BrNC(=O)[CH2:4][CH2:5][C:6]([NH2:8])=O.[NH:10]=[N:11][CH:12]=NN.[CH2:15](O)[CH2:16]CC.C(O)(=[O:22])C.CO.[OH2:26]>C(OCC)(=O)C.O>[N+:8]([C:6]1[CH:16]=[CH:15][C:12]([NH:11][NH2:10])=[CH:4][CH:5]=1)([O-:22])=[O:26]Next 300 mg of N-bromosuccinamide was added to 1.5 g of the formazan derivative in 200 ml ethyl acetate. After reaction for 0.5 hour under reflux conditions, the product tetrazolium salt was recovered by precipitation with ether as a yellow powder. It was purified by recrystallization from acetone-methanol after charcoal treatment of the hot solution, by pouring the hot filtrate solution into ether. The crystals were collected and dried in vacuum yielding 0.6 g. Based upon the expected formula of C19H11BrIN7O6, the expected elemental analysis is 35.65% C, 1.73% H, 15.32% N and 15% O. Observed were 35.9%, 2.03%, 12.42% and 16.67%, respectively. The product showed a melting point over the 210-217 degree centigrade range, indicating greater than 98% purity. Thin layer chromatography (n-butanol:acetic acid:water at a 78:5:17 volume ratio) showed a single spot with a retention factor of 0.73. U.V. analysis in methanol:water (1:1 by volume) showed a maximum lambda at 240.5 nm and a molar extinction coefficient of 28,600.
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