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In the current study, we reported the tandem synthesis of two series of arene-linked pyrimidinone hybrids with related fused thieno[2,3-b]pyridine moiety. The target hybrids were prepared, in moderate to excellent yields, by the reaction of a ternary mixture of the appropriate of 3-aminothieno[2,3-b]pyridine-2-carboxylate, DMF-DMA, and a series of aryl amines in dioxane at 110 [degrees]C for 8 h. The antibacterial activity of the new hybrids was estimated against six susceptible ATCC strains. Hybrids 5g and 7g, linked to a sulfonamide unit, showed the best efficacy against S. aureus and E. faecalis strains with minimum inhibitory concentration (MIC) values of 1.7-1.8 [micro]M, which exceed ciprofloxacin. Furthermore, some of new hybrids were examined as potential inhibitors of four different MRSA and VRE strains. Hybrids 5g and 7g demonstrated more potent efficacy than linezolid against MRSA strains with MIC values of 3.6/3.4 and 1.8/1.7 [micro]M against ATCC:33591 and ATCC:43300 strains, respectively. The prior hybrids displayed a comparable efficacy with linezolid against VRE strains with MIC values of 7.3/6.9 and 3.6/3.4 [micro]M against ATCC:51299 and ATCC:51575 strains, respectively. Additionally, some of the new hybrids were examined as potential COX-2 inhibitors using the reference celecoxib ([IC.sub.50] of 0.117 [micro]M). Hybrid 7g revealed more potent inhibitory efficacy than celecoxib with [IC.sub.50] of 0.112 [micro]M, whereas hybrid 5g showed almost inhibitory activity equivalent to celecoxib with [IC.sub.50] of 0.121 [micro]M. Molecular docking was performed to predict the possible binding interactions between hybrids 5g and 7g with the target COX-2 enzyme. Key words: COX-2 inhibitor, MRSA inhibitor, multi-component reaction, pyrido[3'2'45]thieno[32-d]pyrimidine, VRE inhibitor. La presente etude decrit la synthese en tandem de deux series d'hybrides de pyrimidinones liees a un arene dont la partie thieno[2,3b]pyridine est fusionnee. Nous avons prepare les hybrides cibles, avec des rendements moderes a excellents, par reaction d'un melange ternaire contenant le 3aminothieno[2,3b]pyridine-2carboxylate correspondant, du dimethylformamide-dimethylacetal (DMFDMA) et une serie d'arylamines dans le dioxane a 110 [degrees]C pendant 8 h. L'activite antibacterienne des nouveaux hybrides a ete evaluee contre six souches ATCC sensibles. Les hybrids 5g et 7g, lies a une unite sulfonamide, ont montre la meilleure efficacite contre les souches de S. aureus et E. faecalis, avec des concentrations minimales inhibitrices (CMI) de 1,7 a 1,8 [micro]M, ce qui surpasse l'efficacite de la ciprofloxacine. De plus, nous avons evalue certains des nouveaux hybrides comme possibles inhibiteurs de quatre souches differentes de SARM et d'ERV. Les hybrids 5g et 7g ont montre une meilleure efficacite que le linezolide contre les souches de SARM, avec des CMI de 3,6/3,4 [micro]M et de 1,8/1,7 [micro]M contre les souches ATCC:33591 et ATCC:43300, respectivement. Les hybrides anterieurs avaient montre une efficacite comparable a celle du linezolide contre les souches d'ERV, avec des CMI de 7,3/6,9 [micro]M et de 3,6/3,4 [micro]M contre les souches ATCC:51299 et ATCC:51575, respectivement. De plus, nous avons evalue certains des nouveaux hybrides comme possibles inhibiteurs de la COX2 en utilisant le celecoxib comme reference ([CI.sub.50] de 0,117 [micro]M). L'hybride 7g s'est revele etre un inhibiteur plus puissant que le celecoxib, sa [CI.sub.50] etant de 0,112 [micro]M, tandis que l'hybride 5g a montre une activite inhibitrice presque equivalente a celle du celecoxib, avec une [CI.sub.50] de 0,121 [micro]M. Nous avons soumis les hybrids 5g et 7g auneexperience d'amarrage moleculaire afin de predire leurs eventuelles interactions de liaison avec l'enzyme COX2 cible. [Traduit par la Redaction] Mots-cles : inhibiteur de COX2, inhibiteur de SARM, reaction a composants multiples, pyrido[3',2'4,5]thieno[3,2d]pyrimidine, inhibiteur d'ERV., Introduction The worldwide threat to current antibiotics of antimicrobial resistance has grown in recent years. (1-4) Globally, antimicrobial resistance is estimated to cause more than 700 thousand deaths per year. [...]

