Enantioseparation of racemic organic ammonium perchlorates by a silica gelbound optically active di-tert-butylpyridino-18-crown-6 ligand

Both enantiomers of the novel chiral di-tert-butylpyridino-18-crown-6 ligan d (R,R)-7 and (S,S)-7 containing an allyloxy group on the pyridine subcycli c unit were prepared by the reaction of 4-allyloxy-2,6-pyridinedimethyl dit osylate 9 and the enantiomers of di-tert-butyl-substituted tetraethylene gl ycol (R,R)-8 and (S,S)-8 in the presence of a strong base. One of them, (R, R)-7, was covalently attached to silica gel, and this chiral stationary pha se (CSP) separated four selected racemic organic ammonium perchlorates into their enantiomers by column chromatography. (C) 1999 Elsevier Science Ltd. All rights reserved.