Bilopaque,Winthrop,US,1972
A solution of 5.0 g of α-ethyl-β-(aminophenyl)propionic acid in 100 ml of
water containing 5 ml of concentrated hydrochloric acid was added over a
period of ? hour to a stirred solution of 3.2 ml of iodine monochloride in 25
ml of water and 25 ml of concentrated hydrochloric acid heated to 60°C. After
addition was complete, the heating was continued for ? hour longer at 60° to
70°C. A black oil separated which gradually solidified. The mixture was then
cooled and sodium bisulfite was added to decolorize. Recrystallization of the
product from methanol gave about 8 g of α-ethyl-β-(2,4,6-triiodo-3-
aminophenyl)-propionic acid, MP 147° to 150°C. The product could be further
purified by precipitation of its morpholine salt from ether solution and
regeneration of the free amino acid by treatment of a methanol solution of the
morpholine salt with sulfur dioxide. The pure amino acid had the MP 155° to
156.5°C (corr).
A mixture of 57.1 g (0.1 mol) of α-ethyl-β-(3-amino-2,4,6-
triiodophenyl)propionic acid, 250 ml of butyric anhydride and 1 ml of 70%
perchloric acid was heated at 105°C for 5 hours. After cooling, the reaction
mixture was poured onto ice, diluted to a volume of 3 liters with water, and
heated on a steam bath with addition of solid sodium carbonate to keep the
mixture basic. After all the excess butyric anhydride had been hydrolyzed, the
mixture was made acid with dilute hydrochloric acid, the aqueous layer
decanted from the resulting gummy solid, and the latter was then washed
several times with water. The product was dissolved in acetic acid, decolorized
with activated charcoal, and the solution while hot diluted with water to the point of turbidity. The product was collected by filtration and dried, giving 40 g
of α-ethyl-β-(3-dibutyramido-2,4,6-triiodophenyl)propionic acid, MP 166° to
169.5°C (corr.) when recrystallized from acetic acid. Reaction with sodium
hydroxide gives the final product.
