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Org. Synth. 1925, 4, 3
DOI: 10.15227/orgsyn.004.0003
α-AMINO-n-CAPROIC ACID
[Norleucine]
Submitted by C. S. Marvel and V. du Vigneaud.
Checked by H. T. Clarke and E. R. Taylor.
1. Procedure
In a 1-l. round-bottomed flask is placed 760 g. (844 cc.) of concentrated aqueous ammonia (sp. gr. 0.9) and to this is slowly added 150 g. (0.77 mole) of α-bromocaproic acid (Note 1). The flask is well stoppered and allowed to stand in a warm place (50-55°) for twenty to thirty hours. The amino acid separates and is filtered off with suction and washed with methyl alcohol (Note 2). This crop of crystals weighs 51–56 g. The aqueous filtrate is evaporated nearly to dryness on a steam bath and then treated with about 250 cc. of methyl alcohol. This precipitates a second crop of amino acid contaminated with ammonium bromide. On washing with methyl alcohol and recrystallizing from water, there is obtained 10–15 g. more of pure product. The total yield is 63–68 g. (62–67 per cent of the theoretical amount).
2. Notes
1. The once-distilled bromocaproic acid (p. 115) is satisfactory.
2. If the amino acid is not carefully washed with alcohol, it contains ammonium bromide and may possess an objectionable odor. Methyl alcohol is preferable to ethyl alcohol since it dissolves ammonium bromide more readily.
3. Discussion
α-Amino-n-caproic acid can be prepared by the action of ammonia on α-bromo-n-caproic acid,1 and by the alkylation with butyl bromide of benzoylaminomalonic ester with subsequent hydrolysis.2

References and Notes
  1. Hüfner, J. prakt. Chem. (2) 1, 7 (1870); Fischer, Ber. 33, 2381 (1900); Abderhalden, Froehlich and Fuchs, Z. physiol. Chem. 86, 456 (1913); Adams and Marvel, J. Am. Chem. Soc. 42, 320 (1920); E. I. du Pont de Nemours & Co., U. S. pat. 2,109,929 [C. A. 32, 3424 (1938)].
  2. Painter, J. Am. Chem. Soc. 62, 232 (1940).

Appendix
Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)

benzoylaminomalonic ester

ethyl alcohol,
alcohol (64-17-5)

ammonia (7664-41-7)

methyl alcohol (67-56-1)

ammonium bromide (12124-97-9)

Butyl bromide (109-65-9)

Norleucine (327-57-1)

α-Bromocaproic acid,
α-bromo-n-caproic acid (616-05-7)

bromocaproic acid (4224-70-8)

α-AMINO-n-CAPROIC ACID (616-06-8)