Computational Studies on the Diastereospecific Lithium Variant of Oppenauer Oxidation of a Tofisopam Intermediate.

During the synthesis of tofisopam drug substance, an interesting diastereospecific lithium variant of Oppenauer oxidation was observed and investigated by density functional theory (DFT) calculations. The computations revealed energetic differences caused by steric differences between the diastereomers that might provide an explanation for the experimentally formed products. In addition, the trend in the measured NMR shifts was also in line with the computed values, which allowed the assignment of the absolute configuration of the diastereomers.

Distribution of Pb, Sr, and U isotopic signature and multielement composition of sediment in Lake Balaton (Hungary) at a sediment trap deep dredged 40 years ago near Balatongyörök-search for routes of recent pollution.

We studied the Pb, Sr, and U isotopic composition and the concentration of toxic metal elements in sediment core samples collected in Lake Balaton at a sediment trap that was deep dredged in 1979, to analyze their changes in the last 40 years. Pb isotopic composition profiles of cores taken from the sediment trap showed different 206Pb/207Pb ratios ranging from 1.206 ± 0.002 at the bottom of the core (phase 1) compared to 1.185 ± 0.002 at the top of the core (phase 2). Phase 2 is the fraction reflecting isotopic signatures of the latest 40 years. At 80-100-cm depth, a transition zone was observed. Pb concentration together with Zn, Sb, Cu, Cd, and Fe showed elevated, 2-4 times higher values in the top phase of the sediment. The calculated Pb isotopic composition of pollutant Pb fraction was 1.177 ± 0.005 in the case of the 206Pb/207Pb and 2.456 ± 0.004 for 208Pb/207Pb, which shows good agreement with literature data for lead ores in Poland and Germany, but it is distinct from literature data for leaded fuel concerning Middle and Eastern Europe. The marked difference in the Pb signatures of phases enabled the construction of a sediment deposition rate map. U and Mo showed a characteristic concentration peak positioned exactly at the depth of the Pb signature transition. The isotopic signature of U based on 234U and 235U also showed a similar pattern. We suggest that the deposition of U and Mo can be related to cyanobacterial blooms in Lake Balaton in the late 1970s and early1980s.