Carbohydrate Recognition through H-Bonding and CH-π Interactions by Porphyrin-Based Receptors

Porphyrin-based synthetic receptors containing urea, carbamate, or amide groups were designed and synthesized for carbohydrate recognition The receptors have equatorially and convergently directed hydrogen-bonding sites into which the urea, carbamate, or amide groups were introduced above the porphyrin plane The receptors exhibited remarkable affinities to pyranoside/furanoside derivatives in organic media, demonstrating not only the importance of multiple hydrogen-bonding interactions but also CH-pi interactions in carbohydrate recognition Among the three hydrogen-bonding groups, urea NHs were used as the strongest H-bonding donors for sugar hydroxyl oxygens, and the porphyrin plane was used for mimicking CH-pi interactions with sugar CHs, which are found in sugar-binding proteins The binding interactions between the artificial receptors and carbohydrates were elucidated by various spectroscopic analyses such as UV-vis titration, H-1 NMR titration, CD measurement, and computer-assisted modeling