A mixture of equimolecular amounts of m-nitraniline (69.0 g), methacrylic
acid (43.0 g), and pyridine (39.5 g) was heated to 125°C for 20 h, and was
then poured into 500 ml water. A semi-crystalline product separated from the
liquid. The supernatant liquid was decanted and 500 ml fresh water was
added. The pH was adjusted to 7-7.5 by means of sodium hydroxide. The
precipitate was filtered with suction and washed with water. When the filtrate
was acidified with acetic acid, a precipitate of N-(3-nitrophenyl)-β-aminoisobutyric acid was formed. When filtered, washed with water and dried, it
weighed 56.0 g and had a melting point of 130°-131°C (recryst. from
alcohol). The yield was 50% based on nitraniline.
0.25 mol (56.0 g) N-(3-nitrophenyl)-β-aminoisobutyric acid, prepared as
described above, 160 ml glacial acetic acid, and 40 ml acetic anhydride were
heated 48 h to 50°C, and the reaction mixture was poured into 600 ml water.
A crystalline precipitate of N-acetyl-N-(3-nitrophenyl)-β-aminoisobutyric acid
formed gradually. When recovered, it weighed 56.0 g (84% yield). Melting
point 146°-148°C.
100.0 g N-acetyl-N-(3-nitrophenyl)-β-amino-isobutyric acid were dissolved in
1 L water and 40 ml 25% aqueous ammonia, and the solution was
hydrogenated in the presence of about 10.0 g Raney nickel at 20°C and about
450 p.s.i. until the pressure drop indicated the complete conversion of the
NO2 groups to NH2. Thus N-acetyl-N-(3-aminophenyl)-β-amino-isobutyric acid
was obtained.
The solution of N-acetyl-N-(3-aminophenyl)-β-amino-isobutyric acid was
filtered after standing overnight, mixed with an equal volume of acetic acid,
and there after with a solution of 275.0 g iodine monochloride and 200.0 g
sodium chloride in 1 L water. The mixture was kept at 50°C with stirring for
48 h. Light brown crystals of crude N-acetyl-N-(2,4,6-triiodo-3-aminophenyl)-
β-amino-isobutyric acid precipitated, were filtered off, washed with water, and
dried. They weighed 195.0 g (84.5% yield based on N-acetyl-N 3-nitrophenylp-amino-isobutyric acid).