A series of new π-conjugated donor (D) and acceptor (A) dyad comonomers were prepared using Suzuki coupling protocols. The D-A comonomers consisling of thiophene/bilhiophene as donors and pyridine/pyrimidine as acceptors were prepared 10 investigate their photophysical and electrochemical properties. The dyads were spectroscopically confirmed to be highly conjugated. This was further supported by the X-ray crystal structure of the bithophene-pyridine dyad that showed all the heterocycles to be coplanar. It was further found that the fluorescence yields (On) of the dyads were highly dependent on the number of thiophenes. The bithiophene derivatives exhibited [Φ.sub.n] values ≥ 0.3 while the thiophene derivatives did not fluoresce. The suppressed fluorescence observed for the thiophene derivatives was due to their higher triplet energy resulting in efficient intersystem crossing (ISC) to the triplet state with [Φ.sub.ISC] ≥ 0.8. This was confirmed both by time-resolved and steady-state measurements. The singlet excited state of both thiophene and bithiophene dyads was deactivated solely by either fluorescence and (or) ISC. Owing to their donor and acceptor character, the dyads could be oxidized and reduced both electrochemically and photochemitally to afford the radical cation and anion, respectively. Key words: comonomer, thiophene, pyridine, pyrimidine. photophysics, fluorescence. A l'aide d'un couplage de Suzuki, une serie de comonomeres conjugues contenant une fonction donneur d'electrons (D) et une fonction accepteur d'electrons (A) out ete prepares. Ces comonomeres, dits D-A, qui utilisent le thiophene/bithiophene comme donneurs d'electrons et la pyridine/pyrimidine comme accepteurs d'electrons, ont ete synthetises dans le but d'analyser leurs proprietes photophysiques et electrochimiques. 11 a ete lvalue spectroscopiquement que les dimeres sont grandement conjugues. Ceci est d'ailleurs soutenu par la structure rayons-X du compose bithiophenepyridine qui montre que tons les heterocycles sont coplanaires. II a ete determine que les rendements quantiques de fluorescence ([Φ.sub.n]) des composes dependent du nombre de thiophenes presents dans la molecule. En effet, les derives du bithiophene ont des [Φ.sub.n] ≥ 0,3 tandis que les derives du thiophene ne fluorescent pas. Cette absence de fluorescence est causee par la formation d'un etat triplet de haute energie par croisement iutersysteme (ISC pour << intersystem crossing >>) avec un [Φ.sub.ISC] ≥ 0,8. L'etat singulet excite des dimeres de thiophene et de bithiophene est uniquement desactive par la fluorescence ou le ISC. Grace a leur caracterislique donneur/accepteur, les comonomeres ont pu etre oxydes el reduits electrochimiquement et chimiquement aim de former le radical cation et le radical anion. Mots-cles: comonomere, thiophene, pyridine, pyrimidine, photophysique, fluorescence. [Traduit par la Redaction], Introduction Conjugated materials have attracted much attention because of their electrochemical and photophysical properties that are ideally suited for plastic electronics, including organic field effect transistor, (1-4) photovoltaics, (5,6) emitting [...]

