Synthesis and biological evaluation of novel phenothiazine derivatives as non-peptide arginine vasopressin V2 receptor antagonists

A series of novel phenothiazine derivatives was synthesized and tested for arginine vasopressin receptor antagonist activity. They were synthesized as novel arginine vasopressin receptor antagonists from phenothiazine as a scaffold via successive acylation, reduction and acylation reactions. Their structures were characterized by 1HNMR, 13CNMRandHRMS, and biological activitywas evaluated by in vitro and in vivo studies. The in vitro binding assay indicated that several compounds are potent selective V2 receptor antagonists. Compounds with promising binding affinity to V2 receptors were selected to conduct the in vivo diuretic studies on Sprague-Dawley rats. Among them, 1n, 1r, 1t and 1v exhibited excellent diuretic activity, especially 1r and 1v. Therefore, 1r and 1v are potent novelAVP V2receptor antagonist candidates.     

Synthesis and electronic properties of (oligo)phenothiazine-ethynyl-hydro-C60 dyads

Ethynyl bridged (oligo)phenothiazine-C₆₀ dyads 2 can be readily synthesized by addition of the corresponding (oligo)phenothiazinyl lithium acetylides 1 to C₆₀ followed by protonation with acetic acid. Cyclovoltammetric data of 1 and 2 reveal that the (oligo)phenothiazinyl moieties (donor) and the fullerene fragment (acceptor) are electronically decoupled in ground state, yet, each additional phenothiazine lowers the HOMO-LUMO gap by 100 mV. Upon UV excitation the phenothiazinyl fluorescence is considerably quenched, presumably as a consequence of a charge separation by an intramolecular photo-induced electron transfer from phenothiazine to fullerene.     

Micelles catalyzed one pot regio- and chemoselective synthesis of benzo[a]phenazines and naphtho[2,3-d]imidazoles ‘in H2O’

An efficient, novel, and concise one pot regio- and chemoselective synthesis of benzo[a]phenazines (4) and naphtho[2,3-d]imidazoles (8) has been accomplished in excellent yields by nucleophilic substitution reaction of 2,3-dichloro-1,4-naphthoquinone (1) with o-phenylenediamine (2) and benzamidines (7) respectively ‘in H₂O’ using base and micelles (SDS) as catalyst. Analog reaction of 2,3-dichloro-1,4-naphthoquinone (1) with 2-aminobenzenethiol (9) under identical conditions led to formation of a mixture of benzo[b]phenothiazine (10), benzo[a]phenothiazine (11), and benzo[a]-1,4-benzothiazino-3,2-phenothiazine (12) in 17%, 23%, and 57% yields, respectively.     

First syntheses and electronic properties of (oligo)phenothiazine-C60 dyads

(Oligo)phenothiazine-C₆₀ dyads 3 can be readily synthesized by a three-component condensation-cycloaddition of the corresponding (oligo)phenothiazinyl carbaldehydes 1, N-hexyl glycine (2), and C₆₀. Cyclic voltammetry of 3 and reference compounds 4 shows that the phenothiazinyl moiety (donor) and the fullerene fragment (acceptor) are electronically decoupled in ground state. However, upon UV excitation the phenothiazinyl fluorescence is considerably quenched, presumably as a consequence of a charge separation by an intramolecular photo-induced electron transfer from phenothiazine to fullerene.     

A simple O-sulfated thiohydroximate molecule to be the first micromolar range myrosinase inhibitor

New non-hydrolyzable analogues of glucosinolates have been prepared. Myrosinase inhibition was observed with modified aglycon moieties, even bulky phenothiazine analogue 6 gave reasonable inhibition. The simplest structure 8 derived from dimethylaminoethanethiol has shown to be the most potent inhibitor with an IC₅₀ of 3.32 μM.     

Syntheses and DNA photocleavage by mono- and bis-phenothiazinium-piperazinexylene intercalators

Chromophore systems consisting of one (compound 5) or two (compound 6) phenothiazine rings covalently attached to a bis-piperazinexylene chain were synthesized and evaluated as DNA photocleaving agents. In the presence of DNA, the compounds were shown to monointercalate in their deaggregated forms and to strongly absorb red wavelengths of light. Reactions containing micromolar concentrations of compound produced robust photocleavage of plasmid DNA under near-physiological conditions of temperature and pH (22 °C and pH 7.0). Phenothiazines 5 and 6 increased the T_m of calf thymus DNA by 17 and 19 °C, indicating that significant levels of duplex stabilization were produced.     

