Branching of anionic poly(methyl methacrylate)

A viscometric determination of the degree of branching γ, of poly(methyl methacrylate) obtained by anionic polymerization proved the reaction of the growing center of poly(methyl methacrylate) with the ester group of another polymer molecule, accompanied by the formation of a trifunctional branch point. This reaction occurs if the solution polymerization of methyl methacrylate is initiated: (1) with butyllithium at ?78°C only on attaining 100% conversion and after a long time or at +20°C immediately after the polymerization has set in; (2) with lithium <i>tert</i>-butoxide at +20°C after a long time. The degree of branching of poly(methyl methacrylates) obtained under similar conditions in the presence of tetrahydrofuran reaches higher values than for polymers prepared in toluene. The tacticity of polymers does not affect the experimentally determined γ values.     

Stereochemical studies—76 saturated heterocycles—63 : synthesis of cis- and trans-n-methyl- and n-benzyl-4.5- and 5,6-tetramethylenetetrahydro-1,3-oxazines; an x-ray study of n-benzyl-cis-4,5-tetramethylenetetrahydro-1,-3-oxazinium- picrate

- The corresponding <math><mtext>cis</mtext></math>- and <math><mtext>trans-N</mtext></math>-methyl- and <math><mtext>N</mtext></math>-benzyl-5,6- and 4,5-tetramethylenetetrahydro-l,3-oxazines <math><mtext>(5a,b-8a,b)</mtext></math>were synthesized from <math><mtext>cis</mtext></math>- and <math><mtext>trans-N</mtext></math>-methyl and<math><mtext>N</mtext></math>-benzyl-2- aminomethyl-1-cyclohexanols <math><mtext>1a,b,2a,b</mtext></math>, from <math><mtext>cis</mtext></math>- and <math><mtext>trans-N</mtext></math>-methyl- and <math><mtext>N</mtext></math>benzyl -2-hydroxymethyl-1-cyclohexylamines<math><mtext>(3a,b,4a,b)</mtext></math> by reaction with formaldehyde. The aminoalcohols <math><mtext>1a,2a,3a,b</mtext></math>and <math><mtext>4a,b</mtext></math> were prepared in considerably higher yields than in earlier procedures. NMR spectroscopy showed that the <math><mtext>cis</mtext></math> isomers of the synthesized oxazines were conformationally homogeneous in solution, and their preferred conformation (inside or outside) depended on the steric requirement of the groups attached to the anellation points, whereas a bulky C-2 substituent had no influence on the predominant conformation. The structure of <math><mtext>N</mtext></math>-benzyl-<math><mtext>cis</mtext></math>-4,5-tetramethylenetetrahydro-1,3-oxaziniumpicrate <math><mtext>(7b)</mtext></math>. determined by X-ray diffraction analysis, was in agreement with the predominant N-outside conformation of the corresponding base, established by means of NMR spectroscopy.     

Hydrogenation and double bond isomerization of hexenes over EUROPT-1

Hexenes give large amounts of hexane and isomeric hexenes over EUROPT-1. A constant hydrocarbon coverage can be assumed in the steady-state period of the reaction; the direction of reactions of these surface species depends on the hydrogen excess and also on the structure of starting hydrocarbon.<hr><blockquote><img src="/content/q46608767725v334/xxlarge1043.gif" alt="Gcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1085.gif" alt="ncy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1085.gif" alt="ncy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"> EUROPT-1 <img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1102.gif" alt="yucy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1074.gif" alt="vcy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1073.gif" alt="bcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1100.gif" alt="softcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1096.gif" alt="shcy" 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alt="acy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1087.gif" alt="pcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1074.gif" alt="vcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1085.gif" alt="ncy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1080.gif" alt="icy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" 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BORDER="0"><img src="/content/q46608767725v334/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1080.gif" alt="icy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1080.gif" alt="icy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1079.gif" alt="zcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1073.gif" alt="bcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1074.gif" alt="vcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0">, <img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1078.gif" alt="zhcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1091.gif" alt="ucy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1082.gif" alt="kcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1090.gif" alt="tcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1091.gif" alt="ucy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1099.gif" alt="ycy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1080.gif" alt="icy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1089.gif" alt="scy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1093.gif" alt="khcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1085.gif" alt="ncy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"> <img src="/content/q46608767725v334/xxlarge1091.gif" alt="ucy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1075.gif" alt="gcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1083.gif" alt="lcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1077.gif" alt="iecy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1074.gif" alt="vcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1088.gif" alt="rcy" align="MIDDLE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1086.gif" alt="ocy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1076.gif" alt="dcy" align="BASELINE" BORDER="0"><img src="/content/q46608767725v334/xxlarge1072.gif" alt="acy" align="BASELINE" BORDER="0">.</blockquote><hr><hr><p></p>Based on the diploma work of Mr. M. Räth and Ms. B. Brose.     