The optimized deprotonation reaction of diazines by using a zinc diamide-lithium amide mixture is described. The main advantage of this method is the formation of relative stability of the organometallic species, where hydrogen-lithium exchange is performed at low temperature in order to prevent side nucleophilic addition while hydrogen-zinc exchange proceeds at room temperature or more.

A systematic study of the CH/[pi] interactions of methane with the purine and pyrimidine bases of nucleic acids and with the lateral chains of the four natural aromatic amino acids which showed two different kinds of clusters depending on number of CH bonds in the aromatic systems is presented.

The synthesis of five new meso-tetraarylporphyrins having pyridine, pyrimidine or nitrile groups extending tetragonally via alkynyl linkages from the para positions is presented. The radial extension is nearly double that of common porphyrins such as tetra-p-pyridylporphyrin and these extended porphyrins are used in the area of porous metal-organic frameworks.

An experimental and a theoretical study on hydrogen bonding between pyrimidine and water as the H-donor were carried out. The results show that in a binary mixture of Pd and water both their relative concentrations and their dynamic exchange is dependent upon the composition of the mixture.

The study employs several techniques and methodologies to investigate and analyze the free jet absorption millimeterwave spectrum of the gas phase 4-hydroxypyrimidine system that is in tautomeric equilibrium with two different ketonic forms. The analysis reveals that equilibrium normally shifts in favor of the keto form, as its stability with respect to the enolic form increases with the number of ring nitrogen atom.

Ab initio surface-hopping dynamics was used to investigate the reaction path for the ultrafast deactivation of 6-aminopyrimidine (6AP). The electronic structure of the crossing seam was observed to have the same nature as those of simple biradicaloid systems, a feature which seems to be valid for any cyclic system.

Quantum chemical calculations were used to explore the mechanism employed by DNA photolyase to repair 6-4 photoproducts in ultraviolet (UV)-damaged DNA. A significant increase in the free-energy barrier for the initial fragmentation step upon protonation of the carboxylic oxygens is predicted from calculations on neutral azetidine radicals.

Density functional theory and ab initio methods are used to study the mechanisms for the hydrolysis of N-(2-oxo-1,2-dihydro-pyrimidinyl) formamide (PFA) in the gas phase. The results have shown that the solvent water slightly reduces the energy barrier in each pathway, but the first pathway in the water-assisted hydrolysis has remained the most favorable when the solvent effects of bulk water are taken into account.

Studies conducted on the molecular modeling and molecular dynamics (MD) simulations of the 4-hydroxyequilenin (4-OHEN)-A adducts in DNA 11-mer duplexes are presented. Similar stereochemical principles govern the orientations in DNA duplexes of the 4-OHEN-A adducts as for the analogous C adducts, with opposite orientations of the equilenin rings in stereoisomeric pairs of adducts characterized by near-mirror image circular dichroism (CD) spectra.

The high-level CASPT2//CASSCF quantum chemical techniques and ANO-type basis sets are applied to analyze the low-lying singlet states of the three pyrimidine DNA and RNA nucleobases uracil, thymine and cytosine. The analysis attempts to present a single view to elucidate the main photochemical events in the three systems after light irradiation, such as the measured ultrafast sub-picosecond decay and the origin of the low quantum yield fluorescence.

The infrared Raman spectroscopy and quantum chemical calculations were used to analyze the tautomerism and dimerization of 4(3H)-pyrimidinone (4(3H) Pyr) in carbon tetrachloride (C[Cl.sub.4]) and chloroform (CH[Cl.sub.3]) solutions. The outcomes point that keto enol tautomerization does not occur in the isolated monomer molecule and that the double proton transfer (DPT) reaction has a significant effect in the population increase of the enol form seen at high temperatures.

The characteristics as a chemosensor of the compound 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-d]pyrimidine are studied. It is seen that the Interaction with [Cu.sup.2} produces a quenching of the fluorenscence, while interaction with [Zn.sup.2} leads to quenching of the fluorescence followed by a bathochromic shift.