Host-guest complexes of 3,5-dinitrobenzonitrile: channels and sandwich supramolecular architectures

Host-guest type complexes of 3,5-dinitrobenzonitrile, 1, with some hydrocarbons like benzene, naphthalene, p-xylene, o-xylene, and aza donor molecules (acridine, phenazine and phenothiazine) have been reported. In all the complexes, 1 forms a host network, yielding channels (in three-dimensional arrangement), which are filled by guest molecules, except in the complex of 1 with p-xylene. In this complex, although a host-guest type network is observed, the molecules of 1 and p-xylene are arranged in such a manner that the hydrocarbon is embedded between the layers of 1, like in inorganic clay structures. All the complexes have been characterized by single crystal X-ray diffraction methods.     

An efficient one-pot reaction for the synthesis of pyrazolones bearing a phenothiazine unit

A simple one-pot approach for the synthesis of new pyrazolones containing a phenothiazine unit is reported. Compound 4b was evaluated for its antiproliferative activity on a NCI-60 cancer cell line panel and exhibited selective cytostatic activity toward CCRF-CEM, HL-60(TB), K-562, MOLT-4, and RPMI-8226 leukemia cell lines.     

Glutamate sol-gel amperometric biosensor based on co-immobilised NADP+ and glutamate dehydrogenase

In this work the preparation and electrochemical characterisation of a new glutamate amperometric sol-gel biosensor is described. A carbon paste electrode was electrochemically modified with the phenothiazine dye methylene green (MG). The NADP⁺ and glutamate dehydrogenase were co-immobilised in a sol-gel matrix. When coupled to a flow injection system (FIA) the biosensor showed good electrocatalytic activity towards NADPH oxidation at the potential of + 0.3 V vs. Ag/AgCl; KCl sat., which represents a strong overpotential reduction. The biosensor yielded a linear response from 5.0 × 10^?5 to 1.0 × 10^?2 M glutamate concentration, with a detection limit of 5 × 10^?6 M and reproducibility of results better than 2.3% (RSD). Moreover, the implemented biosensor showed to be still useful after 7 months, 500 determinations.     

Supramolecular assemblies of Al3+ complexes with vitamin D3 (cholecalciferol) and phenothiazine. Encapsulation and complexation studies in β-cyclodextrin

Ternary assemblies of β-cyclodextrin with cholecalciferol (or vitamin D₃) or phenothiazine and Al³⁺ ions were studied. The stability constants of aluminium binary complexes with cholecalciferol or phenothiazine and of ternary assemblies (β-cyclodextrin, cholecalciferol or phenothiazine and Al³⁺) were determined using potentiometric titrations at 25 °C (I = 0.100 M). The ¹³C NMR spectra of the supramolecular structures in the solid state showed that ternary supramolecular structures associating β-cyclodextrin, cholecalciferol or phenothiazine and aluminium(III) ions were obtained. Finally, X-ray powder diffraction patterns showed that the ternary assemblies with phenothiazine are channel type inclusion complexes.     

Resonance Rayleigh scattering method for direct determination of polyacrylamide in water samples using basic phenothiazine dyes

Binding polyacrylamide (PAM) with some basic phenothiazine dyes such as methylene blue (MB), toluidine blue (TB) or Azure B (AB) etc. can result in a significant enhancement of resonance Rayleigh scattering (RRS). The maximum RRS wavelengths (λ_max) appear at 348, 340 and 342 nm for MB, TB, and AB systems, respectively. Accordingly, a new RRS method for the direct determination of PAM at nanogram levels has been established. The optimum conditions of these reactions, the influencing factors have been investigated. The RRS intensity is directly proportional to the concentration of PAM in the range of 0.040–5.0 μg/mL for three systems. The methods exhibit high sensitivities, and the detection limits are 15.9 ng/mL for MB system, 44.0 ng/mL for TB system, and 59.8 ng/mL for AB system. The selectivity of the method is investigated by using MB system owing to the highest sensitivity. Concentrations of PAM in tap water, synthetic water and practical waste water samples are determined satisfactorily. The reaction mechanism and RRS enhancement reasons are discussed.     

Studies in the heterocyclic series. XXI. A novel tetraaza-analog of phenothiazine

As a continuation of our search for new pharmaco-active phenothiazine compounds, the synthesis of 1,4,6,8-tetraazabenzo[b]phenothiazine ring system is described. Derivatives of this new heterocycle were prepared by converting 4,5-diamino-6-hydroxypyrimidine to 4,5-diaminopyrimidine-6-(1H)thione followed by the action of 2,3-dichloroquinoxaline in refluxing DMF or DMAC. The reaction of mixed nitric and sulfuric acids with 9-amino-12-chloro-1,4,6,8-tetraazabenzo[b]phenothiazine gave 9-amino-12-chloro-13-nitro-1,4,6,8-tetraazabenzo[b]phenothiazine 5-oxide in satisfactory yields. Diazotization of 9-amino-1,4,6,8-tetraazabenzo-[b]phenothiazine led to 1,4,6,8-tetraazatriazolo[4,5,1-kl]benzo[b]phenothiazine which is a new heterocyclic compound and the parent compound of this ring system. The mechanistic pathways to these compounds are also proposed.     

