Total synthesis and stereochemistry of the antitumor antibiotic PD 113,271

[Structure: see text] A total synthesis of PD 113,271, an antitumor fostriecin analogue isolated from Streptomyces pulveraceus, was achieved by the chiral pool approach starting with D-galactose and L-tartaric acid. The synthesis of PD 113,271 led to unambiguous assignment of the relative and absolute stereochemistry of its stereocenters.     

A singular Cauchy problem for the Euler–Poisson–Darboux equation

We consider a singular Cauchy problem for the Euler–Poisson–Darboux equation of Fuchsian type in the time variable with ramified Cauchy data. In this paper we establish an expansion of the solutions in a series of hypergeometric functions and then investigate the nature of the singularities of the solutions.     

Subexponential Densities of Infinitely Divisible Distributions on the Half-Line

Lithuanian Mathematical Journal - Abstract. We show that, under the long-tailedness of the densities of normalized Lévy measures, the densities of infinitely divisible distributions on the...     

Radical ring-opening polymerization behavior of vinylcyclopropane derivatives bearing an ester group

Ethyl 2-vinylcyclopropanecarboxylate derivatives (VCP) that underwent radical ring-opening polymerization were prepared from the corresponding diene and diazoacetate in the presence of copper-Schiff base complex as a catalyst. The polymerization behavior of the obtained monomers was investigated, and the reaction of VCP with thiophenol was also carried out as a model reaction of their polymerization.     

Diels-Alder reactions of nitro-2(1H)-pyridones with 2,3-dimethyl-1,3-butadiene

Diels-Alder (DA) reactions of 3- or 5-nitro-2(1H)-pyridones and nitro-2(1H)-pyridones containing a methoxycarbonyl group with 2,3-dimethyl-1,3-butadiene were examined. The DA reactions of 3-nitro-2(1H)-pyridones in this paper represent, to the best of our knowledge, the first report of DA reactions of 3-substituted 2(1H)-pyridones and consequent production of isoquinolones. Performing the same reactions with 5-nitro-2(1H)-pyridones yielded quinolones. DA reactions of 2(1H)-pyridones with nitro and methoxycarbonyl groups produced isoquinolones, quinolones and phenanthridones (the double DA adducts), aromatized or hydrogenated. The substituent effect was evaluated by calculating the activation energy, using the ab initio MO method.     

Diffusion of Si-acceptor in δ-doped GaAs grown on GaAs(111)A by molecular beam epitaxy

Diffusion of Si-acceptors (Si occupying As sites) in δ-doped GaAs grown on GaAs(111)A has been investigated by secondary ion mass spectrometry (SIMS). We have measured the diffusion parameters in GaAs(111)A and found that they differ from those in GaAs(001). The diffusion coefficient in GaAs(111)A is smaller than that in GaAs(001) and the activation energy in GaAs(111)A is larger than that in GaAs(001). Furthermore, the diffusion mechanism of Si in GaAs(111)A has been investigated by photoluminescence; we have found that in p-type layers Si-donors (Si occupying Ga sites) diffuse easily to As sites. The activation energy of Si-acceptor diffusion is 2.74±0.11 eV. These results indicate that Si-acceptors are more stable than Si-donors.     

The reducing rate of radiocesium 137Cs in the North Pacific surface water after the TEPCO fukushima Dai-ichi nuclear power plant accident

Journal of Radioanalytical and Nuclear Chemistry - We started monitoring the radiocesium released from Fukushima in the North Pacific surface water from May 2011 after the accident soon to June...