The antibody-mediated hydrolysis of the nerve agent O-1,2,2-trimethylpropyl methylphosphonofluoridate (soman) 1 has now been established with two monoclonal antibodies raised against the cyclic pentacovalent methyloxyphosphorane hapten 10 that mimics the pentacoordinated trigonal bipyramidal transition-state of the reaction. The hydrolysis reaction was studied using molecular orbital methods at the MP2/6-31 + G*/(/)HF/6-31 + G* level of accuracy. According to the ab initio calculations, the reaction seems to proceed via three separate transition-states. The calculations are in good agreement with the experimental results. The 1,3-dioxabenzophosphole hapten 10 was synthesized, coupled to the carrier protein and the antibodies were obtained by the hybridoma technique. Two antibodies, DB-108P and DB-108Q were found to enhance the rate of soman hydrolysis and they were kinetically characterised.
2,2,2',2'-Tetrabromo-1-phenylbicyclopropyl and 1,1-dibromo-2-(2,2-dibromocyclopropyl)methyl-2-phenylcyclopropane have been synthesized, analyzed by X-ray crystallographic techniques, and exposed to acetone-sensitized irradiation. The former compound, which was obtained as a single diastereoisomer, gave a product mixture consisting of an undisclosed number of the corresponding tribromides resulting from reduction at either ring. The latter tetrabromide was separated into its diastereoisomers, which were irradiated separately. One of the diastereoisomers gave a mixture of tribromides caused by reduction at either ring, whereas the other isomer was reduced regioselectively at the phenyl-substituted ring and gave a mixture of cis- and trans-1-bromo-2-(2,2-dibromocyclopropyl) methyl-2-phenylcyclopropane.
The mechanistic study of trans-anethole oxidation at platinum electrodes by cyclic voltammetry in acetonitrile shows that reaction occurs by a rapid radical-radical dimerization of the trans-anethole radical cation. The use of the scanning electrochemical microscope (SECM) for studying homogeneous kinetics allowed the determination of the very large rate constant for the coupling between two trans-anethole radical cations: log(k/M-1 s(-1)) = 8.6+/-0.4. Combining this result with the cyclic voltammetric data allowed us to estimate the standard potential of the Irans-anethole radical cation as E degrees=1.40(4) V vs. SCE.
The new phosphoenols 1-6 and 9 have been synthesized starting from stable simple enols. Upon chemical or electrochemical oxidation, for the first time phosphoenol radical cations could be characterized in solution by cyclic voltammetry and EPR spectroscopy. The preparative one-electron oxidation of the model systems afforded the benzofurans indicating an unprecedented mesolytic P-O bond cleavage. Using cyclic voltammetry the kinetics of this step was determined in dichloromethane and acetonitrile. A rationale to account for the selectivity of the mesolytic P-O bond cleavage is given. Accordingly, reactive species P+(OEt)(2) (16) and P-.(=O)(OEt)(2) (18) can be generated selectively by mesolytic cleavage. At high scan rates, the partially reversible oxidation wave 1(.+)reversible arrow 1(++) could be monitored indicating that the dication of enol phosphate 1 is relatively stable.
The sixteen stereoisomers of 3,7,9-trimethyl-2-tridecyl acetate (5Ac) were prepared individually, each in over 99.5% stereochemical purity. The syntheses were based on the ring opening of a pure enantiomer of cis-3,4-dimethyl-gamma-butyrolactone using a pure stereoisomer of 1-lithio-2,4-dimethyloctane, the two stereogenic centres of which were introduced with high selectivity by alkylations of the amide enolates from the appropriate enantiomers of pseudoephedrine. (2S,3R,7R,9S)-3,7,9-Trimethyl-2-tridecyl acetate (SRRS-5Ac) has recently been found to be the major component of the female sex pheromone of Macrodiprion nemoralis (Hymenoptera: Diprionidae). A synthetic method for the preparation of a sixteen isomer mixture of 5Ac is also presented. This mixture has been found to be biologically active in field tests.
Aqueous carbonate complexes of Mn-II, Mn-III and Mn-IV were prepared and investigated by UV-visible spectrophotometry and electrochemical techniques. Mn-II forms soluble anionic carbonate complexes in concentrated carbonate solutions. A complex with two CO32- has been found in 1 M K-2 CO3 solutions. The value of its conditional formation constant is in the range 10(5.7 +/- 0.3). The soluble Mn-II carbonate complexes are readily oxidized by air to Mn-III species. Mn-IV complexes were obtained by reduction of MnO4- ions or by oxidation of Mn-II in concentrated carbonate solutions. Insoluble solids, probably oxides, were often produced during the studied oxidation-reduction reactions.
6,6'-Bis{methyl[1-(2-hydroxyethyl)piperazyl]}-2,2'-bipyridine was synthesized, and its complex formation equilibria with cobalt(II), nickel(II), copper(II) and zinc(II) ions were studied with potentiometric techniques over the pH range 2.2-9.6 in 0.10 mol dm(-3) NaCl at 25 degrees C. The data indicate the formation of the species [M(HXLY)]((2+X)+) (X = 0-3 and Y = 1, 2) and the hydrolysed [M(OH)(X)L]((2-X)+) complexes (X = 1, 2). All the metal ions formed the [M(H2L)](4+) complexes, but Co-II and Zn-II also formed the [M(H3L)](5+) complexes. The protonation of the ligand and the complex formation were studied by H-1 NMR at 24 degrees C as well as by UV-VIS spectroscopy at 25 degrees C. These spectroscopic data, together with potentiometric results, can be used to discuss the conformational changes between the [M(H3L)](5+) and the [M(H2L)](4+) complexes.
