Michał J. Chmielewski

Synthesis, structure, and complexing properties of macrocyclic receptors for anions*

Understanding of structure-affinity relationships is crucial for rational receptor design, however, such studies for anion receptors are still limited. Therefore, we investigated this issue in the case of amide-based macrocyclic receptors derived from aromatic diacids (i.e., isophthalic and dipicolinic). Using these model compounds, we examined the macrocyclic effect, the influence of intramolecular hydrogen bonds, and the correlation between the ring size and anion affinity. We found that in contrast to what was known for acyclic diamides, macrocyclic isophthalamide receptors bind anions more weakly than their dipicolinic analogs. Comprehensive structural studies revealed that such behavior is due to intramolecular hydrogen bonds present in isophthalamide receptors. Furthermore, we demonstrated how this obstacle can be overcome by the preparation of a hybrid macrocycle based on both building blocks.

The synthesis of optically pure β-lactams derived from sugars. High-pressure [2+2] cycloaddition of toluene-4-sulphonyl isocyanate to glycals.

Abstract [2+2] Cycloaddition of toluene-4-sulphonyl isocyanate to glycals 1 - 4 at room temperature under 10 kbar pressure gave respective β-lactams 5 - 8 in good yields. The reaction proceeds regio- and stereospecifically to afford the four-membered ring in position trans to the acetoxy group at C-3 of the glycal moiety.

Benzopyrrole derivatives as effective anion receptors in highly competitive solvents

Neutral anion receptors working in highly demanding solvents are new materials being sought. Benzopyrroles are more acidic than amides and pyrrole itself, and are promising building blocks in the design of host compounds. A whole series of receptors based upon benzopyrroles were synthesized and evaluated. They include carbazole, dipyrrolonaph-thalene, and 7-aminoindole-based hosts. Most of them demonstrate moderate binding affinities in dimethyl sulfoxide (DMSO) and have good selectivity toward tetrahedral oxyanions. Recently, a group of receptors utilizing 7-aminoindole and urea moieties proved to work in a very competitive solvent—methanol.