Abstract
Crown ethers (5 a, b) with a pyrrolidine ring and long alkyl chain were synthesized from 4-hydroxyl-L-proline via the five steps shown in Scheme-1. Some physical and aqueous solution properties of (5 a, b) and complexing stability constants (log K1') of these compounds with Na+ and K+ in methanol were examined.
The obtained crown compounds were optically active, [α] 25D : -23.8 and -37.2 (c=1, CH3OH) for (5 a) and (5 b) respectively. Cloud points and the critical micelle concentrations (cmc) of (5 a, b) were lower than those of the reference compounds (6 and 7). The stability constants of (5 a) were less than those for the reference compound (6). The results can be explained on the basis of lipophilicity and steric hindrance of a pyrrolidine unit introduced into the crown ring.
