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Enabling Direct Preferential Crystallization in a Stable Racemic Compound System.

Lina C Harfouche1, Clément Brandel1, Yohann Cartigny1

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Molecular Pharmaceutics
|September 24, 2019
PubMed
Summary

Preferential crystallization (PC) successfully resolved proxyphylline, a stable racemic compound, by using a solvent with low nucleation rates. This method enables broader applications of PC for slowly crystallizing compounds.

Keywords:
metastable conglomeratenucleation inhibitionpreferential crystallizationproxyphylline

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Area of Science:

  • Chemical Engineering
  • Crystallization Science

Background:

  • Preferential crystallization (PC) is a method for separating enantiomers.
  • Proxyphylline forms a stable racemic compound, posing challenges for separation.
  • Slow nucleation rates are critical for successful PC of challenging compounds.

Purpose of the Study:

  • To achieve preparative resolution of proxyphylline using preferential crystallization.
  • To investigate the feasibility of PC for compounds forming stable racemic compounds.
  • To identify suitable solvent conditions that promote slow nucleation.

Main Methods:

  • Solvent screening and selection based on nucleation rate.
  • Induction time measurements to quantify nucleation kinetics.
  • Implementation of isothermal and polythermic preferential crystallization modes.
  • Seeding with pure enantiomer to induce crystallization.

Main Results:

  • Preferential crystallization of proxyphylline was successfully achieved.
  • Isobutyl alcohol demonstrated a low nucleation rate, allowing for a 1-hour induction time at high supersaturation (β = 2.3).
  • Both isothermal and polythermic PC modes were effective.
  • The study demonstrates PC's applicability to slowly crystallizing racemic compounds.

Conclusions:

  • Preferential crystallization is a viable method for resolving proxyphylline.
  • Careful solvent selection is key to overcoming challenges posed by stable racemic compounds.
  • This work expands the scope of PC applications to include slowly crystallizing racemates.