Efficient complexation of quaternary ammonium compounds by a new water-soluble macrobicyclic receptor molecule

Abstract

The hexacarboxylic macrobicycle 1 is a readily accessible water-soluble receptor molecule which binds strongly quaternary ammonium cations.

Selective Complexation of N‐Alkylpyridinium Salts: Binding of NAD+ in Water

“…Complex stabilities: In contrast to complexes of dimethylene-bridged clips of type 1 in aprotic organic solvents, [58] clip 1 a forms highly stable complexes with the N-alkylpyridinium and -imidazolinium salts 15-21, NAD + (22), NADP (23), 2'-desoxyadenosine (24), AMP (25), and NMN (26) in protic solvents such as methanol and water (Table 3) ). [44] This result and the finding that the complexes of 1 a formed in water (K a = 4800-83000 m…”

“…Although this allows the NAD-1 structure to be discarded, no final and safe conclusion about how the adenine or nicotinamide moiety of NAD + is bound to the clip can be drawn at this stage of our quantum chemical studies due to the multitude of possible structural arrangements. Here, further investigations are planned, in particular with the smaller ribose-substituted systems such as 2'-desoxyadenosine (24), AMP (25), and NMN (26).…”

“…Even nucleosides such as adenosine are likewise drawn into the clips cavity. Complex formation and structures were examined by one-and twodimensional NMR spectroscopy, Job plot analyses, and isothermal titration microcalorimetric (ITC) measurements, as well as quantum chemical calculations of 1 interaction to bind organic cations such as quaternary ammonium ions, [24][25][26][27][28][29][30] guanidinium ions, [31,32] and N-alkylpyridinium ions. [33][34][35][36] However, these macrocyclic structures have a different selectivity towards their substrates; most of them prefer spherical over flat guests.…”

“…We checked this interesting hypothesis with the naturally occurring nucleosides 2'-desoxyadenosine (24) and adenosine monophosphate AMP (25). A remarkably high binding constant of K a = 5300 AE 300 m À1 was determined for complex formation between the neutral guest molecule 24 and clip 1 a from the 1 H NMR titration curve.…”

Application of Thiacrown Ethers as Ligands for Lead-Selective Electrodes

“…After the standard workup the residue was chromatographed over silica gel with dichloromethane as the eluent. The fractions containing ligand 3 were evaporated, yielding a white solid which was crystallized from acetone, affording 0.87 g (18%) of the pure ligand, mp 111˚C, EIMS: m/z 640; 1 10,15,20,29,7,23,). An excess of potassium carbonate (10.35 g, 75 mmol) was added to a solution of 4,4′-thiobisbenzenethiol (6.26 g, 25 mmol) and triethylene glycol monochloride (8.43 g, 50 mmol) in acetonitrile (200 ml), and the resulting mixture was refluxed for 4 d under a nitrogen blanket.…”