Metal-Free Twofold Electrochemical C−H Amination of Activated Arenes: Application to Medicinally Relevant Precursor Synthesis

The efficient production of many medicinally or synthetically important starting materials suffers from wasteful or toxic precursors for the synthesis. In particular, the aromatic non-protected primary amine function represents a versatile synthetic precursor, but its synthesis typically requires toxic oxidizing agents and transition metal catalysts. The twofold electrochemical amination of activated benzene derivatives via Zincke intermediates provides an alternative sustainable strategy for the formation of new C−N bonds of high synthetic value. As a proof of concept, we use our approach to generate a benzoxazinone scaffold that gained attention as a starting structure against castrate-resistant prostate cancer. Further improvement of the structure led to significantly increased cancer cell line toxicity. Thus, exploiting environmentally benign electrooxidation, we present a new versatile and powerful method based on direct C−H activation that is applicable for example the production of medicinally relevant compounds.     

Unexpected electron transfer in cryptochrome identified by time-resolved EPR spectroscopy

Subtle differences in the local sequence and conformation of amino acids can result in diversity and specificity in electron transfer (ET) in proteins, despite structural conservation of the redox partners. For individual ET steps, distance is not necessarily the decisive parameter; orientation and solvent accessibility of the ET partners, and thus the stabilization of the charge-separated states, contribute substantially.     

Substituted 1,2-Thiazetidine 1,1-Dioxides. Synthesis of (<Emphasis Type="Italic">RS</Emphasis>)- and (<Emphasis Type="Italic">S</Emphasis>)-1,2-Thiazetidine-3-acetic Acid 1,1-Dioxide and its Reactions with Amino Acids and Dipeptides

Summary. (RS)-2-tert-Butyldimethylsilyl-1,2-thiazetidine-3-acetic acid 1,1-dioxide prepared from (RS)-S-benzyl--homocysteine was condensed via DCC/NHS with various L-amino acid esters or dipeptide esters yielding N-silylated -sultam peptides. A -sultam active ester was isolated as an intermediate. Desilylation with TBAF in THF yielded stable N-unsubstituted products, and deprotection of the benzyl esters was achieved by catalytic hydrogenation. (S)-S-Benzyl--homocysteine was obtained by fractional crystallization of the brucine salt of the racemate and transformed into benzyl (S)-1,2-thiazetidine-3-acetate, which was on the other hand synthesized by an enantiospecific route from -benzyl Boc-L-aspartate. Some -sultam peptides were prepared from the (S)-enantiomer, and finally some -sultam peptides containing D-Ala units were obtained.     

Detection of bis(sulfosuccinimidyl) suberate binding in electrophoresis: determination of membrane sidedness of proteins

The applicability of the membrane-impermeant protein cross-linker bis(sulfosuccinimidyl) suberate (BS(3)) to the determination of membrane sidedness of proteins was tested in 3T3-L1 cells and in erythrocytes. Binding of BS(3) to proteins was apparent in electrophoresis. In three proteins of 3T3-L1 cells, protein kinase-Cepsilon, protein kinase-Czeta, and glyceraldehyde-3-phosphate dehydrogenase, BS(3) action was detectable in SDS-PAGE with immunoblotting. This enabled confirmation of the well-known intracellular localization of these proteins. In cathepsin E of erythrocytes, a mobility increase in nondenaturing PAGE was the most prominent effect of BS(3) treatment. A mechanism for the increase in mobility due to BS(3) binding is suggested. Cathepsin E was found to be located at the intracellular side of the membrane, in accordance with existing evidence.     

Transition properties from multiple scattering X-Alpha Calculations: A study of NO2

The usefulness of the MS -X_α method for calculating molecular transition properties is investigated in a study of NO₂. Two-dimensional potential surfaces are obtained in C_2v symmetry for the X?²A₁/òB₂ system. Potential curves that approximately follow the asymmetric stretch coordinate are also presented: On investigation, no symmetry-broken solutions were found. At all nuclear geometries investigated, the muffin-tin sphere radii were chosen by an energy-minimization technique. The inclusion of corrections to the muffin-tin form of the X_α total energy is shown to be essential, if the computed surfaces are to be qualitatively correct. The transition dipole moment connecting the two states is evaluated as a function of nuclear coordinates, using the transition-state approximation. Finally, the radiative decay of a single vibronic level in NO₂ is modeled and the relevance to experiment is discussed.     

Oleogels—Their Applicability and Methods of Characterization

Oleogels or, more precisely, non-triglyceride structured lipid phases have been researched excessively in the last decade. Yet, no comprehensive knowledge base has emerged, allowing technology elevation from the laboratory bench into the industrial food application. That is partly due to insufficient characterization of the structuring systems studied. Examining a single composition decided upon by arbitrary methods does not stimulate progress in the research and technology area. A framework that gives much better guidance to product applications can easily be derived. For example, the incremental structure contribution concept is advocated as a parameter to compare the potency of structuring systems. These can straightforwardly be determined by combining solubility data and structural measurements in the recommended manner. The current method to determine the oil-binding capacity suffers from reproducibility and relevance. A newly developed method is suggested to overcome these shortcomings. The recommended new characterization of oleogels should contribute to a more comprehensive knowledge base necessary for product innovations.