- Cobalt complexation with unsymmetrical tripodal ligands
-
The reaction of the aliphatic unsymmetrical tripod [N(CH2CH 2NH2)2(CH2CH2OH)], H 5-1, with cobalt(II) chloride in THF yields after aerial oxidation the dinuclear complex [(H4-1)CoIII(μ-OH)Co III(H4-1)](CoIICl4)Cl, [5](CoCl 4)Cl. The trianion 53- contains two cobalt atoms triply bridged by two alkoxo groups of the singly deprotonated ligand (H 4-1)- and a hydroxo group. The new ligand [N(CH 2CH2CH2NH2)(CH2CH 2OH)2], H4-3, providing an N2O 2 donor set reacts with cobalt(II) chloride to give after aerial oxidation the hexanuclear complex [CoIII4(H 2-3)4CoII2(HOMe)2Cl 2(μ-OH)4], [6]Cl2, containing an unprecedented mixed-valent CoIII4CoII 2 core.
- Jocher, Christoph,Pape, Tania,Hahn, F. Ekkehardt
-
p. 667 - 672
(2007/10/03)
-
- Synthesis and properties of oligo-2′-deoxyribonucleotides containing internucleotidic phosphoramidate linkages modified with pendant groups ending with either two amino or two hydroxyl functions
-
Single and multiple incorporations of stereochemically pure modified dinucleoside-phosphoramidates involving substituent groups ending with bis-hydroxyethyl and bis-aminoethyl groups have been performed into pyrimidic triple helix-forming oligo-2′-deoxyribonucleotides designed to bind parallel to the purine strand of the DNA target. The ability of these modified oligo-2′-deoxyribonucleotides to form triple helices has been studied by UV-melting curve analyses, and circular dichroism. Only the oligonucleotides involving modified phosphate groups with the Rp configuration formed more stable triple helices than did the parent phosphodiester sequences. Incorporating the modifications into the third oligonucleotide strands has little effect on the structure of the triplexes. At pH 7, the incorporation of two, three or four modified phosphate groups into the third strands stabilizes the triplexes, as compared to the unmodified oligonucleotide. Stronger stabilization was observed with compounds containing linkers ending with amino functions. Stability increases with the number of modifications without being fully additive. This might be due to the different environments of the phosphate groups inside the sequence.
- Asseline, Ulysse,Chassignol, Marcel,Draus, Jolanta,Durand, Maurice,Maurizot, Jean-Claude
-
p. 3499 - 3511
(2007/10/03)
-
- Synthesis and DNA-Sequence Selectivity of a Series of Mono- and Difunctional 9-Aminoacridine Nitrogen Mustards
-
The aim of this work was to identify nitrogen mustards that would react selectively with DNA, particularly in G-rich regions.A series of mono- and difunctional nitrogen mustards was synthesized in which the (2-chloroethyl)amino functions were connected to the N9 of 9-aminoacridine by way of a spacer chain consisting of two to six methylene units.The length of the spacer chain connecting the alkylating and putative DNA-intercalating groups was found to affect the preference for the alkylation of different guanine-N7 positions in a DNA sequence.All of the compounds reacted preferentially at G's that are followed by G as do most other types of nitrogen mustards, but the degree of selectivity was greater.The compounds reacted at much lower concentrations than were required for comparable reaction by mechlorethamine (HN2), consistent with initial noncovalent binding to DNA prior to guanine-N7 alkylation.The degree of DNA-sequance selectivity increased as the spacer-chain length decrease below four methylene units.Most strikingly, long spacer compounds reacted strongly at 5'-GT-3' sequences, whereas this reaction was almost completely suppressed when the spacer length was reduced to two or three methylenes.Mono- and difunctional compounds of a given spacer length showed no consistent difference in DNA-sequence preference.
- Kohn, Kurt W.,Orr, Ann,O'Connor, Patrick M.,Guziec, Lynn James,Guziec, Frank S.
-
-
- Hydroformylation of olefins using azoxy-dentated ligands
-
At a temperature in the range 100° C to 225° C the destructive dissociation of cobalt carbonyl compounds to cobalt metal and residue is inhibited by the action of one or more azoxy-dentated chelation ligands.
- -
-
-
