Improved synthesis of V-PYRRO/NO, a liver-selective nitric oxide prodrug, and analogues

The reported synthesis of O²-vinyl 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (V-PYRRO/NO), a hepatoprotective agent, was cumbersome and limited by a poor overall yield of 4% from sodium 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (PYRRO/NO). We report an improved synthesis of V-PYRRO/NO in two steps with a significantly higher overall yield of 40% from PYRRO/NO. Using this protocol, a number of structural analogues of V-PYRRO/NO were prepared in good yields.     

Arylation of Sensitive 1-(Pyrrolidin-1-yl)-diazen-1-ium-diolate in Ionic Liquids

The purpose of this research was to investigate the stability and reactivity of 1-(pyrrolidin-1-yl)diazen-1-ium-1,2-diolate (PYRRO/NO) in dimethylformamide (DMF, as the reference solvent) and compare them to those obtained using different ionic liquids. The results of our experiments showed that PYRRO/NO is more stable (based on reactivity) in ionic liquid [EMIM][Ms] (with reaction yields up to 52%) than in DMF, that substitution products can be separated directly and quantitatively from the ionic liquid using a single flash-column separation, and that the ionic liquids can also be recovered and reused in a second iteration of the same reaction to achieve similar yields.     

Microchip electrophoresis with amperometric detection for the study of the generation of nitric oxide by NONOate salts

Microchip electrophoresis (ME) with electrochemical detection was used to monitor nitric oxide (NO) production from diethylammonium (Z)-1-(N,N-diethylamino)diazen-1-ium-1,2-diolate (DEA/NO) and 1-(hydroxyl-NNO-azoxy)-L-proline disodium salt (PROLI/NO). NO was generated through acid hydrolysis of these NONOate salts. The products of acid hydrolysis were introduced into a 5-cm separation channel using gated injection. The separation was accomplished using reverse polarity and a background electrolyte consisting of 10 mM boric acid and 2 mM tetradecyltrimethylammonium bromide, pH 11. Electrochemical detection was performed using an isolated potentiostat in an in-channel configuration. Potentials applied to the working electrode, typically higher than +1.0 V vs. Ag/AgCl, allowed the direct detection of nitrite, NO, DEA/NO, and PROLI/NO. Baseline resolution was achieved for the separation of PROLI/NO and NO while resolution between DEA/NO and NO was poor (1.0 ± 0.2). Nitrite was present in all samples tested.     

Photoinduced release of nitroxyl and nitric oxide from diazeniumdiolates

Aqueous photochemistry of diazen-1-ium-1,2,2-triolate (Angeli's anion) and (Z)-1[N-(3-aminopropyl)-N-(3-aminopropyl)amino]diazen-1-ium-1,2-diolate (DPTA NONOate) has been investigated by laser kinetic spectroscopy. In neutral aqueous solutions, 266 nm photolysis of these diazeniumdiolates generates a unique spectrum of primary products including the ground-state triplet (3NO-) and singlet (1HNO) nitroxyl species and nitric oxide (NO*). Formation of these spectrophotometrically invisible products is revealed and quantitatively assayed by analyzing a complex set of their cross-reactions leading to the formation of colored intermediates, the N2O2*- radical and N3O3- anion. The experimental design employed takes advantage of the extremely slow spin-forbidden protic equilibration between 3NO- and 1HNO and the vast difference in their reactivity toward NO*. To account for the kinetic data, a novel combination reaction, 3NO-+1HNO, is introduced, and its rate constant of 6.6x10(9) M-1 s-1 is measured by competition with the reduction of methyl viologen by 3NO-. The latter reaction occurring with 2.1x10(9) M-1 s-1 rate constant and leading to the stable, colored methyl viologen radical cation is useful for detection of 3NO-. The distributions of the primary photolysis products (Angeli's anion: 22% 3NO-, 58% 1HNO, and 20% NO*; DPTA NONOate: 3% 3NO-, 12% 1HNO, and 85% NO*) show that neither diazeniumdiolate is a highly selective photochemical generator of nitroxyl species or nitric oxide, although the selectivity of DPTA NONOate for NO* generation is clearly greater.     

