Total synthesis of ingenol

Total synthesis of ingenol, a diterpene isolated from the genus Euphorbia, was accomplished on the basis of the novel key reactions. The highly strained ingenane skeleton was constructed through an intramolecular cyclization reaction of an acetylene dicobalt complex followed by a rearrangement reaction of an epoxy alcohol. The C(3),C(4),C(5)-triol moiety was introduced by a stereoselective double dihydroxylation reaction of a diene having C(2)-C(3) and C(4)-C(5) double bonds.     

Fluorinated NAD as an affinity surfactant

Nicatinamide adenine dinucleotide (NAD) with an attached perfluoropolyether tail acts as an affinity surfactant in the extraction of the enzyme horse liver alcohol dehydrogenase (HLADH) from an aqueous medium into a fluorous solvent.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: 2.Benzoxazole complexes

Enthalpies of the overall decomposition reactions

and of the intermediate reactions involving stepwise loss of ligand, L, where M is Mn, Co, Ni, Cu, or Cd, X is Cl or Br, and L is benzoxazole, 2-methylbenzoxazole, or 2,5-dimethylbenzoxazole have been measured by use of a differential scanning calorimeter. Specific heats of CoCl₂(2-methylbenzoxazole)₂, and CoBr₂(2-methylbenzoxazole)₂ are reported together with enthalpies of sublimation of CoCl₂(2-methylbenzoxazole)₂, CoBr₂(2-methyl-benzoxazole)₂, CoCl₂(2,5-dimethylbenzoxazole)₂ and CoBr₂(2,5-dimethylbenzoxazole)₂. Enthalpies of decomposition of benzoxazole complexes are found to be greater than those of the corresponding pyridine complexes, but less than those of the analogous benzothiazole complexes. However, the mean bond dissociation energies of the cobalt—nitrogen and cobalt—oxygen bonds in these complexes are all in the region 33±2 kcal mol^?.     

Synthesis of cationic water-soluble light-harvesting dendrimers

Four generations of phenylenefluorene (1F)- and phenylenebis(fluorene) (2F)-terminated polyamidoamine (PAMAM) dendrimers were synthesized by coupling activated esters with commercially available PAMAM precursors. Treatment of Boc-terminated pendant groups on the optically active units with 3 M HCl in dioxane yields cationic water-soluble dendrimers. Fluorescence resonance energy transfer (FRET) experiments with the cationic dendrimers as the donor and double stranded DNA containing a fluorescein label as the acceptor reveal cooperative optical behavior.     

Supramolecular Cationic Tetraruthenated Porphyrin Induces Single-Strand Breaks and 8-Oxo-7,8-dihydro-2'-deoxyguanosine Formation in DNA in the Presence of Light

Abstract— The aim of this investigation is the evaluation of DNA interaction of with tetraruthenated porphyrin (TRP) and of DNA damage in the presence of light. Direct-fluorescence and electronic absorption measurements after incubation of DNA with TRP indicate strong binding between pBR322 DNA or calf thymus DNA with the modified porphyrin. Exposure of pBR322 DNA to TRP (up to 3 μ M ) and light leads to single-strand break formation as determined by the conversion of the supercoiled form (form I) of the plasmid into the nicked circular form (form II). Oxidative DNA base damage was evaluated by the detection of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) after irradiation of calf thymus DNA in the presence of the TRP. The data demonstrated a dose and time dependence with each type of DNA damage. These data indicate (1) a specificity of the binding mode and (2) type I and II photoinduced mechanisms leading to strand scission activity and 8-oxodGuo formation. Accordingly, singlet molecular oxygen formation, after TRP excitation, was confirmed by near-infrared emission. From these investigations a potential application of TRP in photodynamic therapy is proposed.     

High-pressure syntheses of TaS3, NbS3, TaSe3, and NbSe3 with NbSe3-type crystal structure

Transition metal trichalcogenides TaSe₃, TaS₃, NbSe₃ and NbS₃ were prepared under the reaction conditions of 2 GPa, 700°C, 30 min. NbSe₃ is exactly the same as that obtained in the usual sealed-tube method. The other products are modifications of each usual phase. They have crystal structures very similar to that of NbSe₃. The lattice parameters are a = 10.02Å, b = 3.48 Å, c = 15.56 Å, β = 109.6° for TaSe₃, a = 9.52 Å, b = 3.35 Å, c = 14.92 Å, β = 110.0° for TaS₃, and a = 9.68 Å, b = 3.37 Å, c = 14.83 Å, β = 109.9° for NbS₃. In spite of the similarity in their crystal structures, these high-pressure phases show a variety of electrical transport properties. TaSe₃ is a superconductor having T_c at 1.9 K. TaS₃ is a semiconductor with two transitions at 200 and 250 K. NbS₃ is a semiconductor with E_a = 180 MeV.     

The thermal decomposition of transition-metal complexes containing heterocyclic ligands: 3. Substituted pyridine complexes of cobalt

Enthalpies of the overall decomposition reactions CoX₂L₂(c) → CoX₂(c)+2L(g) and of the intermediate stepwise loss of ligand, L, where X is Cl or Br, and L is 3-chloropyridine, 3-bromopyridine, 2-chloropyridine, 2-bromopyridine, or 2-methoxypyridine have been measured by use of a differential scanning calorimeter. Enthalpies of sublimation of CoCl₂(3-chloropyridine)₂, CoBr₂(3-chloropyridine)₂, CoCl₂(3-bromopyridine)₂, CoCl₂(2-chloropyridine)₂, CoCl₂(2-bromopyridine)₂, CoBr₂(2-bromopyridine)₂, CoCl₂(2-methylpyridine)₂ and CoBr₂(2-methylpyridine)₂ have been determined. Values of the cobalt-nitrogen bond dissociation energies have been calculated. Specific heats of a number of the complexes are reported.     

Symmetrical dinuclear complexes with high DNA affinity based on [Ru(dpq)2(phen)]2+

Symmetrical homometallic dinuclear complexes of the type [(Ru(dpq)2)2(phen-SOS-phen)]4+, with a flexible 2-mercaptoethyl ether linker joining the two [Ru(dpq)2(phen)]2+-based sub-units, have DNA dissociation constants (Kd) in the nM range.