IC50 > 128 microM). N-Allylchlorpromazinium bromide was only weakly antitubercular, but replacing allyl with benzyl or substituted benzyl improved potency. An electron-withdrawing substituent on the phenothiazine ring was also essential. Branching at the carbon chain decreased antitubercular activity. The optimum antitubercular structures possessed N-(4- or 3-chlorobenzyl) substitution on triflupromazine.

Fluoride relay: a new concept for the rapid preparation of anhydrous nucleophilic fluoride salts from KF

Fluoride relay is used to generate exceptionally nucleophilic fluoride reagents from KF on a time scale commensurate with radiotracer synthesis.

Control of Interchain Contacts, Solid-State Fluorescence Quantum Yield, and Charge Transport of Cationic Conjugated Polyelectrolytes by Choice of Anion

Simple procedures are provided for exchanging charge-compensating ions in conjugated polyelectrolytes by progressive dilution of the original species and for determining the degree of ion exchange by using X-ray photoelectron spectroscopy. By using these methods, the bromide ions in poly[(9,9-bis(6'-N,N,N-trimethylammoniumbromide)hexyl)fluorene-co-alt-4,7-(2,1,3-benzothiadiazole)]were exchanged with BF4-, CF3SO3-, PF6-, BPh4-, and B(3,5-(CF3)2C6H3)4- (BArF4-). Absorption, photoluminescence (PL), and PL quantum yields (Phi) were measured in different solvents and in solid films cast from methanol. Examination of the resulting trends, together with the spectral bandshapes in different solvents, suggests that increasing the counteranion (CA) size decreases interchain contacts and aggregation and leads to a substantial increase of Phi in the bulk. Size analysis of polymers containing Br- and BArF4- in water by dynamic light scattering techniques indicates suppression of aggregation by BArF4-. Nanoscale current-voltage measurements of films using conducting atomic force microscopy show that hole mobilities and, more significantly, charge injection barriers are CA dependent. These results show that it is possible to significantly modify the optoelectronic properties of conjugated polyelectrolytes by choosing different counterions. A parent conjugated backbone can thus be fine-tuned for specific applications.

Complexation of Quaternary Ammonium Ions by Tetraester Derivatives of [3.1.3.1]Homooxacalixarene in Mobile and in Fixed Conformation

In the tetraalkylation of p-tert-butyl[3.1.3.1]homooxacalixarene with BrCH2CO2R and K2CO3 in acetone, the initially formed cone conformer is converted into the more stable 1,4-alternate conformer when R = Me or Et, but not when R = i-Pr or t-Bu. In the case of R = i-Pr, derivatives in fixed 1,4-alternate conformation and in partial cone conformation were also isolated. Compounds in fixed cone conformation are good ligands for tetramethylammonium, acetylcholine, and N-methylpyridinium salts in CDCl3, but the partial cone isomer proved to be somewhat better and even the 1,4-alternate conformer turned out to be active. The possible involvement of the ester functions as additional binding sites is discussed; moreover, an insight into the energetics of the complexation and conformational isomerization processes is given.

Synthesis of cationic conjugated polymers for use in label-free DNA microarrays

We describe the synthesis of poly[9,9'-bis(6''-N,N,N-trimethylammonium)hexyl)fluorene-co-alt-4,7-(2,1,3-benzothiadiazole) dibromide] (PFBT), a cationic, water-soluble conjugated polymer used in label-free DNA microarrays. This polymer was designed to have a maximum absorbance of close to 488 nm, which meets the excitation wavelength of most commercial microarray readers, and to have efficient emission in the solid state. Starting from commercially available chemicals, five steps are required to synthesize PFBT. The first step involves treatment of 2,7-dibromofluorene in 50% potassium hydroxide solution with excess 1,6-dibromohexene at 75 degrees C for 25 min to afford 2,7-dibromo-9,9-bis(6'-bromohexyl)fluorene (A). In the second step, a mixture of A, bis(pinacolato)diborane and potassium acetate in dioxane is stirred at 85 degrees C for 12 h to afford bis[9,9'-bis(6''-bromohexyl)-fluorenyl]-4,4,5,5-[1.3.2]dioxaborolane (B). The third step involves bromination of 2,1,3-benzothiadiazole using bromine in the presence of hydrogen bromide to afford 4,7-dibromo-2,1,3-benzothiadiazole (C). Suzuki cross-coupling copolymerization of B and C affords the charge-neutral precursor of PFBT. In the final step, quaternization of pendant groups using trimethylamine yields PFBT. Each step takes up to 3 days, including the time required for product purification. The overall protocol requires approximately 3 weeks.