E/Z conformation and the vibrational spectroscopy of Me2NN(O)=NOMe

The simple neutral diazenium diolate, O2-methyl-1-(N, N-dimethylamino)diazen-1-ium-1,2-diolate, [Me2NN(O)=NOMe], was experimentally examined by vibrational spectroscopy and the results compared to the theoretically calculated values in an effort to detect both Z and E conformers which result from the stereochemistry of the N=N multiple bond. Room-temperature Raman and infrared spectra were measured and the results compared with the values calculated theoretically with MP2 and density functional techniques (B3LYP). An analysis of the observed frequencies suggests that, down to a detection limit of about 1/1000, only a small quantity of trans (E) diazeniumdiolate, <0.05%, may be present at room temperature.     

Electrochemical analysis of the kinetics of nitric oxide release from two diazeniumdiolates in buffered aqueous solutions

We have investigated in this work the kinetics of NO-release from two commercially available and commonly used diazeniumdiolates (so-called NONOates), namely diethylammonium (Z)-1-(N,N-diethylamino)-diazen-1-ium-1,2-diolate (DEA-NONOate) and (Z)-1-[N-(2-aminoepropyl)-N-(2-ammoniopropyl)amino]-diazen-1-ium-1,2-diolate (PAPA-NONOate) by electrochemical measurements. This choice was driven by the distinctive half-life of each compound (2–20 min at 37 °C for DEA- and PAPA-NONOate, respectively) that allow covering a relatively wide range of rate of NO-release. The release of NO from NONOate decomposition was followed using a home-made NO-sensitive electrochemical sensor. The electrochemical features of the starting NONOates and of the by-products of the fully decomposed molecules were also examined. Also, the electrochemical experimental results obtained under aerobic atmosphere were numerically fitted to model the production of NO and its degradation through its oxidation by molecular oxygen. All these information gathered together allows in predicting the real amount of NO released under real aerobic conditions.     

The homologous tert-amino effect: a route to fused 2-benzazepine derivatives

2-Cyano- and 2-carbethoxy-3-[2-(pyrrolidin-1-ylmethyl)phenyl]acrylonitriles were prepared through either amination of appropriate 3-[2-(bromomethyl)phenyl]acrylonitriles with pyrrolidine or condensation of 2-(pyrrolidin-1-ylmethyl)benzaldehyde with malononitrile and ethyl cyanoacetate. These acrylonitrile derivatives were shown to undergo easy mutual interconversion with 1-(pyrrolidin-1-yl)indane-2-carbonitriles driven by solvent polarity. Upon heating at 140-150 °C both acrylonitrile and indane derivatives were found to give 2,3,5,10,11,11a-hexahydro-1H-pyrrolo[1,2-b][2]benzazepine-11-carbonitriles. All transformations observed were rationalized in the terms of reactions related to the tert-amino effect. Furthermore, the corresponding piperidin-1-yl and azepan-1-yl analogs of the above acrylonitriles and indanes were obtained similarly. By analogy their heating afforded 1,2,3,4,6,11,12,12a-octahydropyrido[1,2-b][2]benzazepine-12-carbonitriles and 7,8,9,10,11,11a, 12,13-octahydro-5H-azepino[1,2-b][2]benzazepine-12-carbonitriles.     

A facile and convenient synthesis of novel imidazo[1,2-b] isoxazoles and their Mannich bases as potential biodynamic agents

A series of novel imidazo[1,2-b]isoxazoles 3 and their Mannich bases 4–6 were synthesized via convenient reactions. The reaction of 3-aminoisoxazole 1 with substituted phenacyl bromides 2 in dry ethanol afforded the corresponding 6-methyl-3-aryl imidazo[1,2-b]isoxazoles 3 in good yields.Compounds 3 on treatment with 37% formaline and secondary amines furnished the corresponding novel Mannich bases viz., 6-methyl-3-aryl-2-(morpholine/pyrrolidin-1-yl/piperidin-1-yl)-methyl-imidazo[1,2-b]isoxazoles 4–6.     