Syntheses and spectroscopic properties of energy transfer systems based on squaraines

The purpose of this project was to prepare fluorescent dyes that could absorb energy at relatively short wavelengths, and fluoresce in the near-IR region. To achieve this, copper- and palladium-mediated C-N couplings were used to prepare the ‘cassettes’, i.e the carbazole derivative 3b and the carbazole-, phenothiazine-, and phenoazine-squaraines 4b-d. These compounds have carbazole, phenothiazine, and phenoazine donor-components that absorb around about 300-320 nm, and squaraine acceptor-parts that fluoresce in the range 650-700 nm. The efficiencies of energy transfer from the donor to the acceptor, and the overall quantum yields of the cassettes were determined.     

Electro-oxidative polymerization of phenothiazine dyes into a multilayer-containing carbon nanotube on a glassy carbon electrode for the sensitive and low-potential detection of NADH

An electrochemical sensing platform was developed for the amperometric detection of β-nicotinamide adenine dinucleotide (NADH) through the integration of a multi-walled carbon nanotube (MWCNT) into electropolymerized phenothiazine dyes. The composite containing MWCNT and poly(phenothiazine) was prepared by electro-oxidative polymerization of phenothiazine derivatives, Azure B, Azure A and thionine, into an MWCNT/ poly(diallyldimethylammonium chloride) (PDDA) multilayer, which was constructed by electrostatic layer-by-layer assembly on a glassy carbon electrode. The three phenothiazine monomers used in this study exhibited similar electrochemical behaviors. Azure B was used extensively as a model monomer for the investigation. Electrochemical techniques and scanning electron microscopy were used to demonstrate that the porous composite was formed and that the carbon nanotube served as a nano-sized backbone for the loading of polymeric phenothiazine. The electrocatalytic current for NADH oxidation was enhanced as the number of layers increased, implying that the increase of NADH-accessible poly(phenothiazine) and the three-dimensional arrangement of the poly(phenothiazine)-coated MWCNT in the composite facilitated electron and NADH transfer. Under optimal conditions, the detection limit for NADH decreases to 7.0 × 10^?8?M at a potential of 0.1 V (versus Ag/AgCl) using a {MWCNT/PDDA}₈?poly(Azure B) composite modified glassy carbon electrode, with a response time of about 5 s. This work demonstrates that the electropolymerization of the phenothiazine monomer into a pre-formed multilayer containing MWCNT can be used for the controllable preparation of stable MWCNT/poly(phenothiazine) composites on electrode surfaces, which have the potential to provide a platform for electrochemical biosensors based on NAD⁺-dependent dehydrogenase enzymes.     

Inhibition of acrylic acid polymerization by phenothiazine and p-methoxyphenol. II. Catalytic inhibition by phenothiazine

Inhibition of acrylic acid by p-methoxyphenol fits a conventional stoichiometric mechanism but phenothiazine inhibits acrylic acid via a completely different, catalytic cycle which does not depend on the presence of oxygen. We propose that this mechanism may involve a pair of single electron transfer reactions between free radicals, phenothiazine N-radicalcation, and phenothiazine itself, the latter being cyclically regenerated. Arrhenius equations were derived for the rates of disappearance of inhibitor and oxygen in acrylic acid stabilized with phenothiazine and with p-methoxyphenol and also with phenothiazine in the absence of oxygen. The practical implication of high oxygen to p-methoxyphenol consumption ratios is quite important: if commercial acrylic acid (usually stabilized with p-methoxyphenol) is inadvertently heated during storage, the limiting substance determining the onset of polymerization will be the dissolved oxygen and not p-methoxyphenol unless oxygen (air) is being supplied to and dissolved in the liquid at a rate sufficient to overcome the rate of its consumption.     

A theoretical study on the structure and properties of phenothiazine derivatives and their radical cations

Semiempirical CNDO, AM1, PM3 and ab initio HF/STO-3G, HF/3-21G(d), and HF/6-31(d) methods were employed in the geometry optimization of the phenothiazine and the corresponding radical cation. The results obtained from the PM3 performances were as good as those from the ab initio calculations in the structure optimization of both phenothiazine and phenothiazine radical cation. The PM3 method was used to optimize the structures of a series of N-substituted phenothiazine derivatives and their radical cations. The PM3-optimized results were then analyzed with the ab initio calculation at the 6-311G(d,p) level, which yielded the total energy, frontier molecular orbitals, dipole moments, and charge and spin density distributions of the phenothiazine derivatives and their radical cations.     

