4-Aminobicyclo[2.2.2]octan-2-ones and -ols via Enamine Intermediates

The synthesis of new bicyclo[2.2.2]octane derivatives is described and their structures were established by NMR experiments. All compounds were tested in in vitro assays for their activities against causative organisms of malaria and African sleeping sickness and compared to those of former synthesized compounds.     

Xanthene dye functionalized norbornenes for the use in ring opening metathesis polymerization

A convenient synthetic route towards polymerizable fluorescein, dicholorofluorescein, and eosin dyes is presented. Polymerizability was provided by linking 2‐norbornene carboxylic acid, 11‐bromo‐undecyl ester to the dye's carboxylate functionality. Although the monomers bearing dichlorofluorescein and eosin were obtained in high yield, the related fluorescein bearing monomer could only be obtained in low yield. In the latter case, concurring etherification and esterification led to a product mixture of the desired carboxy modified monomer and a double substituted by‐product. The dye‐monomers were used successfully for the preparation of statistical copolymers with endo,exo‐2,3‐norbornene dicarboxylic acid dimethylester by ROMP. Absorption and luminescence characteristics and, in particular, the acid/base sensitive behavior of the parent dyes were preserved in the monomers and copolymers. The absorption and emission maxima in THF solution and in the solid state were red shifted in comparison to the aqueous samples of the parent dyes. Dye‐copolymers exhibited good film forming properties. Solid state luminescence studies of the copolymers revealed an increasing sensitivity towards NEt₃ vapor in the order fluorescein < dichlorofluorescein < eosin bearing copolymer. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1336–1348, 2007     

8-Amino-6-Methoxyquinoline—Tetrazole Hybrids: Impact of Linkers on Antiplasmodial Activity

A new series of compounds was prepared from 6-methoxyquinolin-8-amine or its N-(2-aminoethyl) analogue via Ugi-azide reaction. Their linkers between the quinoline and the tert-butyltetrazole moieties differ in chain length, basicity and substitution. Compounds were tested for their antiplasmodial activity against Plasmodium falciparum NF54 as well as their cytotoxicity against L-6-cells. The activity and the cytotoxicity were strongly influenced by the linker and its substitution. The most active compounds showed good activity and promising selectivity.     

Investigation of primary crystallite sizes in nanocrystalline ZnS powders: comparison of microwave assisted with conventional synthesis routes

ZnS powders with primary crystallite sizes of only a few nanometers were prepared by three different synthesis routes at temperatures below 130 degrees C. The reaction of zinc acetate dihydrate with thioacetamide (TAA) in the presence of pyridine and triphenylphosphite (TPP) was carried out using either conventional heating or microwave heating. The obtained powders exhibit sphalerite structure as determined by X-ray diffraction (XRD). The primary crystallites have diameters between 1 and 7 nm obtained by XRD. Small angle X-ray scattering (SAXS) measurements were analyzed by the model-free inverse Fourier-transformation approach, as well as by a hard sphere-model from which particle size and polydispersity were extracted. The particle sizes by SAXS are in good agreement with the primary crystallite sizes obtained by XRD. It has been found that an increasing amount of sulfur and/or using microwave heating increases crystallite sizes. The presence of TPP decreases the particle sizes but no significant influence on the TPP concentration was observed. In the alternative third preparation route, hexamethyldisilathiane (HMDST) was used as precipitation reagent at ambient temperature, which leads to the smallest crystallite sizes of only 1 nm together with low polydispersities. Scanning electron microscopy, dynamic light scattering and UV-vis spectroscopy showed that all three synthesis routes lead to ZnS powders with aggregate sizes between 650 and 1200 nm. Both of the TAA-precipitation routes lead to spherical agglomerates which consist of spherical substructures, whereas the HMDST agglomerates are assembled from elongated objects.     

Highly Defined ABC Triblock Cooligomers and Copolymers Prepared by ROMP Using an N‐Heterocyclic‐Carbene‐Substituted Ruthenium Benzylidene Initiator

The “3^rd generation Grubbs” initiator (H₂IMes)(3‐bromopyridine)₂(Cl)₂RuCHPh ( 1 ) accomplishes the synthesis of ABC triblock copolymers via living ring‐opening metathesis polymerisation (ROMP) of norbornene derivatives. Complete initiation and an outstanding tolerance of functional groups are provided, which is proven by a combined study by means of matrix‐assisted laser desorption/ionisation mass spectrometry, gel permeation chromatography and NMR spectroscopy on an ABC triblock cooligomer.

Gel permeation chromatograms of oligo A , oligo AB , and oligo ABC .