A mixture of
58.5 g. (0.5 mole) of acetylglycine (p. 11) (Note
1),
30 g. (0.37 mole) of anhydrous sodium acetate,
79 g. (0.74 mole) of freshly distilled benzaldehyde, and
134 g. (1.25 moles) of 95 per cent acetic anhydride in a
loosely corked 1-l. Erlenmeyer flask is warmed on the
steam bath with occasional stirring until solution is complete (ten to twenty minutes). The resulting solution is boiled for one hour under reflux, cooled, and placed in a
refrigerator overnight. The solid mass of yellow crystals is treated with 125 cc. of cold water and broken up with a
stirring rod. The crystals are then transferred to a
Büchner funnel and washed thoroughly with cold water (Note
2). After being dried in a
vacuum desiccator over
phosphorus pentoxide and potassium hydroxide, the crude azlactone weighs
69–72 g. (
74–77 per cent of the theoretical amount). The product melts at
148–150°, and is sufficiently pure for preparative purposes (Note
3).
In a
1-l. round-bottomed, short-necked flask 47 g. (0.25 mole) of the crude azlactone of α-acetaminocinnamic acid is dissolved by boiling with a mixture of
450 cc. of acetone and 175 cc. of water. Hydrolysis is completed by boiling under reflux for four hours. Most of the
acetone is then removed by distillation at ordinary pressure on a steam bath. The residual solution is diluted with 400 cc. of water, heated to boiling for five minutes to ensure complete solution of the acetamino acid, and filtered (Note
4) and (Note
5). A small amount of undissolved material (
0.2–0.5 g.) which remains on the filter is washed with 50–75 cc. of boiling water. Any crystals which separate from the filtrate are redissolved by heating, after which the solution is boiled for five minutes with
10 g. of Norite and filtered with the aid of gentle suction while still almost at the boiling point (Note
5). The
Norite is washed thoroughly on the funnel with two to four 50-cc. portions of boiling water to remove the crystals which separate during the filtration, and the washings are added to the main filtrate. After standing in a refrigerator overnight the colorless, crystalline needles are collected on a
Büchner funnel (Note
6), washed with 150–200 cc. of ice-cold water, and dried for several hours at 90–100°. The yield is
41–46 g. (
80–90 per cent of the theoretical amount) of practically pure material, m.p.
191–192° (Note
7).