24.8 g of 4,4'-diaminodiphenyl sulfone, 150 g of methyl chloroacetate and 150
ml of ethanol are refluxed together and refluxed for 24 hours. The alcohol and
excess methyl chloroacetate are then distilled off on a steam bath under
reduced pressure. The residue consisting of the hydrochloride salt of 4-amino-
4'-(carbomethoxymethylamino)diphenyl sulfone is mixed with of alcoholic
solution containing 2.5 g lithium hydroxide and refluxed for 4 hours on the
steam bath. Most of the alcohol is removed by distillation and the residual
lithium salt of 4-amino-4'-(carboxymethylamino)diphenyl sulfone taken up
water. The solution is filtered and dilute HCl added until no more separation
occurs. The 4-amino-4'-(carboxymethylamino)diphenyl sulfone thus obtained
is collected and dried.
The sodium salt of 4-amino-4'-(carboxymethylamino)diphenyl sulfone is
prepared by dissolving the free acid in an aqueous solution containing one
equivalent of sodium hydroxide and evaporating the solution to dryness in
vacuo.
