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Synthesis and Enantiomeric Selectivity of Chiral Crown Ethers.-Condensation of L-tartaric acid-derived dioxolanes (I) with various polyethylene glycol ditosylates provides access to crown ethers containing two (III) or four stereocenters (IV). The enantioselectivity in complexing L-or D-valine methyl ester is studied using potentiometry. An inversion of stereoselectivity in complexation is observed with growing ring size of the crown ethers. -(LUK'YANENKO, N. G.; LOBACH, A. V.; LEUS, O. N.; TITOVA, N. YU.; Russ.

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Synthesis and Enantiodifferentiating Properties of Chiral Aza Crown Ethers. -The synthesis of a series of chiral mono-and diaza crownethers, e.g., (I) and (II), is described. All the examined aza crown ethers react preferentially with L-valine, their enantioselectivity is considerably higher than that of the corresponding oxygen analogues. -(LOBACH, A. V.; LEUS, O. N.; TITOVA, N. Y.; LUK'YANENKO, N. G.; Russ.