DOLPHIN. Can. J. Chem. 53, 1554 (1975.The sulfonation of meso-tetraphenylporphyrin, in concentrated sulfuric acid followed by neutralization and dialysis, provides an efficient and convenient route to meso-tetra(4-sulfonatopheny1)porphyrin. The initial studies by Winkelman (1) on the localization of meso-tetra(4-sulfonatopheny1)-porphyrin in tumors have been followed by an increasing interest in this water soluble porphyrin. This interest has been stimulated by the ready availability (2) of meso-tetraphenylporphyrin (TPP) 1 and its conversion into mesotetra(4-sulfonatopheny1)porphyrin 2 by direct sulfonation.Two methods for this sulfonation have recently been reported. Both methods bring about the sulfonation in hot sulfuric acid and differ only in the isolation and purification of the product. The method developed by Fleischer et al. (3) invokes preparation of the tetraammonium salt which is purified by six precipitations from methanol-acetone but, in our hands, a good recovery of the product always results in its contamination with ammonium sulfate. To remove the inorganic salts one must sacrifice large amounts of the product at each stage with a resultant poor yield.The second method reported by Srivastava and Tsutsui (4) requires dilution of the reaction 'Author to whom correspondence should be addressed. mixture and addition of lime to the resulting large volume of aqueous solution in order to remove the sulfuric acid as calcium sulfate. A number of time-consuming and cumbersome filtrations and concentrations are then required to isolate the product, which is always contaminated with inorganic salts unless careful precautions are taken, which again result in a lowering of the yield.We wish to report here the preparation and simplified purification procedure which involves dialysis to remove inorganic contaminants and results in a 7574 overall yield from TPP. For personal use only.
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