Γ-Lakton-cis-anellierung an Δ2- und Δ3- Cholesten

γ-Lactone-cis-annulation to Δ²- and Δ³- Cholestene. From Δ²- and Δ³- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The ¹³C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported.     

Ternary Fission

In this review paper, ternary fission is defined as the break-up of heavy nuclei into three fragments of approximately equal mass. This relatively new type of nuclear decay has been investigated intensively during the last decade. Muga has studied ternary fission induced by thermal neutrons in uranium. The results of his experiments are discussed in detail. Ternary fission can definitely be observed and studied in the interaction of heavy target elements with 39 MeV alpha particles, 20 GeV protons, and 300—400MeV argon ions. The ratio of binary-to-binary fission for uranium is approximately 10^?4: 100 in the interaction of 39 MeV alpha particles, approximately 0.1:100 for 20 GeV protons, and 3:100 for 400MeV argon ions. A theoretical model for the interpretation of ternary fission, the “cascade model”, is described. The paper concludes with a discussion of the possible connection of ternary fission with the production and decay of still undiscovered super-heavy elements (Z = 114).     

Invertebrate organisms as biological indicators of heavy metal pollution

Some species of invertebrate animals are known to be efficient accumulators of trace elements. Generally, metal accumulation by such organisms is based on efficient detoxification mechanisms, such as intracellular compartmentalization, or metal inactivation by binding to metallothioneins. Metal accumulators have often been used as accumulation indicators of environmental metal pollution. This means that, ideally, metal concentrations in the animal’s body reflect quantitatively or semiquantitatively environmental pollution levels. In reality, however, many factors, such as the animal’s weight and age, can disturb such quantitative relationships. These factors have, therefore, to be considered carefully before an invertebrate is utilized as accumulation indicator for metal pollution. Apart from accumulation, many invertebrates exposed to elevated metal concentrations respond to this stress by metal-induced synthesis of metallothioneins. Additionally, metallothionein in metal-loaded organisms can be present in different isoforms that are specifically synthesized in response to different metals. These facts make metallothionein a potential biomarker for metal stress in invertebrates. One possibility may be to assess parameters of metallothionein synthesis at the molecular or biochemical level. Moreover, metallothionein isoform patterns could provide information on different isoforms synthesized in response to different metals or chemicals. In any case, however, care must be taken to consider intrinsic physiological parameters, such as nutritional or developmental factors, which could also interfere with metallothionein synthesis.     

1-Methoxycarbonyl-substituiertes 2,3-Dihydropyridin-4(1H)-on (= Methyl-1,2,3,4-tetrahydro-4-oxopyridin-1-carboxylat) als Chromophor für die photochemische [2 + 2]-Cycloaddition

1-Methoxycarbonyl-Substituted 2,3-Dihydropyridin-4(1H)-one(= Methyl 1,2,3,4-Tetrahydro-4-oxopyridine-1-carboxylate) as Chromophore for Photochemical [2 + 2]-Cycloadditions With olefins having an electron-acceptor as well as with olefins having an electron-donor substituent, 1-methoxycarbonyl-substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis-junction. Only the ‘endo’/‘exo’ selectivity at the C-atom bearing the olefin substituent cannot be controlled. The photodimerization of 12 is the only side reaction. Using a slight excess of the olefin, the photodimerization can be suppressed. The protecting group at the N-atom of the dihydropyridinone can be varied in order to introduce an internal sensitizer, as shown with 1-acyl-substituted compound 29 , which underwent the cycloaddition process even with sunlight.     

Photolysis and gas phase pyrolysis of 1,2,3-benzoselenadiazole - matrix-isolation of benzoselenirene

Based on comparative studies on 1,2,3-benzothiadiazole benzoselenirene is identified as an intermediate in the low temperature photolysis and gas phase pyrolysis of 1,2,3-benzoselenadiazole by IR spectroscopy.