Nitric oxide modulates tumor cell death induced by photodynamic therapy through a cGMP-dependent mechanism

Photodynamic therapy (PDT) of cancer is a very promising technique based on the formation of singlet oxygen induced by a sensitizer after irradiation with visible light. The stimulation of tumor growth by nitric oxide (NO) was reported recently, and NO was shown to have a protective effect against PDT-induced tumor death. We investigated a putative direct effect of NO on tumor cell death induced by PDT, using the human lymphoblastoid CCRF-CEM cells and bisulfonated aluminum phthalocyanine (AlPcS2) as a sensitizer. Cells were incubated with AlPcS2 in the presence or absence of NO donors ((Z)-1-[(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate, hydroxylamine and S-nitroso-N-acetylpenicillamine) or L-arginine. Under these conditions, in the absence of NO donors or L-arginine the cells died rapidly by apoptosis upon photosensitization. In the presence of NO donors or L-arginine, apoptotic cell death after photosensitization was significantly decreased. Modulation of cell death by NO was not due to S-nitrosylation of caspases and occurred at the level or upstream of caspase-9 processing. The protective effect of NO was reversed by incubating the cells with 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, an inhibitor of guanylyl cyclase, or with KT5823, an inhibitor of protein kinase G (PKG). Incubation with 8-bromo-cyclic guanosine monophosphate, a membrane permeable cyclic guanosine monophosphate analog, also decreased cell death induced by PDT. Although the protective effect of NO against apoptotic cell death in several models has been attributed to an increase in the expression of heme oxygenase-1, heat shock protein 70 or Bcl-2, this was not the case under our experimental conditions. These results show that NO decreases the extent of apoptotic cell death after PDT treatment through a PKG-dependent mechanism, upstream or at the level of caspase activation.     

An improved synthesis of V-PROLI/NO, a cytochrome P450-activated nitric oxide prodrug

An improved synthesis of V-PROLI/NO, a cytochrome P450-activated nitric oxide (NO) prodrug, in an overall yield of 26% in four steps from prolinol is reported; the previously published yield of this transformation was 1%. Using this revised strategy, the sarcosine analogue (14) of V-PROLI/NO was prepared. Finally, the methyl ester of V-PROLI/NO (15) was found to be an esterase-activated prodrug form of V-PROLI/NO.     

抗丙肝药物维拉帕维的合成

以7-羟甲基-1-四氢萘酮和1-溴-4-氯-苯甲醛为起始原料,经14步反应合成了抗丙肝新药维拉帕维--甲基（2S）-1-【(2S,5S)-2-【9{2［（2S,4S）-1-（2R)-2-［（甲氧基羰基）氨基］-2-苯乙酰基-4-（甲氧基甲基）吡咯烷-2-基］-1H-咪唑 5 基} 1,11-二氢异色烯［4′,3′ :6,7］萘并［1,2-d］咪唑-2-基-5-甲基吡咯烷-1-基】-3-甲基-1-氧丁烷-2-基】氨基甲酸酯,总产率10.14%,其结构经¹H NMR和ESI-MS确证。     

Photochemistry of 1-(N,N-diethylamino)diazen-1-ium-1,2-diolate: an experimental and computational investigation

The aqueous photochemistry of the sodium salt of 1-(N,N-diethylamino)-diazen-1-ium-1,2-diolate (3) has been investigated by both experimental and computational methods. Photolysis results in the formation of the N-nitrosodiethylamine radical anion (5) and nitric oxide (NO) via a triplet excited state. The nitrosamine radical anion either undergoes electron transfer with NO before cage escape to form triplet NO(-) and nitrosamine (minor process) or rapidly dissociates to form an additional molecule of NO and ultimately amine (major process). The production of nitrosamine radical anion 5 upon photolysis of diazeniumdiolate 3 is confirmed by low-temperature EPR spectroscopy. The calculated energetics for the ground and excited states of the parent diazeniumdiolate ion at the CIS and B3LYP levels of theory as well as B3LYP calculations on the fragmentation processes were very effective in rationalizing the observed photodissociation processes.     

