Über die Umsetzung des Nα-Tosylglycinäthylester-isonicotinoylhydrazons mit Hydrazin und Hydrazinabkömmlingen

Zusammenfassung N-Tosylglycinäthylester-isonicotinoylhydrazon (1) reagiert vorwiegend unter Hydrazinolyse sowohl der C,N-Doppelbindung wie auch der Esterbindung zum unbeständigen Hydrazidin2, das sich in bekannter Reaktion zu4 und5 umsetzt.Eine durch ausschließliche Hydrazinolyse der Esterbindung von1 zu postulierende Acylhydrazidinzwischenstufe3 ist in Form des N⁴-Amino-1,2,4-triazols6 nachweisbar. Es werden ferner die ähnlich verlaufenden Reaktionen von Methyl-, N,N-Dimethyl- und Benzylhydrazin mit1 beschrieben.Phenylhydrazin, p-Tolylhydrazin, p-Chlor- und p-Brom-phenylhydrazin reagieren mit1 unter Bildung der N¹,N⁵-diarylsubstituierten Formazane11 b–d und der am N⁴-arylaminosubstituierten 1,2,4-Triazole12 a–d. Im Gegensatz hierzu wird mit p-Nitrophenylhydrazin das Tosylglycinäthylester-p-nitrophenylhydrazon (13 e) erhalten.

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The reaction of N-tosylglycine ethyl ester isonicotinoylhydrazone with hydrazine and hydrazine derivatives

N-Tosylglycine ethyl ester isonicotinoylhydrazone (1) undergoes hydrazinolysis both of the C,N double bond and of the ester bond to yield as major product the unstable hydrazidine2, which reacts in a known manner to yield4 and5.An acyl hydrazidine3 postulated as an intermediate formed by hydrazinolysis of the ester bond alone can be isolated in the form of N⁴-Amino-1.2.4-triazole (6). The analogous reactions of methyl-, N.N-dimethyl- and benzylhydrazine with1 are also described.Phenylhydrazine, p-tolylhydrazine, p-chloro- and p-bromophenylhydrazine react with1 to form the N¹,N⁵-diaryl substituted formazans11 b–d and the N⁴-arylamino-1.2.4-triazoles12 a–d. With p-nitrophenylhydrazine, however, the tosylglycine ethyl ester-p-nitrophenylhydrazone is obtained.

     

Uniqueness and wavelength optimization in continuous-wave multispectral diffuse optical tomography

We derive conditions for the unique and simultaneous recovery of chromophore concentrations and scattering coefficients in multispectral continuous-wave diffuse optical tomography. These conditions depend strongly on measurement wavelengths. We introduce and demonstrate a general methodology for choosing those wavelengths, which yields superior separation of scattering from absorption and superior separation of one chromophore from another. Application of these concepts should significantly improve the fidelity of continuous-wave diffuse near-infrared optical tomography in tissues.     

Soluble molecular compounds with the Mg-O-Al structural motif: a model approach for the fixation of organometallics on a MgO surface

We report a facile route to the molecular compounds with the Mg-O-Al structural motif. The reaction of Mg[N(SiMe3)2]2 (1) with a stoichiometric amount of LAlOH(Me) (2) [L = CH{(CMe)(2,6-iPr2C6H3N)}2] in THF/n-hexane at 0 degrees C results in the formation of the heterobimetallic compound (Me3Si)2NMg(THF)2-O-Al(Me)L (3) in high yield. The similar reaction of 1 equiv of Mg[N(SiMe3)2]2 and 2 equiv of LAlOH(Me) results in the formation of trimetallic compound L(Me)Al-O-Mg(THF)2-O-Al(Me)L (4). Structural analyses of 3 and 4 have been carried out, revealing the presence of the Mg-O-Al motif. A tentative assignment of the Mg-O-Al vibrations has been made and was supported by calculations.     

On-line protein digestion and peptide mapping by capillary electrophoresis with post-column labeling for laser-induced fluorescence detection

A nanoliter enzyme microreactor was developed for on-line capillary electrophoresis (CE) peptide mapping of proteins, allowing picomole quantities of proteins to be digested. The enzyme microreactor was formed by immobilizing trypsin onto a monolithic capillary column, which was prepared by in situ polymerization of glycidyl methacrylate and ethylene dimethacrylate in a capillary. Highly efficient digestion of three protein standards was demonstrated. The detection of peptide fragments in CE was enhanced by post-column derivatization and laser-induced fluorescence detection. The microreactor has a volume of about 30 nL and is coupled with a separation capillary via a fluid joint for on-line digestion. The overall analysis, including digestion and separation, lasted only about 16 min. Column efficiencies > 300 000 plates/m were obtained for most peaks in the electropherogram of an on-line peptide mapping experiment of denatured alpha-lactalbumin under optimal conditions.     

A seven-membered aluminum sulfur allenyl heterocycle arising from the conversion of an aluminacyclopropene with CS2

The reaction of an aluminacyclopropene LAl[eta2-C2(SiMe3)2] (1, L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) with CS2 in the temperature range from -78 degrees C to room temperature affords the first seven-membered aluminum sulfur-containing heterocyclic compound [LAl]2(mu-S)[eta2-SC(SiMe3)=C=C(SiMe3)] (2) bearing an allenyl group. The structural characterization of 2 and the analogous compound LAl[OC(O)C2(SiMe3)2] (3) of the proposed intermediate A and the variable-temperature 1H NMR kinetic study of this reaction may give a better understanding on this unusual conversion.