Synthesis and Radioligand Binding Studies of Methoxylated 1,2,3,4-Tetrahydroisoquinolinium Derivatives as Ligands of the Apamin-Sensitive Ca2+-Activated K+ Channels

Several methoxylated 1,2,3,4-tetrahydroisoquinoliniums derived from N-methyl-laudanosine and N-methyl-noscapine were synthesized and evaluated for their affinity for apamin-sensitive binding sites. The quaternary ammonium derivatives have a higher affinity with regard to the tertiary amines. 6,7-Dimethoxy analogues possess a higher affinity than the 6,8- and 7,8-dimethoxy isomers. A 3,4-dimethoxybenzyl or a 2-naphthylmethyl moiety in C-1 position are more favorable than a 3,4-dimethoxyphenethyl group. Smaller groups such as propyl or isobutyl are unfavorable. In 6,7-dimethoxy analogues, increasing the size and lipophilicity with a naphthyl group in the C-1 position leads to a slight increase of affinity, while the same group in the 6,7,8-trimethoxy series is less favorable. The 6,7,8-trimethoxy derivative 3f is the first tertiary amine in the series to possess an affinity close to that of N-methyl-laudanosine and N-methyl-noscapine. Moreover, electrophysiological studies show that the most effective compound 4f blocks the apamin-sensitive afterhyperpolarization in rat dopaminergic neurons.

Semiautomated synthesis of a novel [18F] amine fluorocyanoborane for PET imaging studies. Radiosynthesis and in vivo characterization in rats

A novel fluorine-18 labeled amine fluorocyanoborane derivative was synthesized from the bromo-derivative precursor in 22% radiochemical yield. The [18F] labeling was accomplished by a semiautomatic method that is based on the synthesis of Ag 18F from Ag2CO3 and H 18F in a platinum dish followed by sonication of the bromo-precursor with Ag 18F in dry benzene to produce [18F] labeled amine fluorocyanoborane which was used with no further purification. A total of 50 microCi of the [18F] labeled amine fluorocyanoborane was injected into normal, female Sprague-Dawley rats (250-300 g) via the tail vein and monitored by Positron emission tomography (PET)/CT to detect its biodistribution in the rat body. The images showed an uptake of this compound in the bones of rats.

Synthesis of new analogues of salacinol containing a pendant hydroxymethyl group as potential glycosidase inhibitors

The synthesis of new analogues of the naturally occurring glycosidase inhibitor, salacinol, and its ammonium analogue, ghavamiol is described. These analogues contain an additional hydroxymethyl group at C-1, which was intended to form additional polar contacts within the active site of glycosidase enzymes. The target zwitterionic compounds were synthesized by means of nucleophilic attack at the least hindered carbon atom of 2,4-O-benzylidene-l (or d)-erythritol 1,3-cyclic sulfate by 2,5-anhydro-1,3:4,6-di-O-benzylidene-2,5-dideoxy-5-thio (or 1,5-imino)-l-iditol.

Synthesis of a quaternary amine anion exchange resin and study [of] its adsorption behaviour for chromate oxyanions

Glycidyl methacrylate/N,N'-methylene bis-acrylamide (GMA/MBA) was prepared and allowed to react with tetraethylenepentamine (TEP) to give glycidyl methacrylate amine resin (RPA) followed by treatment with glycidyl trimethylammonium chloride (GTA) to give glycidyl methacrylate resin bearing quaternary ammonium chloride moieties (RQA). Zeta potential measurements showed that RQA particles are positively charged over pH 2-10 indicating the strong basic nature of the quaternary amine sites. The effect of pH on the recovery of chromate by RPA and RQA was examined. The results indicated that RQA is an efficient sorbent for chromate from both acidic and basic media. The repeated use of RQA was tested through stripping the adsorbed chromate using a mixture of 0.05 NaOH and 2 M NaCl in the case of the uptake from acidic media and using 2 M NaCl solution in the case of alkaline solutions.

