Collisionally activated dissociation of protonated 2′-deoxycytidine, 2′-deoxyuridine, and their oxidatively damaged derivatives

We examined the collisionally activated dissociation (CAD) pathways of protonated 2'-deoxycytidine (dC), 5-formyl-2'-deoxycytidine (5-FmdC), 5-hydroxy-2'-deoxycytidine (5-OHdC), 5-hydroxymethyl-2'-deoxycytidine (5-HmdC), and their corresponding stable isotope-labeled compounds to gain insights into the effects of modifications on the fragmentation pathways of the pyrimidine bases. Multi-stage MS (MSn) results showed that protonated cytosine, its 5-hydroxyl- and 5-hydroxymethyl-substituted derivatives, but not its 5-formyl-substituted analog, could undergo Dimroth-like rearrangement in the gas-phase. The elimination of HNCO was one of the major fragmentation pathways observed for the protonated ions of all dC derivatives except for 5-hydroxymethylcytosine, which underwent this loss only after a H2O molecule had been eliminated. In addition, the protonated cytosine and 5-hydroxycytosine can undergo a facile elimination of NH3 molecule. This loss, however, was not observed for protonated 5-hydroxymethylcytosine, 5-formylcytosine, and their uracil analogs. Taken together, our study demonstrated that modifications could alter markedly the CAD patterns of the protonated pyrimidine bases. The results from this study provided a basis for the identifications of other modified pyrimidine bases/nucleosides by tandem mass spectrometry.     

Synthesis and1H,13C,and29Si spectroscopic investigation of 2-thienyl(2′-Furyl)- and 2′-thienyl[2′-(4′,5′-dihydrofuryl)]silanes

The complete series of 2-thienyl(2-furyl)- and 2-thienyl[2-(4,5-dihydrofuryl)]silanes have been synthesized, and the influence of the character and number of substituents on the chemical shifts in the¹H,¹³C, and²⁹Si spectra has been investigated.DeceasedTranslated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1220–1225, September, 1995.     

Complexes of palladium,platinum and rhodium with 2,2′-biquinoline and 2-(2′-pyridyl)quinoline

Summary The reactions of 2,2-biquinoline(biq) with M(PhCN)₂X₂ (M=Pd; X=Cl or Br; M=Pt, X=Cl, Br or I), K₂PtCl₄ and RhCl₃·3H₂O and of 2-(2-pyridyl)quinoline (pq) with K₂PtCl₄ and RhCl₃·3H₂O have been investigated. The isolated complexescis-[Pd(biq)X₂] (X=Cl or Br),cis-[Pt(biq)Cl₂],cis-[Pt(biq)Cl₂]·H₂O,trans-[Pt(biq)₂Br₂]·5H₂O, [Pt₃(biq)₂I₆],mer-[Rh(biq)Cl₃-(H₂O)] andmer-[Rh(pq)Cl₃(H₂O)] have been characterized by elemental analyses, conductivity measurements, i.r., electronic, and¹H n.m.r. spectra. The reaction of pq with K₂PtCl₄ in 1M H₂SO₄ gave the salt 2-(2-pyridyl) quinolinium tetrachloroplatinate(II) pentahydrate, (pqH)₂[PtCl₄]·5H₂O; when the reaction was carried out in aqueous acetone,cis-[Pt(pq)Cl₂] was obtained. A new method for the synthesis ofcis-[Rh(biq)₂X₂]X (X=Cl or Br) is described; both compounds have been further characterized by¹H n.m.r.     

Synthesis of 5,5′-Dialkyl-6,6′-dichloro-2, 2′-bipyridines

5,5′-Dialkyl-6,6′-dichloro-2,2′-bipyridines were synthesized starting from 3-substituted 2-chloro-6-iodopyridines using Pd-catalyzed coupling conditions. 6-Alkyl-3,5-dichloro-2H-1,4-oxazin-2-ones were excellent precursors for the synthesis of these functionalized 2-iodo-6-chloropyridines.     

