Effective resolution of chiral 1,1':5',1"-ternaphthalene-2,2',6',2"-tetrol through camphorsulfonylation, recrystallization and reductive desulfonylation

Optical resolution of the title compound, TERNOL (1), having bis-bidentate sites of axial chiralities was succesful. A racemic mixture of 1 was converted to the tetracamphorsulfonate 2 in high yield, and a single recrystallization of 2 under kinetic conditions effectively separated the diastereomers. The crystal part obtained in 44% yield consisted of (S,S)-2 of 96% diastereomer excess (de), and the solution part (50% yield) contained (R,R)-2 of 96% de. An additional recrystallization of the each part resulted in diastereomerically pure 2 in high yield. Hydride reduction of the ketones in the camphorsulfonyl groups of 2 caused smooth intramolecular transesterification, and enantiomerically pure (R,R)-1 and (S,S)-1 were obtained in good yields.