Rational Design, Synthesis, and Application of a New Receptor for the Molecular Recognition of Tricarboxylate Salts in Aqueous Media

A rational design of a tripodal receptor for the molecular recognition of tricarboxylate salts in aqueous media, based on squaramide, has been performed using high-level DFT calculations (RI-BP86/SVP level of theory) in solution using the COSMO treatment, including some preliminary ab initio calculations at the higher RI-MP2/TZVP level of theory, comparing the ability of squaramide to bind carboxylate salts with two widely used guanidinium salts. The tripodal receptor has been synthesized using a new methodology that has been recently reported by some of us, and its capability of recognizing several mono-, di-, and tricarboxylate salts has been studied experimentally by means of microcalorimetry experiments in a very high competitive media, H(2)O:EtOH 1:3. These experiments give enthalpic and entropic data, which are unfortunately scarce in the literature of molecular recognition of anions. Finally, a fluorimetric ensemble of the receptor with fluorescein has been found to be useful for the fluorimetric determination of zinc citrate in a commercial toothpaste using competition assays.

Preparation, single-crystal X-ray diffraction and high-resolution NMR spectroscopic analyses of N-[(1,4-anhydro-5-deoxy-2,3-O-isopropylidene-d,l-ribitol)-5-yl]trimethylammonium iodide

The synthesis and isolation of 1,4-anhydro-5-deoxy-5-iodo-2,3-O-isopropylidene-D,L-ribitol and N-[(1,4-anhydro-5-deoxy-2,3-O-isopropylidene-D,L-ribitol)-5-yl]trimethylammonium iodide are described. The products were examined by (1)H, (13)C NMR spectroscopy, and N-[(1,4-anhydro-5-deoxy-2,3-O-isopropylidene-D,L-ribitol)-5-yl]trimethylammonium iodide was additionally analyzed by X-ray crystallography.

Ionene-dynamically coated capillary for analysis of urinary and recombinant human erythropoietin by capillary electrophoresis and online electrospray ionization mass spectrometry

In this article, a series of ionene polymers were synthesized and used to coat fused-silica capillaries for the separation of recombinant and urinary human erythropoietin (rhEPO and uEPO) standards by CE. The influence of the charge density of coatings on the separation of rhEPO and uEPO glycoforms was investigated. Then, we further studied the method for fast separation and detection of rhEPO and uEPO standards by CE-ESI-MS. The influence of several CE and MS operating parameters, such as the concentration of CE running buffer, applied external pressure, and the composition and flow rate of sheath liquid on CE-ESI-MS was studied. The results demonstrated that when the capillary was permanently coated with 6,6-ionene and the pH value of acetic acid-ammonium acetate running buffer was 4.80 and 5.50, respectively, a significantly reproducible separation was achieved for rhEPO and uEPO glycoforms. In the online CE-ESI-MS experiments, we not only achieved the online MS signal of uEPO, but also obtained baseline separation of three major rhEPO glycoforms successfully and reproducibly on the 6,6-ionene-coated capillaries. Furthermore, the standard mixture of rhEPO and uEPO was separated, and two incompletely resolved peaks that were identified to be rhEPO and uEPO by the unique MS "fingerprint" were obtained. Additionally, the molecular weight of rhEPO and uEPO were verified and compared to the results by MALDI-TOF-MS. It can be concluded that, in contrast to other indirect methods, the online CE-ESI-MS technique with the combination of the advantages of both CE and MS shows great potential for the separation and detection of rhEPO doping directly in competitive sports.

Synthesis and biological properties of gemini quaternary ammonium compounds, 5,5'-[2,2'-(alpha,omega-polymethylnedicarbonyldioxy)diethyl]bis-(3-alkyl-4-methylthiazolium iodide) and 5,5'-[2,2'-(p-phenylenedicarbonyldioxy)diethyl]bis(3-alkyl-4-methylthiazolium bromide)