Syntheses, Characterization and Crystal Structures of Two-dimensional 4,4′-Bipyridyl Lead Halides, PbI_2(4,4′-bpy) and PbBr_2(4,4′-bpy)

IntroductionLinear bidentate N,N′- donor complexes havebeen extensively used in recent years to obtain thepolymeric frameworks with potential applicationprospects in different areas of material sciences,such as electrical conductivity[1] ,magnetism[2 ] ,photomechanical behaviour[3 ] and catalysis[4～ 6] .Among them,4,4′- bipyridine( bpy) has beenproven to be able to form one- dimensional poly-mers[7] ,two- dimensional layers[4] ,and three- di-mensional frameworks exhibiting the interpene-tra…     

Calorimetric study of 2′-methylacetophenone and 4′-methylacetophenone

Values of the condensed phase standard (p = 0.1 MPa) molar enthalpy of formation for 2′- and 4′-methylacetophenones were derived from the standard molar energies of combustion, in oxygen, at T = 298.15 K, measured by static bomb combustion calorimetry. The values of the standard molar enthalpy of vaporization, at T = 298.15 K, were measured by Calvet microcalorimetry. Combining these two values, the following enthalpies of formation in the gas phase, at T = 298.15 K, were then derived: 2′-methylacetophenone, –(115.7 ± 2.4) kJ · mol⁻¹, and 4′-methylacetophenone, –(122.6 ± 2.4) kJ · mol⁻¹. Substituent effects are discussed in terms of stability and compared with other similar compounds. The value of the standard molar enthalpy of formation for 3′-methylacetophenone was estimated from isomerization schemes.     

An Efficient Preparation of 4, 4′-Dicarboxy-2, 2′-Bipyridine

A convenient and high yield preparation of 4, 4′-dicarboxy-2, 2′-bipyridine from the oxidation 4, 4′-dimethyl-2, 2′-bipyridine with potassium dichromate in sulfuric acid is reported.     

Synthesis,Crystal Structure and Spectroscopic Properties of N,N′-Diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine

A fluorinated tetraphenylbenzidine derivative, N,N′-diphenyl-N,N′-bis(2-fluorophenyl)-1,1′-biphenyl-4,4′-diamine (C36H26F2N2, Mr = 524.59) was synthesized via the palladiumcatalyzed Buchwald-Hartwig reaction of N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine with 2-fluoroiodobenzene (yield: 75%) and structurally characterized. It crystallizes in monoclinic, space group P21/n with a = 9.820(7), b = 14.305(11), c = 10.233(8) , β = 108.973(9)o, V = 1359.3(18) 3, Z = 2, Dc = 1.282 g/cm3, μ(MoKα) = 0.084 mm-1, F(000) = 548, S = 1.018, the final R = 0.0439 and wR = 0.0928. It presents a linear centrosymmetric framework constituted by a linkage of biphenyl as a bridge and two fluorinated diphenylamine moieties. The UV-Vis absorption and fluorescence spectra of the title compound were also investigated. This compound emits intense blue fluorescence with a peak wavelength of 406 nm in film.     

Partial Protection of Carbohydrate Derivatives. Part 13.1 Chemical Conversion of Kanamycin A Into 2′-Deoxykanamycin A, 2′-Epi-Kanamycin A,and 2′-Epi-Kanamycin B

Abstract

Hydrazinolyses of hexa-0-benzoyl-tetra-N-benzyloxycarbonyl-and N-ethoxycarbonylkanamycin A were performed and found to be sufficiently regioselective to give the corresponding 2′-hydroxyl derivatives in good yields under controlled conditions. The products were converted into the corresponding 2′-triflates, which were then subjected to nucleophilic substitution reactions with sodium benzenethioxide, sodium benzoate, and sodium azide to give the corresponding d-mannopyranosyl derivatives in good yields. Deprotection of the phenylthio (10) and azido (12) derivatives, and hydrogenolysis, gave 2′-deoxykankmycin A and 2′-epi-kanamycin B, respectively. Moreover, deprotection of the benzoyl compound 11 gave 2′-epi-kanamycin A.     

Preparation of DNA duplexes containing 2′-fluoro-2′-deoxyuridine and arabinosyluracil

The synthesis of two 14-membered duplexes containing 2-fluoro-2-deoxyuridine and 1--D-arabinosyluracil, respectively., has been effected by chemical ligation (CL). During the synthesis of the first of them, it was observed that the ammonolysis of the completely blocked ACGGAU^2F was accompanied by the transformation of the modified unit into arabinouridine with the formation of 45% of ACGGAU^ara. It has been established that the introduction of an electron-accepting substituent adjacent to the reacting 3-OH group has no influence on a characteristic feature established previously: CL is considerably more effective if the reacting phosphate group is present at the 3-end, and not the 5-end, of the oligonucleotide.M. V. Lomonosov Moscow State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 263–267, March–April, 1991.     