Synthesis and 13C-NMR spectroscopic investigations of rhamnobioses

A convenient method has been developed for the synthesis of all mono- and di-O-benzyl ethers of methyl α-L-rhamnopyranoside applying a new stereoselective method for the hydrogenolytic ring-cleavage of benzylidene acetals. Using the prepared dibenzyl ethers as aglycones, the (1→2)-, (1→3)- and (l→4)-linked rhamnosyl-rhamnose derivatives (<strong>13</strong>–<strong>15</strong>) were synthesised. Hydrogenolysis of the latter compounds and subsequent acetylation gave the pentaacetates (<strong>16</strong>–<strong>18</strong>) of methyl dirhamnosides, which on saponification furnished the free methyl dirhamnosides (<strong>19</strong>–<strong>21</strong>). Acetolysis of <strong>16</strong>–<strong>18</strong> gave the corresponding dirhamnose-hexaacetates which were transformed into the three disaccharides by saponification. The structure of each product was investigated by <sup>13</sup>C-NMR spectroscopy, and for the purpose of <sup>13</sup>C-NMR studies the mono-O-methyl ethers of methyl α-L-rhamnopyranoside, the diacetates and di-O-benzyl ethers of the latter compounds, and, also the diacetates of methyl α-L-rhamnopyranoside were synthesised.It has been established that, for <sup>13</sup>C-NMR investigations of oligosaccharides, the benzyl ethers of monosaccharides are more suitable model compounds than the currently used monosaccharide methyl ethers.     

Primary photodamage sites and mitochondrial events after Foscan photosensitization of MCF-7 human breast cancer cells

To determine the initial photodamage sites of Foscan-mediated photodynamic treatment, we evaluated the enzymatic activities in selected organelles immediately after light exposure of MCF-7 cells. The measurements indicated that the enzymes located in the Golgi apparatus (uridine 5'-diphosphate galactosyl transferase) and in the endoplasmic reticulum (ER) (nicotinamide adenine dinucleotide [reduced] [NADH] cytochrome c [cyt c] reductase) are inactivated by the treatment, whereas mitochondrial marker enzymes (cyt c oxidase and dehydrogenases) were unaffected. This indicates that the ER and the Golgi apparatus are the primary intracellular sites damaged by Foscan-mediated PDT in MCF-7 cells. We further investigated whether the specific mitochondria events could be associated with Foscan photoinduced cell death. The dose response profiles of mitochondrial depolarization and cytochrome c release immediately after Foscan-based PDT were very different from that of overall cell death. By 24 h post-PDT the fluence dependency was strikingly similar for both mitochondrial alterations and cell death. Therefore, although mitochondria are not directly affected by the treatment, they can be strongly implicated in Foscan-mediated MCF-7 cell death by late and indirect mechanism.     

Sodium diffusion through amorphous silica surfaces: a molecular dynamics study

We have studied the diffusion inside the silica network of sodium atoms initially located outside the surfaces of an amorphous silica film. We have focused our attention on structural and dynamical quantities, and we have found that the local environment of the sodium atoms is close to the local environment of the sodium atoms inside bulk sodo-silicate glasses obtained by quench. This is in agreement with recent experimental results.     

The Mitsunobu Inversion Reaction of Sterically Hindered 17-Hydroxy Steroids

The <i>Mitsunobu</i> inversion reaction of 3-methoxyestra-1,3,5(10)-trien-17<img src="/content/5WT76CLCW3JYPX29/xxlarge946.gif" alt="beta" align="MIDDLE" border="0">-ol is dramatically influenced by the acidic component. There appears to be a relationship between the dissociation constant of the electron-withdrawing substituent on the aryl acid and the overall effectiveness of the reaction, with more acidic species generally providing a higher yield of inverted product.     

Antibakterielle wirkstoffe. VIII . Die aminomethinylierung in der reihe der aminothiazole

The three-component reaction comprising the interaction of 2-amino-4-antipyrinyl-5-ethylthiazole (1) with s-triazine (2) and pyrrolidine leads to 4-anitpyrinyl-5-ethyl-2-[(4-pyrrolidinyl)methyleneamino]thiazole (5). Structure 5 is supported by <sup>1</sup>H- and <sup>13</sup>C-NMR spectroscopy.     

On triazoles. VII Synthesis of novel tri- and tetracyclic ring systems

The ring-closure of the 5-amino-1-(2-aminophenyl)-3-methylthio-1<i>H</i>-1,2,4-triazole derivatives 3 and 4 with different simple and cyclic C<sub>1</sub> components lead to the formation of 1,2,4-triazolo[1,5-α]-1,3,5-benzotriazepines 5–6 , their 4,5-dihydro- 7 , different 5-spiro-homocyclic- 8–13 , and 5-spiro-heterocyclic- 14-15 analogues. The structure of the compounds obtained was proved with the use of their ir, uv, <sup>1</sup>H-nmr and <sup>13</sup>C-nmr spectra.     

Chemical modification of the surface of a sulfonated membrane by formation of a sulfonamide bond

This paper describes a novel approach for the surface modification of a cation-exchange membrane, bearing sulfonate groups, by a cationic layer. The modification procedure involved the chlorosulfonation of the sulfonate groups of the base membrane with thionyl chloride, followed by a reaction with a diamine to yield a sulfonamide bond and a terminal amine. The latter could be quaternized by reaction with methyl iodide or protonated by soaking in acidic media. The membranes were characterized in detail by attenuated total reflectance Fourier transform infrared and X-ray photoelectron spectroscopies as well as elemental analysis to confirm that the above reactions occurred. The selectivity of these membranes toward the electrochemically assisted transport of protons versus Zn2+ metallic cations was determined during an electrodialysis in a two-compartment electrochemical cell. The data indicate a significant decrease of the transport of the metallic cations following modification of the membrane with the cationic layer. The later allows for the transport of protons from the catholyte to the anolyte compartment with much improved selectivity since the divalent cations are excluded from the membrane due to the electrostatic barrier of the cationic layer.