Solid state properties and effective resolution procedure for guaifenesin, 3-(2-methoxyphenoxy)-1,2-propanediol

Racemic expectorant guaifenesin, 3-(2-methoxyphenoxy)-1,2-propanediol 2 undergoes spontaneous resolution upon crystallization. This fact is confirmed by thermal analysis (single eutectic V-shape binary melting phase diagram, adequate entropy and free energy characteristics). Racemic 2 could be effectively resolved into (S)- and (R)-2 by a preferential crystallization procedure. Single enantiomer drugs levomoprolol and levotensin were obtained by starting from enantiomeric 2 through the sulfite route.

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(S)-3-(2-Methoxyphenoxy)-propane-1,2-diolC10H14O4Ee >99% [by thermal analysis][α]D20=+9.5 (c 1.0, anhydrous MeOH)[α]D20=+11.7 (c 1.0, anhydrous EtOH)[α]D20=+15.0 (c 1.0, rectified EtOH)Initial source of chirality: (S)-3-chloropropane-1,2-diolSubsequent source of chirality: spontaneous resolutionAbsolute configuration: (S)