We synthesized gemini quaternary ammonium compounds (gemini QACs) having two thiazolium moieties in a molecule, 5,5'-[2,2'-(alpha,omega-polymethylnedicarbonyldioxy)diethyl]bis(3-alkyl-4-methylthiazolium iodide) (5DEBT-m,n), on which the carbon number of the methylene chain linking the two thiazoles (m) is 2, 6 or 8 and that of the alkyl group (n) is 8, 10, 12, 14 or 16. 5,5'-[2,2'-(p-Phenylenedicarbonyldioxy)diethyl]bis(3-alkyl-4-methylthiazolium bromide) (5DEBT-P,n) was then synthesized, which is composed of a p-phenylene as the methylene spacer. For five gemini QAC series, in addition to the previously described 5DEBT-4,n to the four new compound series, their antimicrobial activities were determined. 5DEBT-m,10 and -P,10 exhibited a wide and strong bacteriostatic activity against gram-negative and -positive bacteria, fungi and then yeast in comparison with N-tetradecyl-5-(2-hydroxyethyl)-4-methylthiazolium iodide as a mono-QAC. The bactericidal activity of the 5DEBT series against Escherichia coli IFO 12713 and Staphylococcus aureus IFO 12732 was investigated on the basis of the effects of their alkyl chain length and their molecular hydrophobicity. It was found that the effect of theses factors on their activity significantly changes by the difference between the gram-negative and -positive bacteria. Although against the gram-negative bacterium, the change in the activity due to extension of the alkyl group for each compound affected the kind of methylene spacer, against the gram-positive bacterium, it was almost equal in spite of the methylene spacer. This result could be responsible for the bactericidal mechanism of the gemini QACs being influenced by the diversity of the steric structure participating in the methylene chain length and by the bacterium cell surface hydrophobicity.

Synthesis and properties of chiral ammonium-based ionic liquids

New chiral ammonium-based ionic liquids containing the (1R,2S,5R)-(-)-menthyl group can be easily and efficiently prepared under ambient conditions. The preparation and characterization of trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium salts is reported. The salts have been demonstrated to be air- and moisture-stable under ambient conditions and can be readily used in a variety of standard experimental procedures. The single-crystal X-ray structure of butyldimethyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride has been determined. The chiral, room-temperature ionic liquids have been characterized by physical properties such as specific rotation, density, viscosity, thermal degradation, and glass transition temperature. Trialkyl[(1R,2S,5R)-(-)-menthoxymethyl]ammonium chloride prototype ionic liquids have also been found to exhibit strong antimicrobial and high antielectrostatic activities.

An Infrared νNH Scale for Weakly Basic Anions. Implications for Single-Molecule Acidity and Superacidity

The N-H stretching frequencies of tri-n-octylammonium salts are reported for a series of weakly basic anions (A(-)), many of which are the conjugate bases of known strong acids and superacids. Data have been collected primarily in carbon tetrachloride, where Oct(3)N(+)-H...A(-) contact ion pairs are formed. In the more polar solvent 1,2-dichloroethane, some salts form both contact and solvent-separated ion pairs. Salts have also been studied in crystalline form or as oils. In general, the nuNH frequencies decrease in the order fluoroanions > carboranes > oxyanions, reflecting the relative basicities of the anions. By inference, the data reflect differences in the acidity of the corresponding conjugate acids (HA). This qualitative indicator of acid strength is useful because it reflects acidity on an individual molecule basis rather than in bulk. In this respect, it provides a condensed-phase analogy to gas-phase ("intrinsic") acidity and gives insight into the aggregation phenomena that determine bulk acidity. The data also reveal the importance of the chemical stability of conjugate base anions in attaining high acidity and suggest where acids stronger than those presently known may be discovered.

Tailoring of horseradish peroxidase activity in cationic water-in-oil microemulsions

Horseradish peroxidase (HRP) in cationic water-in-oil (W/O) microemulsions has always been ignored in reverse micellar enzymology, mainly because cationic surfactants are inhibitors of enzyme peroxidase. In the present study, for the first time, we have successfully introduced the cationic W/O microemulsion as an attractive host for efficient HRP activity. To this notion, much improved activity of HRP was observed in the W/O microemulsion of cetyltrimethylammonium bromide (CTAB) with an increase in n-hexanol concentration and W0 ([water]/[surfactant]), presumably due to the increased interfacial area of the microemulsions. In support of our above observation, six surfactants were synthesized with an increased headgroup size where the methyl groups of CTAB were subsequently replaced by the n-propyl and 2-hydroxyethyl groups, respectively, to prepare mono-, di-, and tripropylated/hydroxyethylated n-hexadecylammonium bromide. The peroxidase activity enhanced with headgroup size and also followed an overall trend similar to that found in the case of CTAB. Possibly, the reduced positive charge density at the augmented interfacial area by means of increase, either in headgroup size, cosurfactant concentration, and/or W0, is not capable of inactivating HRP. Also, the larger space at the interface may facilitate easier solubilization of the enzyme and increase the local concentration of enzyme and substrate, leading to the higher activity of HRP. The best activity was obtained with surfactant N-hexadecyl-N,N,N-tripropylammonium bromide, the highest ever found in any cationic W/O microemulsions, being almost 3 times higher than that found in water. Strikingly, this observed highest activity is comparable with that observed in an anionic bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT)-based system, the best W/O microemulsions used for HRP.