Cyclohexadienone diazeniumdiolates from nitric oxide addition to phenolates

Sterically hindered phenols react with nitric oxide under basic condititons to give either cyclohexadienone diazeniumdiolates or oximates. Phenols with 2,6-di-tert-butyl and 4-methyl (butylated hydroxy toluene, BHT), 4-ethyl, or 4-methoxy methylene substituents yield the corresponding 2,6-di-tert-butyl-2, 5-cyclohexadienone-4-alkyl-4-diazeniumdiolate salts (4-methyl 1a, 4-ethyl 3a, 4-methoxymethylene 5a). Phenols with 2,6-di-tert-butyl and 4-methylene (2,6-di-tert-butylphenol) substituents yield 4-methoxymethylenediazeniumdiolate (5a) together with 2, 6-di-tert-butyl benzoquinone oximate (6a), while phenols with 2, 6-di-tert-butyl and 4-methylenedimethylamino or hydrogen substituents yield exclusively 2,6-di-tert-butyl benzoquinone oximate (6a). Alkylation of the silver salts of 1a, or treating the O(2)-protonated diazeniumdiolate with diazomethane, both yield mixtures of O(1)- and O(2)-methylated isomers. All the compounds exhibit exothermic thermal decomposition except the quinuclidinium (1e, 3e, 5e) and triethylenediammonium (1f) salts which decompose endothermically. Three of the compounds namely "O(2)-protonated" (Z)-1-[4-(2, 6-di-tert-butyl-4-methyl-cyclohexadienonyl)]diazen-1-ium+ ++-1, 2-diolinic acid (1b), O(2)-methyl (Z)-1-[4-(2, 6-di-tert-butyl-4-methyl-cyclohexadienonyl)]diazen-1-ium+ ++-1,2-diolate (1c), and "O(2)-protonated" (Z)-1-[4-(2, 6-di-tert-butyl-4-methoxymethylenecyclohexadienonyl)]diazen- 1-ium-1, 2-diolinic acid (5b) were characterized by single-crystal X-ray diffraction studies. The diazeniumdiolate framework in all the structures is coplanar with considerable pi-bonding delocalized over the O-N-N-O framework.     

Bronsted acidic ionic liquid catalyzed an eco-friendly and efficient procedure for synthesis of 2,4,5-trisubstituted imidazole derivatives under ultrasound irradiation and optimal conditions

Research on Chemical Intermediates - 2-[(1H-imidazol-3-ium-3-yl)methyl]-4-{bis[3-((1H-imidazol-3-ium-3-yl) methyl-(4-hydroxyphenyl]methylene}cyclohexa-2,5-dienone trihydrogen sulfate...     

O2-(N-hydroxy(methoxy)-2-ethanesulfonamido) protected diazen-1-ium-1,2-diolates: nitric oxide release via a base-induced β-elimination cleavage

O(2)-(Ethanesulfohydroxamic acid) and O(2)-(N-methoxy-2-ethanesulfonylamido) diazen-1-ium-1,2-diolates (4-7), a novel type of O(2)-(protected) diazeniumdiolate, were synthesized using a key thioacetate oxidation reaction. Nitric oxide release studies showed that O(2)-(N-methoxy-2-ethanesulfonylamido) diazeniumdiolates 5 and 7 released NO in a nonphysiological alkaline buffer, in the presence of bases such as the basic natural amino acids Arg and His, or the non-nucleophilic organic base DBU in PBS at pH 7.4, via a β-elimination cleavage reaction.     