An addition-elimination process involving the reaction of appropriate organolithium derivatives and hexafluoropropene at low temperature results in the synthesis of various pentafluoropropenyl derivatives of pyrimidine and purine bases. The methodology is helpful in the quick and convenient synthesis of a series of perfluorovinyl nucleobases.

The molecular dynamics simulations were used to identify and characterize potential hydrogen bonding pathways that could facilitate the redox reaction catalyzed by human Dihydroorotate Dehydrogenase (DHOD). The mutation is found to increase the average donor-acceptor distances for proton and hydride transfer and to disrupt the hyrogen bonding pathways observed for the wild-type enzyme.

A model of the wild type B. st. formamidopyrimidine glycosylate (Fpg)-DNA duplex containing anti 8-oxoguanine (8OG) was built by using crystal structure of the complex with syn 80G and rotating the 8OG glycosidic bond. Subsequent unrestrained molecular dynamics simulations revealed that that the binding site can readily accommodate both anti and syn 8OG without significantly changing its conformation.

A synthesis of novel cations 14-substituted 1,3-dimethyl-5-10-methanocycloundeca[4,5]pyrrolo[2,3-d]pyrimidine-2,4-(1,3H)-dinoylium tetrafluoroborates 11a,b(super +).BF(sub 4)- which are catacondensed with pyrrolo[2,3-d]pyrimidine-1,2(2,4H)-dione toward 7(super +) was accomplished. The stability of cations 11a,b(super +) is expressed by the pK(sub R+) values which were determined spectrophotometrically as 9.8 ad 9.7, respectively.

A report is presented on simple, highly selective, neutral, fluorescent sensor for fluoride anions. It is based on 2-ureido-4(1H)-pyrimidinone quadruple hydrogen-bonded AADD (where A=acceptor of the hydrogen bonding, D=donor of the hydrogen bonding) supramolecular assembly and its assembling and disassembling processes are also able to respond to external stimuli reversibly.

A comparative study of the palladium-catalyzed arylation and heteroarylation of 5-bromoazolopyrimidines shows that aryl and electron-rich heteroaryl boronic acids gave higher yields than those obtained using the corresponding aryl and heteroaryl tributyl stannes. In contrast, the reaction with electron-poor heteroaryl tributyl stannanes gave better results than the corresponding boronic acids.

An enantioselective first total synthesis and structural revision of the cytotoxic natural product amphidinolide W is described. Optical rotation of amphidinolide W is reported for the first time after total synthesis and amphidinolide W and its diastereomers are very unstable and prone to decomposition even when they are stored at low temperatures.

A convenient and efficient synthesis of highly functionalized dihydropyrido[2,3-d]pyrimidines through a double [5 + 1] annulation strategy starting from easily available alpha-alkenoyl-alpha-carbamoyl kenete-(S,S)-acetals and cheap reagents are developed. The readily available substrates, cheap reagents, short steps, and mild reaction conditions, make this novel double [5 + 1] annulation strategy attractive and practical.

An efficient methodology for the synthesis of 4-phenylthiopyrimido[4,5-b][1,4]benzothiazepines was developed. This transformation can be rationalized by a mechanism similar to the Bischler-Napieralski-type reaction and the aryl sulfide group of the resulting 4-arylthiopyrimido[4,5-b][1,4]benzothiazepines can be subjected to selective oxidation and subsequent nucleophilic substitution.

A convenient, single-step synthesis of 2-amino-7-chlorothiazolo[5,4-d] pyrimidines directly from commercially available 5-amino-4,6-dichloropyrimidine and isothiocyanates under mild conditions is discussed. A set of novel, bivalent thiazolo[5,4-d] pyrimidine-2,7- diamines is prepared which are being investigated for biological utilities.

