Synthesis of the 3-methyl and 4-methyl derivatives of 3-amino-3,4-dihydro-1-hydroxycarbostyril and related compounds

The 3-methyl and 4-methyl derivatives of 3-amino-3,4-dihydro-1-hydroxycarbostyril were synthesized by the reductive cyclization of α-methyl-β-(o-nitrophenyl)alanine and α-amino-β-(o-nitrophenyl)butyric acid hydrohalides, respectively, under conditions of catalytic hydrogenation in acidic solution. The free bases of the latter two o-nitroaromatic amino acids were also catalytically hydrogenated under neutral conditions to yield the respective α-methyl-β-(o-aminophenyl)alanine and α-amino-β-(o-aminophenyl)butyric acid which were converted to the corresponding lactams, 3-methyl- and 4-methyl-3-amino-3,4-dihydrocarbostyrils. α-Methyl-β-(o-nitrophenyl)alanine was obtained by acid hydrolysis of 5-methy)-5-(o-nitrobenzyl)hydantoin which was prepared by treatment of o-nitrophenylacetone with potassium cyanide and ammonium carbonate. α-Amino-β-(o-nitrophenyl)butyric acid was synthesized by condensation of α-bromo-o-nitroethylbenzene with diethyl acetamidomalonate, followed by acid hydrolysis of the condensation product. The 4-methylated compounds were obtained as synthetic mixtures of two diasteromeric racemates in nearly the same amounts as shown by nmr spectral analysis. Unlike the demethylated parent compound, 3-amino-3,4-dihydro-1-hydroxycarbostyril, neither the 3-methyl nor 4-methyl analog was found to possess any antibacterial activity.     

Cathodic reduction of nicotinamide adenine dinucleotide and other adenine-containing compounds in acidic media

Both nicotinamide adenine dinucleotide (NAD⁺) and acid-hydrated NADH, as well as adenine, adenosine, adenosine mono-, di-, and tri-phosphate and adenosine diphosphoribose, undergo four-electron reductions of the protonated adenine ring in acidic media. The values of αn_a (transfer coefficient times the number of electrons involved in the rate-determining step), n (total number of electron transferred), and p (number of protons involved in the rate-determining step) agree well with values previously reported for adenine. Cathodic stripping voltammetry of an adsorbed film can be applied to these compounds. Rapid scan rates are required to eliminate the slow desorption step at ?1.1 V vs. SCE for some of these compounds. Hydration of the nicotinamide ring of NADH appears to inhibit this desorption step, but does not appear to be related directly to the electroactivity of the hydration product.     

meso-tetrakis[2.2]paracyclophanylporphyrin: Electronic structure and electrochemical behavior

Replacement of all phenyl groups in meso-tetraphenylporphyrin, TPP, by [2.2]paracyclophane, PCP, enhances the increase of energy of the HOMO and HOMO-1 of porphine, P, already noticed for the mono-[2.2]paracyclophanyl-substituted TPP, and fills the energy gap by the occupied MOs of the PCP units. The first oxidation half-wave potential is respectively decreased to 0.52 V. The CNDO/S-CIS calculations agree with the experimental bathochromic shifts of all bands in the electronic spectra of the considered atropoisomers of the title compound, TPCPP, as compared to TPP. In the excited B states the interactions between the PCP and porphine units are represented mainly by the charge transfer of 0.44 e from PCP to P, according to transition density matrix calculations. While electroreduction of the title compound results in a successive formation of the anion radical and dianion, oxidation represents a four-step process involving one electron transfer per step, and resulting in the oxidation of two PCP units. Formation of the conductive polymeric film on the electrode seems to be connected with the transient formation of a quinoid system of bonds.     

Analysis of classes of compound of environmental concern: I. Nitroaromatic compounds

Thirty five nitroaromatic compounds (currently listed in EPA Method 8091) and 1,4-naphthoquinone have been separated on DB-5–DB-1701 and SPB-5–SPB-1701 column pairs, which were in each case connected to an inlet splitter and separate electron capture detectors. Retention times are included for 21 additional compounds evaluated for their suitability as internal standards and/or surrogate compounds for incorporation into Method 8091. Method reproducibility and linearity are discussed, and results are presented for extracts of two real samples spiked with the 35 nitroaromatic compounds and 1,4-naphthoquinone and analyzed using the dual-column-dual-detector arrangement.     

Substrate specificity for catalysis of phosphodiester cleavage by a dinuclear Zn(II) complex

The 2.4 kcal mol(-1) greater stabilization of the transition state for cleavage of the minimal substrate HpPNP compared to the nucleoside substrate UpPNP by the efficient dinuclear metal ion catalyst Zn2(L2O) provides evidence that access to the cationic core of Zn2(L2O) is sterically blocked for the bulkier nucleoside substrates, a flaw that will need to be dealt with in later generations of metal ion catalysts of RNA cleavage.     

The synthesis and structure of 10,11-bistrifluoromethyl-i,o-bicyclo[7.2.2]trideca-10,12-diene. A highly strained inside-outside bicycloalkane derivative.

10,11-Bistrifluoromethyl-i,o-bicyclo[7.2.2]trideca-10,12-diene has been prepared by the Diels-Alder addition of hexafluoro-2-butyne to cis, trans-cycloundeca-1,3-diene. Purification was accomplished via formation of an iron tricarbonyl complex whose structure was established via X-ray crystallography.     

