Title: Hydroxyproline
CAS Registry Number: 51-35-4
CAS Name: (4R)-4-Hydroxy-L-proline
Additional Names: Hyp; Ls-hydroxyproline; (-)-(2S,4R)-4-hydroxyproline; trans-4-hydroxyproline; 4(R)-hydroxy-2(S)-pyrrolidinecarboxylic acid
Molecular Formula: C5H9NO3
Molecular Weight: 131.13
Percent Composition: C 45.80%, H 6.92%, N 10.68%, O 36.60%
Literature References: Amino acid analog of proline, q.v.; non-essential for human development. Shows cis-trans isomerism. Constituent of collagen, q.v. Isoln from gelatin: E. Fischer, Ber. 35, 2660 (1902). Synthesis: H. Leuchs, Ber. 38, 1937 (1905); and structure determn: H. Leuchs, J. F. Brewster, Ber. 46, 986 (1913). Stereochemistry: Hudson, Neuberger, J. Org. Chem. 15, 24 (1950). 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. 2018-2042, passim. Flow sheets of four different syntheses: Chem. Eng. News 40, 40 (Nov. 12, 1962). One pot synthesis: S. G. Ramaswamy, E. Adams, J. Org. Chem. 42, 3440 (1977). Proof of occurence in plants: D. Ashford, A. Neuberger, Trends Biochem. Sci. 5, 245 (1980). Effects of cis-trans isomerism on protein structure: N. Panasik, Jr. et al., Int. J. Pept. Protein Res. 44, 262 (1994). Review: R. Kuttan, A. N. Radhakrishnan, Adv. Enzymol. 37, 273-348 (1973). Review of metabolism: E. Adams, L. Frank, Annu. Rev. Biochem. 49, 1005-1061 (1980).
Properties: Rhombs or needles from water, mp 274°. [a]D -76.5° (c = 2.5 in water). pK1¢ 1.82; pK2¢ 9.65. Soly in water at 0°: 288.6 g/l; at 25°: 361.1 g/l; at 50°: 451.8 g/l; at 65°: 516.7 g/l. Very slightly sol in alcohol. Insol in ether.
Melting point: mp 274°
pKa: pK1¢ 1.82; pK2¢ 9.65
Optical Rotation: [a]D -76.5° (c = 2.5 in water)
Derivative Type: cis-Form
CAS Registry Number: 618-27-9
Additional Names: Allohydroxyproline; (2S,4S)-4-hydroxyproline
Properties: mp 238-241°. [a]D18 -58.1° (c = 5.2 in water).
Melting point: mp 238-241°
Optical Rotation: [a]D18 -58.1° (c = 5.2 in water)
Hydroxypropyl Cellulose Hydroxypropyl Methylcellulose Hydroxystilbamidine Hydroxystreptomycin Hydroxytetracaine

Hydroxyproline structure.svg
CAS number 51-35-4 YesY
PubChem 825
ChemSpider 236516 YesY
MeSH Hydroxyproline
Jmol-3D images Image 1
Molecular formula C5H9NO3
Molar mass 131.13 g·mol−1
 YesY (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

(2S,4R)-4-Hydroxyproline, or L-hydroxyproline (C5H9O3N), is a common non-proteinogenic amino acid, abbreviated as HYP, e.g., in Protein Data Bank.