Synthesis,spectroscopic characterization,thermal, and photostability studies of 2-(2′-hydroxy-5′-phenyl)-5-aminobenzotriazole complexes

Three Mn(II), Co(II), and Cu(II) new transition metal complexes of the fluorescence dye: 2-(2′-hydroxy-5′-phenyl)-5-aminobenzotriazole/PBT derived from o-aminophenol and m-phenylenediamine have been synthesized. The structural interpretations were confirmed from elemental analyses, magnetic susceptibility and molar conductivity, as well as from mass, IR, UV–Vis spectral studies. From the analytical, spectroscopic, and thermal data, the stoichiometry of the mentioned complexes was found to be 1:2 (metal:ligand). The molar conductance data revealed that all the metal chelates are non-electrolytes and the chloride ions exist inside the coordination sphere. The thermal stabilities of these complexes were studied by thermogravimetric (TG/DTG) and the decomposition steps of these three complexes are investigated. The kinetic parameters such as the energy of activation (E*), pre-exponential factor (A), activation entropy (ΔS*), activation enthalpy (ΔH*), and free energy of activation (ΔG*) have been reported. Photostability of phenyl benzotriazole as fluorescence dye and their metal complexes doped in polymethyl methacrylate/PMMA were exposed to UV–Vis radiation and the change in the absorption spectra was achieved at different times during irradiation period.     

Synthesis of 2′-deoxy-2′-fluororibo- and 2′-deoxy-2′,2′-difluororibonucleosides derived from 6-(het)aryl-7-deazapurines

A series of novel sugar-modified derivatives of cytostatic 6-hetaryl-7-deazapurine ribonucleosides (2′-deoxy-2′-fluororibo- and 2′-deoxy-2′,2-difluororibonucleosides) bearing an aryl or hetaryl group in position 6, was prepared and screened for biological activity. The fluororibo derivatives were prepared by aqueous palladium catalyzed cross-coupling reactions of the corresponding 6-chloro-7-deazapurine 2′-deoxy-2′-fluororibonucleoside 11 with (het)arylboronic acids. The key intermediate 11 was prepared by a six-step sequence from the corresponding arabinonucleoside by selective protection of 3′- and 5′-hydroxyls by acid-labile groups followed by stereoselective S_N2 fluorination and deprotection. The difluororibo-series was prepared by non-stereoselective glycosidation of 6-chloro-7-deazapurine with benzoyl-protected 2-deoxy-2,2-difluoro-d-erythro-pentofuranosyl-1-mesylate followed by cross-couplings, separation of anomers and deprotection. The title nucleosides did not show considerable cytostatic or antiviral activity.     

Synthesis of Phosphorylated Derivatives of Sucrose: 6,6′-di-Phosphonate, 6- and 6′-Phosphonates,and 6,6′-di-Phosphine

Reaction of 6,6′dideoxy-6,6′di-iodo-1′,2,3,3′,4,4′-hexa-O-benzylsucrose with triethyl phosphite afforded the corresponding 6,6′-diphosphonate. Selective phosphonylation either at the C-6 or 6-6′ position was also possible providing the corresponding sucrose mono-phosphonates. Reaction of 6,6′-dichloro-hexa-O-benzylsucrose with diphenylphoshine anion afforded the 6,6′-diphosphinosucrose.     

Cyclopalladated 2-phenyldihydrooxazole complexes with ethylenediamine, 2,2′-bipyridine,and bridging acetate ligands

The ¹H NMR, electronic absorption, and luminescence spectra, as well as voltammograms of the reduction and oxidation of the complexes [Pd(C∧N)(N∧N)]ClO₄ and [Pd(C∧N)(μ-OOCCH₃)]₂ [where (C∧N)⁻ is deprotonated 2-phenyl-4,5-dihydro-1,3-oxazole, and N∧N is ethylenediamine or 2,2′-bipyridine (bpy)] were compared. Magnetic nonequivalence of protons in the dihydrooxazole ring and upfield shift of the corresponding signals were observed as a result of anisotropic effect of the ring current in palladated phenyl substituents in the [Pd(C∧N)(μ-OOCCH₃)]₂ complex having a C ₂ symmetry. One-electron reduction wave of [Pd(C∧N)bpy]⁺ was assigned to ligand-centered electron transfer to the π* orbital of 2,2′-bipyridine, and two oxidation waves of [Pd(C∧N)(μ-OOCCH₃)]₂ were attributed to successive one-electron oxidations of the palladium centers. Low-temperature (77 K) phosphorescence of [Pd(C∧N)En]⁺ and [Pd(C∧N)bpy]⁺ was ascribed to optical transition localized on the metal-complex fragment {Pd(C∧N)} and to interligand charge transfer between the chelating and cyclopalladated ligands. The formation of metal-metal bond in the complex [Pd(C∧N)(μ-OOCCH3₎]₂ gives rise to radiative decay of photoexcitation energy from two electronically excited states, one of which is localized on the {Pd(C∧N)} fragment, and the second corresponds to the charge transfer metal-metal-cyclopalladated ligand.     

