Cholic acid-based fluorescent probes for enantioselective recognition of trifunctional amino acids

The ditopic fluorescent photoinduced electron transfer (PET) amino acid sensory probes 1a and 1c were designed and synthesized from cholic acid. To confer the probes with specific binding ability, an amidothiourea moiety and a cyclic diamino-chiral receptive site were introduced on the C17 side chain and the C7 and C12 hydroxyl pendants, respectively. In acetonitrile, the probes demonstrated differential binding toward trifunctional amino acids like serine, lysine, threonine and tyrosine against other simple amino acids. Enantioselectivities (K_D/K_L) of up to 8.9 and sensitivities in the micromolar range with the probes were observed for trifunctional amino acids.