The introduction of an optically active N-substituent in the amide of 1-alkylated 1,4-dihydornicotinamides that can induce a modest to moderate chirality transfer toward carbonyl compounds is discussed. The reduction of a pyruvate analogue and some carbonyl compounds with the hydride-adduct was accomplished for the first time to give the corresponding alcohol derivatives.

A variety of 5-chloro-2(H)-1,4-oxazin-2-ones bearing a range of substituents at their 3- and 6-position undergo Diels-Alder cycloaddition as a 2-azadine component with electron-rich, electron-deficient and electron-neutral dienophiles. These reactions proceed with moderate regio and stereoselectivity to afford relatively stable and readily isolable bridged bicyclic lactone cycloadducts.

The ultrafast radiationless decay of photoexcited uracil and cytosine is investigated by ab initio quantum chemical methods based on CIS and CR-EOM-CCSD (T) electronic energy calculations at optimized CIS geometries. The investigation showed that, the three-state nonradiative decay mechanism, involving the intermediacy of a biradical state, satisfactorily accounts for the ultrafast radiationless decay of unmodified pyrimidine bases.

The electrochemical oxidation of a Hg electrode in the presence of thiopyrimidine derivatives has been investigated in a collection of organic solvents using voltammetric and polarographic techniques. Remarkable adsorption phenomena control the electrochemical process, which in all cases gives rise to a Hg(I) complex. The Laviron adsorption model is found to describe well the polarographic adsorption wave. Some correlations between adsorption parameters and solvent properties have also been observed and discussed. Key words: polarography, voltammetry, thiopyrimidine, solvent effect, adsorption. Resume : On a etudie l'oxydation electrochimique d'une electrode de mercure en presence de derives thiopyrimidines dans divers solvants organiques, en faisant appel a des techniques polarographiques et voltamperometriques. Un phenomene remarquable d'adsorption controle le processus electrochimique qui, dans tousles cas donne lieu a un complexe Hg(I). On a trouve que le modele d'adsorption de Laviron decrit bien la vague d'adsorption polarographique. On a observe et on discute de quelques corre1ations entre les parametres d'adsorption et les proprietes du solvant. Mots cles : polarographie, voltamperometrie, thiopyrimidine, effet de solvant, adsorption.

A systematic study of the synthesis of the 5,7-diaryl-4-oxo-pyrazolo [3,4-d]pyrimidin-6-thiones (3), 2-phenyl5,7-bis(2'-methylphenyl)-4-oxo-pyrazolo[3,4-d]pyrimidin-6-thiones (4b), 2(3H)-3-phenyl-5,7-diaryl-4-oxo-pyrazolo[3,4d]pyrimidin-6-thiones (5), 5,7-diaryl-4-oxo-isoxazolo[5,4-d]pyrimidin-6-thiones (7), 3,5,7-triaryl-2,3-dihydro-4-oxoisoxazalo [5,4-d]pyrimidin-6-thiones (8), 2-amino-6,8-diaryl-5-oxo-pyrimido[4,5-d]pyrimidin-7-thiones (9), 3,4-dihydro-2-amino-4-phenyl-6,8-diaryl-5-oxo-pyrimido [4,5-d]pyrimidin-7-thiones (10), 3-cyano-6,8-diaryl-2,5-dioxo-pyrido[2,3d]pyrimidin-7-thiones (11) from the condensation products 1 and 2, derived from 1,3-diaryl-2-thiobarbituric acids is described. Key words: synthesis, fused, pyrazole, isoxazole, pyrimidines. Resume : On decrit une etude systematique de la synthese des 5,7-diaryl-4-oxo-pyrazolo [3,4-d]pyrimidin-6-thiones (3), 2-phenyl-5,7-bis(2'-methylphenyl)-4-oxo-pyrazolo[3,4-d]pyrimidin-6-thiones (4b), 2(3H)-3-phenyl-5,7-diaryl-4-oxopyrazolo[3,4-d]pyrimidin-6-thiones (5), 5,7-diaryl-4-oxo-isoxazolo[5,4-d]pyrimidin-6-thiones (7), 3,5,7-triaryl-2,3dihydro-4-oxo-isoxazolo[5,4-d]pyrimidin-6-thiones (8), 2-amino-6,8-diaryl-5-oxo-pyrimido[4,5-d]pyrimidin-7-thiones (9), 3-4-dihydro-2-amino-4-phenyl-6,8-diaryl-5-oxo-pyrimid [4,5-d]pyrimidin-7-thiones (10) et 3-cyano-6,8-diaryl-2,5-dioxopyrido [2,3-d]pyrimidin-7-thiones (11) a partir des produits de condensation 1 et 2 obtenus a partir des acides 1,3-diaryl-2-thiobarbituriques. Mots cles : synthese, condense, pyrazole, isoxazole, pyrimides.

