• Buchwald-Hartwig versus Microwave-Assisted Amination of Chloroquinolines: En Route to the Pyoverdin Chromophore

      Seubert, Philipp; Freund, Marcel; Rudolf, Richard; Lin, Yulin; Altevogt, Luca; Bilitewski, Ursula; Baro, Angelika; Laschat, Sabine; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany. (Thieme Verlag, 2020-07-22)
      The reaction of 2-chloro-3-nitroquinoline and a series of amines and aminoalkanoates under basic microwave-mediated conditions and Buchwald-Hartwig amination conditions is reported. The microwave irradiation favored the reaction with amines, resulting in yields up to 80%, while amino acid functionalization gave yields comparable to those of BuchwaldHartwig amination. (2R)-4-[(6,7-dimethoxy-3-nitroquinolinyl)amino]-2-hydroxybutanoate could be successfully cyclized to the pyoverdin chromophore, a subunit of siderophores.
    • Triazole-based cross-linkers in radical polymerization processes: tuning mechanical properties of poly(acrylamide) and poly( -dimethylacrylamide) hydrogels

      Götz, Tobias; Schädel, Nicole; Petri, Nadja; Kirchhof, Manuel; Bilitewski, Ursula; Tovar, Günter E. M.; Laschat, Sabine; Southan, Alexander; HZI,Helmholtz-Zentrum für Infektionsforschung GmbH, Inhoffenstr. 7,38124 Braunschweig, Germany.
      Triazole-based cross-linkers with different spacer lengths and different functional end groups (acrylamides, methacrylamides, maleimides and vinylsulfonamides) were synthesized, investigated for cytotoxic and antibacterial activity, and incorporated into poly(acrylamide) (PAAm) and poly(N,N-dimethylacrylamide) (PDMAAm) hydrogels by free-radical polymerization. Hydrogels prepared with different cross-linkers and cross-linker contents between 0.2% and 1.0% were compared by gel yields, equilibrium degrees of swelling (S) and storage moduli (G0). Generally with increasing cross-linker content, G0 values of the hydrogels increased, while S values decreased. The different polymerizable cross-linker end groups resulted in a decrease of G0 in the following order for cross-linkers with C4 spacers: acrylamide > maleimide > methacrylamide > vinylsulfonamide. Longer cross-linker alkyl spacer lengths caused an increase in G0 and a decrease in S. Independent of the cross-linker used, a universal correlation between G0 and equilibrium polymer volume fraction f was found. For PAAm hydrogels, G0 ranged between 4 kPa and 23 kPa and f between 0.07 and 0.14. For PDMAAm hydrogels, G0 ranged between 0.1 kPa and 4.9 kPa and f between 0.02 and 0.06. The collected data were used to establish an empirical model to predict G0 depending on f. G0 of PAAm and PDMAAm hydrogels is given by G0 ¼ 4034 kPa f2.66 and G0 ¼ 4297 kPa f2.46, respectively.