Enantioselective Complexation of Chiral Dicarboxylic Acids in Clefts of Functionalized 9,9′‐Spirobifluorenes

The 9,9′-spirobifluorene receptors (R)- and (S)-1 with amidopyridine groups in the 2 and 2′ positions complex chiral dicarboxylic acids enantioselectively in chloroform by hydrogen bonding. Interestingly, the N-protected acidic amino acids, L-aspartic and L-glutamic acid, prefer binding to different hosts. In contrast, 1,1′-binaphthyl receptors with similar functionality in the major groove show hardly any enantioselectivity in the complexation of chiral dicarboxylic acids.