4-Aryl-6-methyl-3,4-dihydro-2(1H)-pyrimidinone esters (DHPMs) readily undergo metalation at the C-6 methyl position on treatment with lithium diisopropylamide at -10 degree Celsius. The resulting anion intermediates could be treated with electrophilic reagents to afford functionalized DHPMs that are chemically elaborated mainly at the C-6 position.

A practical synthesis of 2-[3-(4-fluoro-3-pyridin-3-yl-phenyl)-imidazo[1,2-alpha]pyrimidin-7-yl]-propan-2-ol, an oral GABA(sub A) alpha2/3-selective agonist is described. Consecutive Pd-catalyzed coupling steps to assemble the final free base in high yield and regioselectivity highlight the synthesis.

A novel, short and efficient synthetic pathway to 3-{4-[2-(3-chlorophenylamino)-pyrimidine-4-yl]-pyridin-2-ylamino}-propanol and a series of analogues is developed. The synthetic sequence consisted of a Negishi-type cross-coupling reaction in the key step followed by two subsequent nucleophilic substitution reactions.

An efficient synthesis of substituted azolopyrimidines such as [3', 2':4,5]pyrrolo[1,2-c]pyrimidines, pyrimido[1,6-a]indoles, benzo[4,5]imidazo-[1,2-c]pyrimidines, an imidazo-[1,2-c]pyrimidine, and pyrazolo[1,5-c]pyrimidines is described. The method is only successful under phase-transfer conditions (CH2Cl2/30% aq NaOH) using benzyltriethylmmonium chloride as a catalyst.

A mild and potentially general protocol is developed for the construction of polycyclic pyrazol[3,4-d]pyrimidines in a highly efficient manner. In addition to the high chemical efficiency, this route should be compatible with peripheral variation that will allow access to a library of compounds suitable for biological study.

A report is presented on the synthesis, solution-binding properties, and polymerization of 6-substituted 2,4-bis(acrylamido)pyrimidines for the imprinting of 1-benzyluracil (BU). Optically responsive receptors toward imides based on 6-substituted 2,4-bis(acrylamido)pyrimidines are presented.

The synthetic approaches to ureidopyrimidinones possessing p-aminophenyl groups at C-6, and an alkyl or hydrophilic side chain at R(sub 2), as well as an azo-derivative, are described. The studies investigating the tautomeric distributions of the compounds prepared are also presented.

A general and selective methods for partial reduction of pyridine, pyrimidine, and pyrazine rings of various heteroaromatic compounds with bridgehead nitrogen via Birch reduction motif is reported. This method could serve as a new and effective tool for quick and easy access toward various partially reduced fused heterocyclic compounds.

The structures, energetics, and vibration frequencies of H2O:pyrimidine and 2H2O:pyrimidine in their ground and first-excited (n,pi*) states were studied, using analogous first-principles computational methods for both the ground and excited states of these complexes. It was found that the excited-state hydrogen bond in H2O:pyrimidine is very similar to the ground-state structure.