Efficient Preparative Rentes to 6,6′-Dibromo-2-2′-bipyridine and 6-Bromo-2,2′-bipyridine

The preparation of 6,6′-dibromo-2,2′-bipyridine and 6-bromo-2,2′-bipyridine are described. The dibromo compound was prepared by way of an improved cuprate synthesis resulting in a 72% yield. The monobromo species was prepared from the dibromo compound by way of metal-halogen exchange in 88% yield.     

Synthesis, Structure, Photoluminescence and Theoretical Study of (N,N′-Dimethyl-4,4′-bipyridinium)[Cd2(μ 2-Cl)4Cl2]n with N,N′-Dimethyl-4,4′-bipyridinium Generated in Situ

The title complex, (N,N′-dimethyl-4,4′-bipyridinium)[Cd₂(μ ₂-Cl)₄Cl₂]_n (1), in which the N,N′-dimethyl-4,4′-bipyridinium was generated in situ, was synthesized via hydrothermal reaction. X-Ray diffraction analysis revealed that the structure of 1 consisted of MV ²⁺ (MV ²⁺ = N,N′-dimethyl-4,4′-bipyridinium) cationic moieties and infinite [Cd2(μ ₂-Cl)₄Cl₂]_n anionic chains. The cadmium atom was bound by one terminal chlorine atom and four μ ₂-bridging chlorine atoms, yielding a slightly distorted triangular bipyramid. Photoluminescent investigation revealed that the complex displayed an emission in greenish blue region.     

Synthesis of 5′-benzoyl-2′-hydroxychalcones and related flavonoid compounds

Summary 5 -Benzoyl-2 -hydroxychalcones were synthesized by the condensation of 5 -benzoyl-2 -hydroxyacetophenone with aromatic aldehydes in presence of an ethanolic solution of potassium hydroxide. Derivatives of 6-benzoylflavonoids were prepared from chalcones.     

Synthesis of 5-substituted-3-[(2′S,3′S)-3′-hydroxy-2′-hydroxymethyltetrahydrofuran-3′-yl]-1,2,4-oxadiazoles and their epimers

5-Phenyl-3-[(2′R,3′S)-3′-hydroxy-2′-dimethoxymethyltetrahydrofuran-3′-yl]-1,2,4-oxadiazole 10a and its epimer 11a, 5-methyl-3-[(2′R,3′S)-3′-hydroxy-2′-dimethoxymethyltetrahydrofuran-3′-yl]-1,2,4-oxadiazole 10b and its epimer 11b were synthesized from cyanohydrin benzoates 8a, 9a and cyanohydrin acetates 8b, 9b, respectively, by treatment with hydroxylamine in methanol via intramolecular transacylation and subsequent cyclization of the corresponding amidoximes. Hydrolysis and reduction of the dimethoxymethyl groups in the above compounds gave the desired compounds 12a, 13a, 12b and 13b.     

A calorimetric study of N,N-diethyl-N′-furoylthiourea and N,N-diisobutyl-N′-furoylthiourea

The standard ( p^o =  0.1 MPa) molar enthalpies of combustion in oxygen, at T =  298.15 K, were measured by rotative bomb calorimetry for crystalline N, N -diethyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(C₂H₅)₂, HFET, and N, N -diisobutyl- N^′-furoylthiourea, (2-C₄H₃O)CONHCSN(iso-C₄H₉)₂, HFIB. The standard molar enthalpies of sublimation of both HFET and HFIB were measured by high-temperature Calvet microcalorimetry. These values were used to derive the standard molar enthalpies of formation of the compounds, in their crystalline and gaseous phases.     

Synthesis,resolution and application of 2,2′-bis(di-2-furylphosphino)-1,1′-binaphthalene

A six step synthesis and resolution of (±)-2,2′-bis(di-2-furylphosphino)-1,1′-binaphthalene 4 (TetFuBINAP) is described along with its use in asymmetric inter- and intramolecular Heck reactions.