A pulse polarographic investigation of parathion and some other nitro-containing pesticides

The polarographic behaviour of parathion, its major metabolites (paraoxon and p-nitrophenol), and of methylparathion, EPN and pentachloronitrobenzene has been studied over a wide pH range. Differential pulse polarography is used to differentiate between parathion, p-nitrophenol and pentachloronitrobenzene. An indirect determination of parathion in the presence of paraoxon can be based on their respective rates of hydrolysis in 0.5 M sodium hydroxide solution. The electrochemical behaviour of these compounds has also been investigated in solutions containing tetraalkylammonium salts as the supporting electrolyte.     

Preparation and characterization of rhenium(I) compounds with amino ester derivatized diimine ligands. Investigations of luminescence. Crystal structures of Re(CO)3Cl(pyca-β-Ala-OEt) and Re(CO)3Cl(pyca-l-Asp(OMe)-OMe)

The title compounds were prepared in good yield by heating ester protected amino acids (H-l-Ala-OEt, H-β-Ala-OEt, H-L-Val-OMe, H-GABA-OMe, H-L-Asp(OMe)-OMe, H-L-Met-OMe) with Re(CO)₅Cl in the presence of pyridine-2-carboxaldehyde. The resulting novel complexes contain a bound, conjugated diimine ligand with a pendant ester group. All compounds were characterized by ¹H and ¹³C NMR, IR and UV-Vis spectroscopy. Compounds prepared from chiral amino esters give diastereomers because of the presence of a stereogenic metal center. Syntheses using Re(CO)₅Br as starting material were discontinued because of metathesis involving the chloride in the amino ester · HCl salts and the metal bromide. Photophysical studies on Re(CO)₃Cl(pyca-β-Ala-OEt), 2, show that it is luminescent in organic solvents in air at room temperature. The crystal structures of 2 and Re(CO)₃Cl(pyca-l-Asp(OMe)-OMe), 5, were determined.     

The effect of tin(II) chloride on the liquid-liquid extraction of tetrachloroplatinate(II) ions by triphenylphosphine in dichloromethane

The effect of tin(II) chloride on the extraction of tetrachloroplatinate(II) in 1.0–1.5 M HCl into dichloromethane with triphenylphosphine (TPP) is described. Tin(II) chloride dramatically increases the rate and efficiency of platinum extraction. The percentage of platinum extracted depends in a complicated way on the time allowed for extraction, the Pt:Sn(II) ratio, the Pt:TPP ratio, and to a lesser extent to the hydrochloric acid concentration. Tin is initially extracted into the organic phase, probably as [Pt(SnCl₃)Cl(PPh₃)₂], but is subsequently back-extracted into the aqueous phase, as a result of the relatively slow disproportionation reaction: [Pt(SnCl₃)Cl(PPh₃)₂]_org + cl^? ? [Pt(PPh₃)₂Cl₂]_org + SnCl^?₃.     

Structure-activity studies on the cleavage of an RNA analogue by a potent dinuclear metal ion catalyst: effect of changing the metal ion

Dinuclear Cd(II), Cu(II), and Zn(II) complexes of L2OH (L2OH = 1,3-bis(1,4,7-triazacyclonon-1-yl)-2-hydroxypropane) are compared as catalysts for cleavage of the RNA analogue HpPNP (HpPNP = 2-hydroxypropyl 4-nitrophenyl phosphate) at 25 degrees C, I = 0.10 M (NaNO(3)). Zn(II) and Cu(II) readily form dinuclear complexes at millimolar concentrations and a 2:1 ratio of metal ion to L2OH at neutral pH. The dinuclear Zn(2)(L2O) and Cu(2)(L2O) complexes have a bridging alkoxide group that brings together the two cations in close proximity to facilitate cooperative catalysis. Under similar conditions, the dinuclear complex of Cd(II) is a minor species in solution; only at high pH values (pH 10.4) does the Cd(2)(L2O) complex become the predominant species in solution. Analysis of the second-order rate constants for cleavage of HpPNP by Zn(2)(L2O) is straightforward because a linear dependence of pseudo-first-order rate constant on dinuclear complex is observed over a wide pH range. In contrast, plots of pseudo-first-order rate constants for cleavage of HpPNP by solutions containing a 2:1 ratio of Cd(II) to L2OH as a function of increasing L2OH are curved, and second-order rate constants are obtained by fitting the kinetic data to an equation for the formation of the dinuclear Cd(II) complex as a function of pH and [L2OH]. Second-order rate constants for cleavage of HpPNP by these dinuclear complexes at pH 9.3 and 25 degrees C vary by 3 orders of magnitude in the order Cd(2)(L2O) (2.8 M(-)(1) s(-)(1)) > Zn(2)(L2O) (0.68 M(-)(1) s(-)(1)) > Cu(2)(L2O) (0.0041 M(-1) s(-1)). The relative reactivity of these complexes is discussed in terms of the different geometric preferences and Lewis acidity of the dinuclear Zn(II), Cu(II), and Cd(II) complexes, giving insight into the importance of these catalyst properties in the cleavage of phosphate diesters resembling RNA.