Topological variations of the PDP ligand and its prospects in molybdenum(0) dearomatization agents

The compounds fac-(κ(3)-PDP)Mo(CO)(3) {1; PDP = 2-[[2-(1-(pyridin-2-ylmethyl)pyrrolidin-2-yl)pyrrolidin-1-yl]methyl]pyridine}, [(cis-β-PDP)Mo(NO)(CO)]PF(6) ([cis-β-3]PF(6)), [(cis-α-PDP)Mo(NO)(CO)]PF(6) ([cis-α-3]PF(6)), [(cis-α-PDP)Mo(NO)Br]PF(6) ([4]PF(6)), [(trans-PDP)Cu](BF(4))(2)·CH(3)CN ([5](BF(4))(2)·CH(3)CN), and [(trans-PDP)Cu](OSO(2)CF(3))(2) ([5](OSO(2)CF(3))(2)) have been synthesized and structurally characterized by single-crystal X-ray diffraction. These are the first reported complexes of PDP on metal centers other than iron(II). The observed configurations indicate a broader range of accessible PDP topologies than has been reported. The {(cis-α-PDP)Mo(NO)}(+) fragment is found to be less π-basic than the dearomatizing {Tp(MeIm)Mo(NO)} fragment [Tp = hydridotris(1-pyrazolyl)borato; MeIm = 1-methylimidazole].     

Amine exchange reactions of 3-<Emphasis Type="Italic">tert</Emphasis>-butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide with amino acids

3-tert-Butyl-6-(methylsulfanyl)-1,2,3,4-tetrahydro-1,3,5-triazine hydroiodide enters into the amine exchange reaction with glycine and β-alanine in aqueous solution. The final exchange products are [4-(methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate and 3-[4-(methylsulfanyl)-5, 6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] propanoate, respectively, crystallizing together with t-butylamine hydroiodide from aqueous or aqueous alcoholic solutions as ion associates, which also can be detected in solution in DMSO-d ₆. [4-(Methylsulfanyl)-5,6-dihydro-1,3,5-triazin-3-ium-1(2H)-yl] acetate can be extracted directly from the reaction mixture after carrying out the amine exchange in aqueous isopropanol or 95% ethanol, as well as by “recrystallization“ of its associate with tert-butylamine hydroiodide from aqueous isopropanol.     

Carbene-mediated transformations of 1-(benzylideneamino)benzimidazoles

Carbene-mediated transformations of N-(3-butylbenzimidazol-3-ium-1-yl)-1-arylmethanimine iodides with carbon disulfide and benzoyl isothiocyanate gave the corresponding NHC·CS(2) betaines in 68-85% and benzoyl-[1-butyl-3-[(E)-(aryl)methyleneamino]benzimidazol-1-ium-2-carbothioyl]azanides, respectively, in 74-85% yields. However, reaction with excess isopropyl isothiocyanate in NaH/THF at room temperature yielded the 1-butyl-1',3'-diisopropyl-3-[(E)-(aryl)methyleneamino]spiro[benzimidazole-2,5'-imidazolidine]-2',4'-dithiones (74-77%).     

Greener synthesis using hydrogen peroxide in ethyl acetate of alicyclic ring-fused benzimidazoles and anti-tumour benzimidazolequinones

Environmentally-friendly and cost effective hydrogen peroxide in ethyl acetate was used to prepare in high yields pyrrolo[1,2-a]benzimidazoles from commercial o-(pyrrolidin-1-yl)anilines without the requirement for organic-aqueous extraction and chromatography. Six, seven and eight membered ring-fused analogues were similarly obtained in high yields with methanesulfonic acid required for the pyrido[1,2-a]benzimidazole. Anti-tumour benzimidazolequinone derivatives were obtained in high yield via the cyclization of 3,6-dimethoxy-2-(cycloamino)anilines.     

Synthesis,spectroscopic characterization,biological screening,and theoretical studies of organotin(IV) complexes of semicarbazone and thiosemicarbazones derived from (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone

Research on Chemical Intermediates - New organotin(IV) complexes of (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone thiosemicarbazone [L1H2], (2-hydroxyphenyl)(pyrrolidin-1-yl)methanone...