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.