Pharmaceutical Research

, Volume 21, Issue 9, pp 1708–1717 | Cite as

Early Prediction of Pharmaceutical Oxidation Pathways by Computational Chemistry and Forced Degradation

  • Darren L. Reid
  • C. Jeffrey Calvitt
  • Mark T. Zell
  • Kenneth G. Miller
  • Carol A. Kingsmill


Purpose. To show, using a model study, how electronic structure theory can be applied in combination with LC/UV/MS/MS for the prediction and identification of oxidative degradants.

Methods. The benzyloxazole 1, was used to represent an active pharmaceutical ingredient for oxidative forced degradation studies. Bond dissociation energies (BDEs) calculated at the B3LYP/6-311+G(d,p)//B3LYP/6-31G(d) level with isodesmic corrections were used to predict sites of autoxidation. In addition, frontier molecular orbital (FMO) theory at the Hartree-Fock level was used to predict sites of peroxide oxidation and electron transfer. Compound 1 was then subjected to autoxidation and H2O2 forced degradation as well as formal stability conditions. Samples were analyzed by LC/UV/MS/MS and degradation products proposed.

Results. The computational BDEs and FMO analysis of 1 was consistent with the LC/UV/MS/MS data and allowed for structural proposals, which were confirmed by LC/MS/NMR. The autoxidation conditions yielded a number of degradants not observed under peroxide degradation while formal stability conditions gave both peroxide and autoxidation degradants.

Conclusions. Electronic structure methods were successfully applied in combination with LC/UV/MS/MS to predict degradation pathways and assist in spectral identification. The degradation and excipient stability studies highlight the importance of including both peroxide and autoxidation conditions in forced degradation studies.

