GR 24 enantiomers: Synthesis, NMR spectroscopy, X-ray crystallography, andseparation by chiral electrokinetic capillary chromatography

Chiral discrimination of enantiomers of 2-methyl-4-(2-oxo-2,3,3a, 8b-tehahy dro-4H-indeno[1,2b]furan-3-yl-idenemethoxy)but-2-en-4-olide (commonly refer red to as GR 24) by three polymeric chiral surfactants (PCS) is studied by use of chiral polymeric surfactant capillary electrophoresis (PSCE), The CP SCE results indicate that the optical configurations of valine residues on the PCS backbone affect chiral resolution and elution order of GR24 stereoi somers. The L- and D-forms of poly(sodium N-undecanoyl valinate) provide ba seline separation of all four enantiomers while the DL-form separates diast ereomers of GR 24 (1). A model is presented rationalizing the migration beh avior and chiral resolution of 1 in CPSCE, The actual configuration of the stereogenic centers of GR 24 and 3-[(2,5-dihydro-3-methyl-2-oxo-5-furanyl)o xo]- methylene-3,3a,6,6a-tetratrahydro-2H-cyclopenta[b]furan-2-one (GR 7) i s established by a concerted application of high-resolution nuclear magneti c resonance spectroscopy and X-ray crystallography.