1 JOURNAL OF INCLUSION PHENOMENA AND MACROCYCLIC CHEMISTRY (ISSN: 1388-3127) (eISSN: 1573-1111) 2014: pp. 1-9. (2014) DOI: 10.1007/s10847-014-0384-8 Synthesis and recognition properties of α-D-glucose-based fluorescent crown ethers incorporating an acridine unit Zsolt Rapi, 1 Péter Bakó, 1 * György Keglevich, 1 Péter Baranyai, 2 Miklós Kubinyi, 2,3 Olívia Varga 2 1 Department of Organic Chemistry and Technology, Budapest University of Technology and Economics, PO Box 91, 1521 Budapest, Hungary, E-mail: pbako@mail.bme.hu 2 Institute of Molecular Pharmacology, Research Centre for Natural Sciences, Hungarian Academy of Sciences, PO Box 17, H-1525 Budapest, Hungary 3 Department of Physical Chemistry and Materials Science, Budapest University of Technology and Economics, PO Box 91, 1521 Budapest, Hungary Abstract: Two new chiral glucopyranoside-based crown ethers incorporating acridine fluorescent signalling units, 15-membered ligand 1 and 21-membered ligand 2 were synthesized. Their complexation properties toward alkali and alkali earth metal ions, and their enantioselectivity towards chiral ammonium salts were studied by absorption and fluorescence spectroscopic experiments. Macrocycle 1 formed 1:1 complexes with all the metal ions selected and the stability constants were low (lg K < 2.3). The cavity-size of 2 allowed only the complexaton of organic ammonium ions. Crown 2 showed chiral discrimination in case of all the four ammonium salts used as model guest compounds; the highest enantioselectivity (K(R)/K(S)  3) was observed for the enantiomers of phenylethyl ammonium (PEA) perchlorate. Ligand 2 forms much more stable complexes with metal ions; the highest stability constant was obtained for the Ca 2+ complex (lg K = 6.15). The coordination of metal ions by ligand 2 was accompanied by marked fluorescence enhancement, whereas the binding of ammonium ions by the same species resulted in significant fluorescence quenching. Keywords: Chiral crown ethers, carbohydrate-based crown ethers, fluorescence, complexation, enantiomeric recognition, photoinduced electron transfer (PET)