440341-75-3Relevant articles and documents
Sustainable Synthesis of Balsalazide and Sulfasalazine Based on Diazotization with Low Concentrations of Nitrogen Dioxide in Air
Hofmann, Dagmar,Gans, Eva,Krüll, Jasmin,Heinrich, Markus R.
supporting information, p. 4042 - 4045 (2017/03/31)
Low concentrations of nitrogen dioxide, which arises as a side product from a range of industrial processes, can effectively be recycled through the diazotization of anilines. The studies reported herein now demonstrate that the removal of nitrogen dioxide from gas streams is even more effective when hydrophilic anilines are used as starting materials. The diazonium salts, which are obtained in this way in up to quantitative yields, can directly be employed in azo coupling reactions, thus opening up an attractive route to the industrially important group of azo compounds.
Different transition-state structures for the reactions of β-lactams and analogous β-sultams with serine β-lactamases
Tsang, Wing Y.,Ahmed, Naveed,Hinchliffe, Paul S.,Wood, J. Matthew,Harding, Lindsay P.,Laws, Andrew P.,Page, Michael I.
, p. 17556 - 17564 (2007/10/03)
β-Sultams are the sulfonyl analogues of β-lactams, and N-acyl β-sultams are novel inactivators of the class C β-lactamase of Enterobacter cloacae P99. They sulfonylate the active site serine residue to form a sulfonate ester which subsequently undergoes C-O bond fission and formation of a dehydroalanine residue by elimination of the sulfonate anion as shown by electrospray ionization mass spectroscopy. The analogous N-acyl β-lactams are substrates for β-lactamase and undergo enzyme-catalyzed hydrolysis presumably by the normal acylation-deacylation process. The rates of acylation of the enzyme by the β-lactams, measured by the second-order rate constant for hydrolysis, kcat/Km, and those of sulfonylation by the β-sultams, measured by the second-order rate constant for inactivation, ki, both show a similar pH dependence to that exhibited by the β-lactamase-catalyzed hydrolysis of β-lactam antibiotics. Electron-withdrawing groups in the aryl residue of the leaving group of N-aroyl β-lactams increase the rate of alkaline hydrolysis and give a Bronsted βIg of -0.55, indicative of a late transition state for rate-limiting formation of the tetrahedral intermediate. Interestingly, the corresponding Bronsted βIg for the β-lactamase-catalyzed hydrolysis of the same substrates is -0.06, indicative of an earlier transition state for the enzyme-catalyzed reaction. By contrast, although the Bronsted βIg for the alkaline hydrolysis of N-aroyl β-sultams is -0.73, similar to that for the β-lactams, that for the sulfonylation of β-lactamase by these compounds is -1.46, compatible with significant amide anion expulsion/S-N fission in the transition state. In this case, the enzyme reaction displays a later transition state compared with hydroxide-ion-catalyzed hydrolysis of the β-sultam.
