Novel C2-symmetric macrocycles bearing diamide-diester groups:: Synthesis and enantiomeric recognition for primary alkyl ammonium salts

We synthesized a series of novel macrocycles with diamide-diester groups (S,S)-1, (S,S)-2, (S,S)-3, and (R,R)-1, derived from dimethyloxalate and amino alcohols by high dilution technique, and evaluated enantiomeric recognition properties of these macrocycles toward primary alkyl ammonium salts by H-1 NMR titration. Taking into account the host employed, important differences were observed in the K-a values of (R)-Am and (S)-Am for (S,S)-1 and (R,R)-1 hosts, K-S/K-R = 5.55 and K-R/K-S = 3.65, Delta Delta G(o) = 0.43 and -0.32 kJ mol(-1), respectively. There seems a general tendency for the host to include the guests with the same absolute configuration.