The properties of a class of modified nucleobases called fleximers, which are purine derivatives with the imidazole and pyrimidine rings separated by a single carbon-carbon bond are presented. It was found that separating the imidazole and pyrimidine rings with a single carbon-carbon bond leads to highly flexible molecules with respect to rotation about the fleximer bond, while maintaining the integrity of the hydrogen-bonding patterns and properties of the natural purines.

A novel synthesis of 1,3-dimethyl-5,10-methanocycloundeca[4,5]furo[2,3-d]pyrimidin-2,4(1,3H)-dionylium tetrafluoroborate [10(super +).BF4(super -)] was accomplished by the reaction of 3,8-methanol[11]-annulenone with dimethylbarbituric acid and following acidic cyclization, albeit in low yield. Remarkable structural characteristics were suggested on inspection of the spectral data and MO calculation, and it was clarified that the positive charge is largely localized at the C11.

Fapy.dG and Fapy.dA are biologically interesting lesions that readily anomerize in aqueous solution, an unusual property for nucleotides. Experiments suggest that Fapy.dG exists almost exclusively as its Beta-anomer, and that Beta-Fapy.dA is also the major stereoisomer present in duplex DNA.

The 1-propynylation at C5 of consecutive pyrimidines in DNA could enhance DNA:RNA hybrid stability at 37 degree Celsius by over 1 kcal/mol of substitution. The increased stability of the propynylated duplexes has been caused by preorganization of the propynylated single strand and different interactions in the double strand.

A mixture comprising two of Davis' self-assembled ionophores, Rebek's tennis ball and calixarene tetraurea capsule, Meijer's ureidopyrimidinone, Reinhoudt's calixarene bis(rosette), and two molecular chips in CDCI3 is prepared to address the question of whether self-sorting in designed systems is exceptional behavior or whether it is likely to become a more general phenomenon governing molecular recognition and self-assembly.

The combination of thiamin and benzaldehyde can produce benzoin, but destroys thiamin, which is due to the cleavage of the C-N bond between heterocycles. The destruction is caused from fragmentation of the conjugate of thiamin and benzaldehyde.

Research is done on the decomposition of 4-methylpyrimidine, which was examined behind reflected shock waves in a pressurized driver single-pulse shock tube over the temperature range 1160--1330 K at overall densities of ~3 x 10(super -5) mol/cm(super 3). In conclusion, a reaction scheme containing 33 species and 91 elementary reactions was constructed to account for the observed product distribution and an examination on the decomposition mechanism is presented.

Results of a study conducted suggest that the two C-nucleosides d2APy and d2APm, although similar structure, exhibit two different selectives based upon their pK(sub a) values, 6.8 and 3.3, respectively. The d2APy residue with a greater pK(sub a) value, even higher than dC(pK(sub a)=4.3) is more effective than dC in targeting dG-dC base particularly at slight basis pH value.

The EPR spectrum of 2-pyrimidylnitrene (D=1.15 cm (super -1)) in its triplet ground state is produced by the photolysis (254 nm) of 2-azidopyrimidine (AP) in glassy ethanol (EtOH) at 77 K. Photolysis (254 nm) of AP in ethanol at 77 K leads to bleaching of the absorption of the azide (lambda(sub max) = 242 nm) and formation of a broad absorption band between 300 and 400 nm and a highly structured band between 400 and 450 nm.

A study of the preparation and the physical properties of three complexes containing the bridging ligand 5-(2-(4-pyridyl)ethyl)-2(2-pyridyl)pyrimidine (pypm-py) are described. The results show that energy transfer occurs between the Re(phen) chromophore and the Re(pypm) center in the bimetallic complex.

Research is done on the surface enhanced Raman scattering of 1,10-phenanthroline adsorbed on silver sol which has been obtained and analyzed by using normal mode calculations based on a valence force field suitably determined for this molecule. The similarity between SERS and normal Raman spectra of the corresponding 1:2 Ag (I)-phenathroline complex indicates that the molecule is perturbed upon adsorption as well as upon coordination in the argentous complex.