9341. 2-Thiolhistidine

Nomenclature

CAS number: 13552-61-9
α-Amino-2,3-dihydro-2-thioxo-1H-imidazole-4-propanoic acid; 2-mercaptohistidine; α-amino-2-mercapto-4-imidazolepropionic acid.
C6H9N3O2S; mol wt 187.22.
C 38.49%, H 4.85%, N 22.44%, O 17.09%, S 17.13%.

Description and references

Prepn from histidine: Ashley, Harington, J. Chem. Soc. 1930, 2586; from aspartic acid: Harington, Overhoff, Biochem. J. 27, 338 (1933). Alternate procedures: Hegedüs, Helv. Chim. Acta 38, 22 (1955); Marei, Raphael, J. Chem. Soc. 1958, 2624. Review: J. P. Greenstein, M. Winitz, Chemistry of the Amino Acids vol. 3 (John Wiley, New York, 1961) pp 2671-2675.

Chemical structure

Derivative

l-Form.

Properties

Plates from water, darkens at 290°, not melted at 310°. [α]D20 10° (c = 2 in N HCl). pK11 1.84; pK21 8.47; pK31 11.4. Readily sol in hot water, sparingly sol in water at room temp. Tends to form supersaturated solns. Practically insol in alcohol, other organic solvents.

Derivative

Dihydrochloride.
C6H9N3O2.2HCl; mol wt 228.08.
C 31.60%, H 4.86%, N 18.42%, O 14.03%, Cl 31.09%.

Properties

Large prisms, dec 197-199°. Freely sol in water, sparingly sol in alcohol.