Complexation studies of nucleotides by tetrandrine derivatives bearing anthraquinone and acridine groups

Water soluble dicationic cyclophane-type macrocycles bearing two anthraquinone (1) or two acridine groups (2) have been prepared by chemical modification of S,S-(+)-tetrandrine. Complexation of nucleotide anions (mono- di- and triphosphates) and D/L phenylalanine by tetrandrine derivatives has been studied by UV-Visible and fluorescence titrations in water. Association of nucleotides to semi-synthetic hosts 1 and 2 increases with increasing guest charge in the series AMP2- ADP3- ATP4-. It was demonstrated for the 1- ATP and ADP complexes that association strength is increased in the absence of salt (NaCl). Besides, receptor 1 shows a slight preference for the complexation of UMP over nucleotides containing A (adenine), G (guanine), C (cytosine) or T (thymine) as bases. The major forces stabilizing the complexes result from ion pairing between the charged groups of host and guest and from stacking or hydrophobic interactions. Receptor 1 displayed chiral recognition towards D/L phenylalanine.