forced degradation oxidation mass spectrometry computational pharmaceutical 


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  1. 1.
    K. A. Alsante, L. Martin, and S. W. Baertschi. A stress testing benchmarking study. Pharm. Tech. 2:60-72 (2003).Google Scholar
  2. 2.
    PP. Crowley and L. Martini. Drug-EXCIPIENT INTERACTIONS. Pharm. Technol. Eur. 13:26-34 (2001).Google Scholar
  3. 3.
    K. A. Alsante and T. Hatajik. Purposeful Degradation Best Practice Guidance Document for Exploratory Development Compounds, internal document, Pfizer Inc., Degradation Resource Group (1999).Google Scholar
  4. 6.
    K. C. Waterman, R. C. Adami, K. A. Alsante, J. Hong, M. S. Landis, F. Lombardo, and C. J. Roberts. Stablization of pharmaceuticals to oxidative degradation. Pharm. Develop. Tech. 7:1-32 (2002).Google Scholar
  5. 7.
    S. W. Hovorka and C. Schöniech. Oxidative degradation of pharmaceuuticals: theory, mechanisms and inhibition. J. Pharm. Sci. 90:253-269 (2001).Google Scholar
  6. 8.
    P. Gamache, R. McCarthy, J. Waraska, and I. Acworth. Pharmaceutical oxidative stability profiling with high-throughput voltammetry. Am. Lab. 6:21-25 (2003).Google Scholar
  7. 9.
    Arvi Rauk. Orbital Interaction Theory of Organic Chemistry, 2nd ed., John Wiley & Sons, New York, 2001.Google Scholar
  8. 10.
    C. von Sonntag. The Chemical Basis of Radiation Biology, Taylor and Francis, London, 1987.Google Scholar
  9. 11.
    G. S. Hammond. A correlation of reaction rates. J. Am. Chem. Soc. 77:334-338 (1955).Google Scholar
  10. 12.
    M. Jonsson, D. D. M. Wayner, D. A. Armstrong, D. Yu, and A. Rauk. On the thermodynamics of peptide oxidation: anhydrides of glycine and alanine, J. Chem. Soc. Perkin Trans. 2:1967-1972 (1998).Google Scholar
  11. 13.
    K. G. Liu, M. H. Lambert, A. H. Ayscue, B. R. Henke, L. M. Leenitzer, W. R. Oliver Jr., K. D. Plunket, H. E. Xu, D. D. Sternbach, and T. M. Willson. Synthesis and biological activity of L-tyrosine-based PPAR_ agonists with reduced molecular weight. Bioorg. Med. Chem. Lett. 11:3111-3113 (2001).Google Scholar
  12. 14.
    Spartan'02, Wavefunction, Inc., Irvine, CA.Google Scholar
  13. 15.
    A. P. Scott and L. Radom. Harmonic vibrational frequencies: an evaluation of hartree-fock, møller-plesset, quadratic configuration interaction, density functional theory, and semiempirical scale factors. J. Phys. Chem. 100:16502-16513 (1996).Google Scholar
  14. 16.
    N. Kobko and J. J. Dannenberg. Effect of basis set superposition error (BSSE) upon ab initio calculations of organic transition states. J. Phys. Chem. A 105:1944-1950 (2001).Google Scholar
  15. 17.
    W. J. Hehre, R. Ditchfield, L. Radom, and J. A. Pople. Molecular orbital theory of the electronic structure of organic compounds. V. Molecular theory of bond separation. J. Am. Chem. Soc. 92: 4796-4816 (1970).Google Scholar
  16. 18.
    D. A. Armstrong, D. Yu, and A. Rauk. Oxidative damage to the glycyl α-carbon site in proteins: an ab initio study of the C-H bond dissociation energy and the reduction potential of the C-centered radical. Can. J. Chem. 74:1192-1199 (1996).Google Scholar
  17. 19.
    M. Jonsson, D. M. Wayner, D. A. Armstrong, D. Yu, and A. Rauk. On the thermodynamics of peptide oxidation: anhydrides of glycine and alanine, J. Chem. Soc. Perkin Trans. 2:1967-1972 (1998).Google Scholar
  18. 20.
    E. J. Prosen, R. Gilmont, and F. D. Rossini. Heats of combustion of benzene, toluene, ethyl-benzene, o-xylene, m-xylene, p-xylene, n-propylbenzene, and styrene. J. Res. NBS 34:65-70 (1945).Google Scholar
  19. 21.
    S. Soonho, D. M. Golden, R. K. Hanson, and C. T. Bowman. A shock tube study of benzylamine decomposition: overall rate coefficient and heat of formation of the benzyl radical. J. Phys. Chem. A 106:6094-6098 (2002).Google Scholar
  20. 22.
    J. D. Cox, D. D. Wagman, and V. A. Medvedev. CODATA Key Values for Thermodynamics, Hemisphere Publishing Corp., New York, 1984, p. 1.Google Scholar
  21. 23.
    S. Furuyama, D. M. Golden, and S. W. Benson. Thermochemistry of the gas phase equilibria i-C3H7I = C3H6 + HI, n-C3H7I = i-C3H7I, and C3H6 + 2HI = C3H8 + I2. J. Chem. Thermodyn. 1:363-375 (1969).Google Scholar
  22. 24.
    J. R. Lacher, C. H. Walden, K. R. Lea, and J. D. Park. Vapor phase heats of hydrobromination of cyclopropane and propylene. J. Am. Chem. Soc. 72:331-333 (1950).Google Scholar
  23. 25.
    W. Tsang. Heats of formation of organic free radicals by kinetic methods in Energetics of Organic Free Radicals, J. A. Martinho Simoes, A. Greenberg, J. F. Liebman, Blackie Academic and Professional, London, 1996, pp. 22-58.Google Scholar
  24. 26.
    J. Hine and K. Arata. Keto-Enol tautomerism. II. The calori-metrical determination of the equilibrium constants for keto-enol tautomerism for cyclohexanone. Bull. Chem. Soc. Jpn. 49:3089-3092 (1976).Google Scholar
  25. 27.
    J. H. S. Green, Revision of the values of the heats of formation of normal alcohols, Chem. Ind. (London) 1215-1216 (1960).Google Scholar
  26. 28.
    D. A. Block, D. A. Armstrong, and A. Rauk. Gas phase free energies of formation and free energies of solution of C-centered free radicals from alcohols: a quantum mechanical-Monte Carlo study. J. Phys. Chem. A 103:3562-3568 (1999).Google Scholar
  27. 29.
    D. A. McQuarrie. Statistical Thermodynamics; Harper & Row: New York, NY, 1973.Google Scholar
  28. 30.
    J. W. Ochterski. Thermochemistry in Gaussian ©2000 Technical paper, Gaussian, Inc. help@gaussian.comGoogle Scholar
  29. 31.
    S. Smallcombe, S. Patt, and P. Keifer. WET solvent suppression and its applications to LC NMR and high-resolution NMR spectroscopy. J. Magn. Reson. A 117:295-303 (1995).Google Scholar
  30. 32.
    P. Crowley and L. Martini. Drug-excipient interactions. Pharm. Technol. Eur. 13:26-34 (2001).Google Scholar
  31. 33.
    F. G. Bordwell, X. M. Zhang, and M. S. Alnajjar. Effects of adjacent acceptors and donors on the stabilities of carbon-centered radicals. J. Am. Chem. Soc. 114:7623-7629 (1992).Google Scholar
  32. 34.
    R. A. Jones and G. P. Bean. The Chemistry of Pyrroles. Academic Press. New York 34:209-247 (1977).Google Scholar
  33. 35.
    A. Gossauer and P. Nesvadba. Reactivity of the 1H-pyrrole ring system. Oxidation and reduction of the pyrrole ring. In Chemistry of Heterocyclic Compounds, Pyrroles, Pt. 1, Chichester. United Kingdom 48:499-536 (1990).Google Scholar
  34. 36.
    J. Bordner and H. Rapoport. Synthesis of 2,2'-bipyrroles from 2-pyrrolinones. J. Org. Chem. 30:3824-3828 (1965).Google Scholar
  35. 37.
    E. B. Smith and H. B. Jensen. Autoxidation of three 1-alkylpyr-roles. J. Org. Chem. 32:3330-3334 (1967).Google Scholar
  36. 38.
    G. Boccardi. Autoxidation of drugs: prediction of degradation impurties from results of reaction with radical chain initiators. Farmaco 49:431-435 (1994).Google Scholar

Copyright information

© Springer Science+Business Media, Inc. 2004

Authors and Affiliations

  • Darren L. Reid
    • 1
  • C. Jeffrey Calvitt
    • 1
  • Mark T. Zell
    • 1
  • Kenneth G. Miller
    • 1
  • Carol A. Kingsmill
    • 1
  1. 1.Analytical Research and DevelopmentPharmaceutical Sciences, Pfizer Global Research and DevelopmentAnn ArborUSA

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