Enantiopure Aromatic Saddles Bearing the Fenestrindane Core

The synthesis of enantiomerically pure, configurationally stable fenestrindane-based polyaromatic compounds with saddle-like structures is reported. Seven racemic fenestrane synthetic precursors were first screened by chiral HPLC for resolvability into enantiomers. Among the three resolvable precursors, a tribenzofenestrene derivative was resolved on a semipreparative scale, and the absolute configuration of the more slowly eluting enantiomer was established by X-ray crystallography. The enantiopure tribenzofenestrenes were then separately converted, in six steps, to the saddle-shaped fenestrindane derivatives in optically pure form. The two enantiomeric pairs of saddles were characterized by H-1 and C-13 NMR spectroscopy, mass spectrometry, and circular dichroism spectroscopy. All new compounds reported herein represent the first enantiopure non-natural carbocyclic fenestranes isolated to date.