Synthesis and characterization of poly[N-((10-phenothiazinyl)-6-hexanoyl)ethylenimine] and N,N-diethyl-6-(10-phenothiazinyl)-hexanamide

A new oxazoline monomer was made containing a chloroalkyl substituent which can be transformed to other functional groups by nucleophilic substitution. Oxazoline monomer containing the N-phenothiazinyl substituent was made by reacting lithiated phenothiazine with the chloroalkyl substituted oxazoline and subsequently polymerized. N,N-diethyl-6-chlorohexanamide was synthesized and N,N-diethyl-6-(10-phenothiazinyl)-hexanamide, a model compound for the phenothiazine polymer, was made by reacting lithiated phenothiazine with this chloroamide. TCNQ did not complex with the polymer. The iodine and perchlorate complexes of the phenothiazine polymer had conductivities of 4.4 × 10 ^?8 and 6.9 × 10^?6 S/cm, respectively, at room temperature. Each of these are higher than the corresponding values reported for complexes of the analogous model compounds or 3-substituted phenothiazine polymer reported earlier.¹³, ²² This was attributed to the very short chain repeat distance for the present, symmetrically substituted polymer.     

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

The oxidative degradation of phenothiazine derivatives (PTZ) by manganese(III) was studied in the presence of a large excess of manganese(III)-pyrophosphate (P₂O₇ ²⁻), phosphate (PO₄ ³⁻), and H⁺ ions using UV–vis. spectroscopy. The first irreversible step is a fast reaction between phenothiazine and manganese pyrophosphate leading to the complete conversion to a stable phenothiazine radical. In the second step, the cation radical is oxidized by manganese to a dication, which subsequently hydrolyzes to phenothiazine 5-oxide. The reaction rate is controlled by the coordination and stability of manganese(III) ion influenced by the reduction potential of these ions and their strong ability to oxidize many reducing agents. The cation radical might also be transformed to the final product in another competing reaction. The final product, phenothiazine 5-oxide, is also formed via a disproportionation reaction. The kinetics of the second step of the oxidative degradation could be studied in acidic phosphate media due to the large difference in the rates of the first and further processes. Linear dependences of the pseudo-first-order rate constants (k _obs) on [Mn^III] with a significant non-zero intercept were established for the degradation of phenothiazine radicals. The rate is dependent on [H⁺] and independent of [PTZ] within the excess concentration range of the manganese(III) complexes used in the isolation method. The kinetics of the disproportionation of the phenothiazine radical have been studied independently from the further oxidative degradation process in acidic sulphate media. The rate is inversely dependent on [PTZ^+.], dependent on [H⁺], and increases slightly with decreasing H⁺ concentration. Mechanistic consequences of all these results are discussed.     

Synthesis of some phenothiazinyl and carbazolyl pyrylium salts

2,6-Diphenyl-4H-pyran-4-one in the presence of phosphorus oxychloride reacted with phenothiazine to give a pyryliurn salt which was bonded in the 4-position to the nitrogen atom of phenothiazine. Carbazole gave a similar type of product. When the N-methyl derivatives of phenothiazine and carbazole were allowed to react under the same conditions, the coupling took place on the phenyl ring para to the nitrogen atom. In contrast to phenothiazine, benzo[a]-phenothiazine gave a product arising by coupling into the phenyl ring.     

Heterocyclization of N-propenyl-substituted phenothiazines and phenoxazines using electrophiles in an anhydrous medium

10-Propenylphenothiazine reacts with a catalytic amount of BF₃·Et₂O in dry ethyl acetate via intramolecular heterocyclization of an intermediate dimeric cation to give mainly 1-ethyl-2-methyl-3-(phenothiazin-10-yl)-2,3-dihydro-1H-pyrido[3,2,1-k,l]phenothiazine and a minor product through fission of phenothiazine which is 1-ethyl-2-methyl-1H-pyrido[3,2,1-k,l]phenothiazine. Under similar conditions 10-propenylphenoxazine gave an oligomer (degree of polymerization 4.4) and the minor product 1-ethyl-2-methyl-1H-pyrido[3,2,1-k,l]phenoxazine likely formed similarly to the phenothiazine analog from the corresponding product of intramolecular heterocyclization (the latter not being observed in the reaction mixture). Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1855–1860, December, 2008.