Macromolecular ionophores. 1. Chiral recognition properties of poly[(1→6)-2,5-anhydro-D-glucitol] toward racemic amino acid ester

The chiral recognition property of poly(1→6)-2,5-anhydro-3,4-di-O-alkyl-D-glucitol] ( 1 ) toward racemic RCH (CO₂CH₃)NH₃⁺ · PF₆^? ( 2 · HPF₆) has been studied using a transport system involving an aqueous source and receiving phases separated by a chloroform phase containing 1 . Transport rates for aromatic guests 2a (R = Ph) and 2b (R = CH₂Ph) were faster than those for aliphatic guests, 2c (R = CH(CH₃)₂) and 2d (R = CH₂CH(CH₃)₂), using the polymer substituted with methyl groups ( 1a ). The enantiomeric excess (e.e.) was 10.9% for 2a as a maximum value and decreased in the order of 2a > 2c > 2b = 2d . When the transport of 2a · HPF₆ was carried out using the polymers with 3,4-di-O-methyl ( 1a ), ethyl ( 1b ), allyl ( 1c ), and pentyl ( 1d ) groups, the e.e. was 22.0% for 1d as a maximum value and increased in the order of 1a < 1b < 1c < 1d . The formation of a complex between 1a and 2a · HPF₆ was confirmed by ¹H and ¹³C NMR spectral measurements. © 1995 Wiley-Liss, Inc.