5451. Leucine

Nomenclature

CAS number: 61-90-5
l-Leucine; Leu; L; 2-amino-4-methylvaleric acid; α-aminoisocaproic acid; (S)-2-amino-4-methylpentanoic acid.
C6H13NO2; mol wt 131.17.
C 54.94%, H 9.99%, N 10.68%, O 24.39%.

Description and references

An essential amino acid for human development. Discovery of leucine is attributed to Proust in 1819 who reported its separation from fermented milk curds. Early chemistry and biochemistry: Amino Acids and Proteins, D. M. Greenberg, Ed. (Charles C. Thomas, Springfield, IL, 1951) 950 pp., passim; J. P. Greenstein, M. Winitz, Chemistry of the Amino Acids vols 1-3 (John Wiley and Sons, Inc., New York, 1961) pp. 2075-2096, passim. Chromatographic determn of specific activity in biological fluids: E. P. Donahue et al., J. Chromatogr. 571, 29 (1991); separation of isotopes: P. Q. Baumann et al., ibid. 573, 11 (1992). Metabolism in humans: K. J. Motil et al., Metabolism 30, 783 (1981); in children receiving parenteral nutrition: O. Goulet et al., Am. J. Physiol. 265, E540 (1993). Kinetics modelling in humans: C. Cobelli et al., ibid. 261, E539 (1991).

Chemical structure

Properties

White glistening hexagonal plates from aq alc. d18 1.293. Sublimes at 145-148°. Dec 293-295° (rapid heating, sealed tube). [M]D +21.0° (5N HCl); [M]D +29.5° (glacial acetic acid). [α]D25 10.8° (c = 2.2); [α]D26 +15.1° in 6N HCl (38 mols HCl per mol leucine); [α]D20 +7.6° in 3N NaOH (30 mols NaOH per mol leucine). Rf value 0.79. Soly in water (g/l): 22.7 (0°); 24.26 (25°); 28.87 (50°); 38.23 (75°); 56.38 (100°); in 99% alcohol: 0.72; in acetic acid: 10.9. Insol in ether.

Derivative

dl-Form.

Properties

Leaflets fom water. Sweet taste. Dec 332° (also reported as 290°). Sublimes. pK1 2.36; pK2 9.60. Soly in water (g/l): 7.97 (0°); 9.91 (25°); 14.06 (50°); 22.76 (75°); 42.06 (100°); in 90% alcohol: 1.3. Insol in ether.

Derivative

Hydrochloride.
C6H13NO2.HCl; mol wt 167.63.
C 42.99%, H 8.42%, N 8.36%, O 19.09%, Cl 21.15%.

Properties

Crystals. Freely sol in water.

Use

Nutrient.