The substituted phthalonitriles 4-phenylphthalonitrile (2a), 4-(2,5-dimethoxyphenyl) phthalonitrile(2b) and 2-(3,4-dicyanophenyl)-4-methylpyridine(2c) have been prepared in good yields from 4-iodop ...
The preparation of two 1,4-diketones, and their subsequent Paal-Knorr reaction with various primary amines and amino acid derivatives to give the corresponding pyrroles, is described.
A bicyclic phenyldioxohexahydro-1H-isoindole-based hapten with a high similarity to the transition state of the ene reaction between maleimide and allylbenzenes has been designed and synthesized.
4,4'-Dimethoxytrityl and acetyl sugar protected alpha and beta thymidines are converted into the corresponding N-4-aryl-2-deoxy-5-methylcytidines via 4-(2,4,6-trimethylbenzenesulfonyloxy) pyrimidin-2(1H)-one nucleosides. These compounds were used for DNA synthesis after deacetylation and phosphitylation. Increased melting temperatures (6.2-9.6 degrees C) of three-way junctions (TWJ) were observed when N-4-(2-anilinophenyl)-, N-4-(2-benzylphenyl)- or N-4-(2-fluorenyl)-2-deoxy-5-methylcytidines were inserted into the middle of the junction region. A 26.6 degrees C increase in melting temperature was observed using a nucleosides in one of the strands of TWJ and with insertion of 2-deoxy-N-4-(2-fluorenyl)-5-methyl-alpha-cytidine at the junction. A large increase in thermal melting (18.8 degrees C) of the TWJ was also observed when 2-deoxy-5-methyl-N-4-(4-phenoxyphenyl)-alpha-cytidine was inserted at the junction as a chimeric nucleoside into a strand of beta nucleosides.
On the basis of an extensive on-line literature search a short review (with 50 references) is given of the preparative-scale synthetic chemistry of carbon monosulfide.
Two non-nucleosidic monomers conjugated to a phenoxyaniline intercalator have been synthesized and inserted into ODNs. The conjugated monomers were prepared from 2-chloro-N-(4-phenoxyphenyl) acetamide (1) either by reaction with diethanolamine and 4,4'-dimethoxytritylation, or by reaction with ethanolamine by subsequent peptide coupling type reaction with 4,4'-dimethoxytrityl protected glycolic acid. The modified ODNs moderately stabilize DNA three-way junctions when the intercalator was introduced at the branch point. For targeting RNA the results were more ambiguous.
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The strain energies in the five-membered rings 1,3,2-dioxathiolane (1), its 2-oxide (2) and 2,2-dioxide (3) have been evaluated using B3LYP and QCISD(T)//MP2 calculations and the standard 6-31G* basis set. Two different models have been used, one based on an isodesmic reaction involving methane and ethane, and one applying the chair-form of cyclohexane as a strain-free reference. Thermally corrected strain energies obtained by B3LYP and with cyclohexane as a reference are 10.1, -1.3 and 5.8 kcal mol(-1) for 1, 2 and 3, respectively. The corresponding values obtained by QCI calculations are 8.1, -2.1 and 4.4 kcal mol(-1), respectively. The negative value for 2 is interpreted in terms of absence of destabilizing interactions present in 1 and 3.
We describe how to selectively affect either beta-to-beta coupling (electrohydro-dimerization) or coupling between the alpha and beta centers of aliphatic nitroalkenes, the latter in a catalytic process that can be initiated both with and without electrochemistry. Of particular significance is our discovery of conditions that allow electrohydrodimerization to be conducted using aliphatic nitroalkenes bearing acidic protons. Thus, one can affect at will, either a catalytic alpha-to-beta coupling or an electrohydrodimerization using substrates that bear acidic protons, as well as those that do not. We also describe both voltammetric and ESR studies of the simple 1 -nitro-3,3-dimethyl-1-butene, as well as the results of quantum mechanical calculations that shed light upon the nature of radial anions derived from electron deficient olefins. Both calculation and experiment suggest: that the reluctance of these materials to undergo electrohydrodimerization can be correlated with the low electron density on carbon and the corresponding high value on oxygen, of the radical anion.
The 1,6- to 1,2-addition product ratios of the Grignard reactions of benzophenone with t-, s- and n-C4H9MgCl have been compared with the corresponding ratios obtained by the electrolysis of benzophenone in presence of t-, s- and n- C4H9S+(CH3)(2), ClO4- in THF. The Grignard reaction ratios 0.81, 0.50 and 0.19, respectively, were obtained whereas the corresponding electrolysis ratios were 2.26, 1.23 and 1.61. From this comparison of product ratios ii. is concluded that none of the Grignard reactions of benzophenone proceeds through a complete free coupling process of benzophenone radical anions and butyl radicals. The ET character of the Grignard reactions of benzophenone with t-, s- and n- C4H9MgCl was estimated to be 65, 61 and 26%, respectively.
