First successful molecular design of an artificial Lewis oligosaccharide binding system utilizing positive homotropic allosterism

We have designed phenylboronic acid group appended Ce(IV) bis(porphyrinate) double decker 1 and meso - meso linked porphyrin 2, useful for the allosteric binding of biologically important saccharides, Lewis oligosaccharides. Compound 1 binds Lewis oligosaccharides in aqueous media because of the boronic acid-diol interaction, but the complexation event can occur only above the critical concentrations because of the sigmoidal [oligosaccharide] versus [complex] isotherm. Compound 1 has a sufficiently high affinity with Lewis oligosaccharides (K = 10⁵-10⁶ M^-2) with Hill coefficients n of 1.8-2.0, and Lewis^X series and Lewis^a series give opposite, symmetrical CD spectra. This is the first example of efficient binding of Lewis oligosaccharides to the artificial receptor, which has become possible by positive homotropic allosterism.