Correlation of antifungal activity with fungal phospholipase inhibition using a series of bisquaternary ammonium salts

A series of bisquaternary ammonium salts with a 12-carbon spacer between the positive charges were synthesized, and their antifungal activity has been investigated. Compounds with butyl, pentyl, and isopentyl headgroups were the most potent antifungal agents with MICs in the range of 2.2-5.5 microM against both Cryptococcus neoformans and Candida albicans. The antifungal activity of these compounds correlated with their inhibition of cryptococcal phospholipase B1 (PLB1), a newly identified virulence factor. This indicates that the mode of action of these compounds may be inhibition of the fungal PLB1 enzyme, further validating this enzyme as a target for the development of novel antifungal therapies.

Syntheses and antimicrobial activities of a series of new bis-quaternary ammonium compounds

A series of new bis-quaternary ammonium compounds (bis-QACs), 4,4'-(2,9-dioxadecane) bis(1-alkylpyridinium bromide)s, 3,3'-(2,9-dioxadecane)bis(1-alkylpyridinium bromide)s and 3,3'-(2,7-dioxaoctane)bis(1-decylpyridinium bromide) was synthesized. The compounds were evaluated by their activities against bacteria, molds and yeasts; the activities were expressed as the minimum inhibitory concentrations (MIC) and/or the minimum bactericidal concentrations (MBC). Compound 4,4'-(2,9-dioxadecane) bis(1-decylpyridinium bromide) had MIC values which exceeded those of benzalkoniumchloride and thiabendazole. It was in vitro active against a broad spectrum of Gram-negative and Gram-positive bacteria, against yeasts and some molds, it had high solubility and thermal decomposition temperature. The relationships between structure and biological activity of the tested bis-QACs are discussed.

Shamrock surfactants with terminal carboxylate headgroups and a central phosphorodithioate or quaternary ammonium headgroup

Surfactants 3 (tripotassium O,O'-di-[11-(carboxylato)undecyl]phosphorodithioate) and 4 (sodium 12-[dimethyl-(11-carboxylatoundecyl)ammonio]dodecanoate), which are new shamrock surfactants, were prepared and characterized. Shamrock surfactants represent a novel class of surfactants that contain a central headgroup connected to two flanking headgroups by hydrocarbon chains; they do not contain long-chain alkyl groups. Surfactants 3 and 4 were characterized in water by measurement of their Krafft temperatures and critical aggregation concentrations, and their aggregates were studied by 1H and 31P NMR spectroscopy, dynamic laser light scattering, and phase-contrast optical microscopy. Aqueous 3 and 4 were also studied by cryoetch high-resolution scanning electron microscopy, which revealed fences with interposed lacelike patterns for the former and compartments formed by irregular fences for the latter. Coacervates were likely formed upon the undisturbed hydration of 3 and 4, as determined by phase-contrast optical microscopy.

Sequential Formation of a Ternary Complex among Dihexylammonium, Cucurbit[6]uril, and Cyclodextrin with Positive Cooperativity

A unique ternary 1:1:1 cucurbit[6]uril (CB[6])-cyclodextrin (CD)-dihexylammonium (DHA) complex was designed and noncovalently synthesized in stepwise fashion: first, CB[6] interacts strongly with DHA to form a 1:1 complex; second, addition of CD into the solution of the 1:1 complex leads to the exclusive formation of the 1:1:1 ternary complex. The ternary complex was characterized by various experimental techniques including ITC, NMR, and ESI-MS.

