Untersuchungen zur Synthese von Dihydropyridin-Systemen durch photochemische Cycloaddition Abschlussbericht zum Forschungsvorhaben

SIGLETIB: D.Dt.F./AC 1000 (17,43) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Untersuchungen zur Synthese von Alkaloiden durch photochemische Cycloaddition von Enamincarbaldehyden mit Olefinen

SIGLETIB: D.Dt.F./AC 1000 (22,33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Reverse lectin histochemistry: Design and application of glycoligands for detection of cell and tissue lectins

Plant and invertebrate lectins are valuable cyto- and histological tools for the localization of defined carbohydrate determinants. The welldocumented ubiquitous occurrence of sugar receptors encourages functional considerations. Undoubtedly, analysis of the presence of vertebrate lectins in tissues and cells is required to answer the pertinent and tempting question on the physiological relevance of protein (1ectin)-carbohydrate recognition in situ. Carrierimmobilized glycoligands, derived from custom-made chemical synthesis, enable the visualization of respective binding sites. Histochemically inert proteins or synthetic polymers with appropriate functional groups are suitable carrier molecules for essential incorporation of ligand and label. The resulting neoglycoconjugates can track down tissue receptors that are neither impaired by fixation procedures nor blocked by endogenous highaffinity ligands. Lectins, especially the receptors of the tissue under investigation (endogenous lectins), and appropriately tailored immobilized glycoligands or lectin-specific antibodies (when available) are complementary tools to test the attractive hypothesis that diverse, functionally relevant glycobiological processes within or between cells are operative. Concomitant evaluation of both sides of lectin histochemistry, namelylectins as tools and lectins as functionally important molecules in situ, will indubitably render desired progress amenable in our often still fragmentary understanding of the importance of tissue lectin and glycoconjugate expression and its regulation

A facile synthesis of 2-aryloxypyrimidine derivatives via a tandem reductive amination/intermolecular SNAr sequence*

A novel tandem reductive amination/intermolecular nucleophilic aromatic substitution (SNAr) sequence has been established for the synthesis of amine containing pyrimidine in formation of one carbon-oxygen and one carbon-nitrogen bonds in a one-pot fashion. Treatment of aldehyde with arylamine, 2-methanesulfonyl-4,6-dimethoxypyrimidine and sodium borohydride provides good overall yield. The p-toluenesulfonic acid (PTSA) can be used as activator and is generally needed in the reaction. Dioxane is the preferred reaction solvent, but reactions can also be carried out in tetrahydrofuran (THF), MeCN, toluene and dichloromethane. The procedure is carried out effectively in the presence of K2CO3. The reaction proceeds smoothly with aromatic aldehydes and arylamines possessing electron-donating or -withdrawing groups. This method can be applied to the synthesis of the oilseed rape herbicide and is superior to the classical one in several aspects: cutting out several purification steps, minimizing solvent use and chemical waste, and saving time. Its advantages such as operational convenience, high-efficient synthesis, and starting material availability make it a desirable method for preparing amines with molecular diversity and biological activity