Co-digestion of ruminal content and blood from slaughterhouse industries: influence of solid concentration and ammonium generation

At the present time, organic solid wastes from industries and agricultural activities are considered to be promising substrates for biogas production via anaerobic digestion. Moreover solids stabilisation is required before reutilization or disposal. Slaughterhouses are among the most important industries in Uruguay and produce 150,000 tons of ruminal content (RC) and 30,000 tons of blood per year. In order to determine the influence of the solids and blood contents, the ammonia inhibition and the inoculum adaptation co-digestion batch tests were performed. A set of experiences with TS concentration of 2.5%, 5% and 7.5% and different ratios of RC/blood were carried out using an inoculum from an UASB reactor. In all experiences fast blood hydrolisation was observed. A higher methane production was detected in the experiences with higher TS content. However, the fraction of solids degradation was lower in these experiences. A plateau in the biogas production was found. The free ammonia level, which was above the reported inhibitory levels, could explain this behaviour. After the inhibition period the biogas production restarted probably due to the biomass acclimatisation to the ammonia. In order to determine the inoculum adaptation a new experiment was performed. The inoculum used was the sludge coming from the first set of experiences. Based upon batch tests a 3.5 m3 pilot reactor was designed and started up. Ammonia inhibition was avoided by the start-up strategy and in two weeks the biogas production was 3.5 m3/d. The VS stabilisation with a solid retention time of 20 days was of 43%. The pilot reactor working at steady state had a TS concentration of 3-4% with a ratio of RC/blood of 10:1 at the entrance.

In Vivo Studies of Dialkynoyl Analogues of DOTAP Demonstrate Improved Gene Transfer Efficiency of Cationic Liposomes in Mouse Lung

A novel set of dialkynoyl analogues of the cationic, gene delivery lipid DOTAP (1) was synthesized. Structure-activity studies demonstrate that replacement of the cis-double bonds of DOTAP with triple bonds in varying positions alters both the physical properties of the resultant cationic liposome-DNA complexes and their biological functionalities, both in vitro and in vivo. Particularly, in vivo studies demonstrate that pDNA transfection of mouse lung endothelial cells with lead analogue DS(14-yne)TAP (4):cholesterol lipoplexes exhibits double the transfection level with less associated toxicity relative to the well-established DOTAP:cholesterol system. In fact, 4:cholesterol delivers up to 3 times the dose of pDNA in mice than can be tolerated by DOTAP, leading to nearly 3 times greater marker-gene expression. X-ray diffraction studies suggest that lipoplexes containing analogue 4 display increased stability at physiological temperatures. Our results thus suggest that analogue 4 is a potentially strong candidate for the gene therapy of lung tumors.

Antitrypanosomal, Antileishmanial, and Antimalarial Activities of Quaternary Arylalkylammonium 2-Amino-4-Chlorophenyl Phenyl Sulfides, a New Class of Trypanothione Reductase Inhibitor, and of N-Acyl Derivatives of 2-Amino-4-Chlorophenyl Phenyl Sulfide

Quaternization of the nitrogen atom of 2-amino-4-chlorophenyl phenyl sulfide analogues of chlorpromazine improved inhibition approximately 40-fold (3',4'-dichlorobenzyl-[5-chloro-2-phenylsulfanyl-phenylamino)-propyl]-dimethylammonium chloride inhibited trypanothione reductase from Trypanosoma cruzi with a linear competitive Ki value of 1.7 +/- 0.2 microM). Molecular modelling explained docking orientations and energies by: (i) involvement of the Z-site hydrophobic pocket (roughly bounded by F396', P398', and L399'), (ii) ionic interactions for the cationic nitrogen with Glu-466' or -467'. A series of N-acyl-2-amino-4-chlorophenyl sulfides showed mixed inhibition (Ki, Ki' = 11.3-42.8 microM). The quaternized analogues of the 2-chlorophenyl phenyl sulfides had strong antitrypanosomal and antileishmanial activity in vitro against T. brucei rhodesiense STIB900, T. cruzi Tulahuan, and Leishmania donovani HU3. The N-acyl-2-amino-4-chlorophenyl sulfides were active against Plasmodium falciparum. The phenothiazine and diaryl sulfide quaternary compounds were also powerful antimalarials, providing a new structural framework for antimalarial design.