Synthesis of functionalized porphyrins as oxygen ligand receptors.
Oxophilic synthetic receptors were designed and synthesized using a porphyrin scaffold, with the aim of constructing a preorganized complementary binding site for phenols and carbohydrates. We pursued three strategies for phenol recognition: (1) Lewis acid/Lewis base combinations serving as a hydrogen bond donor and acceptor for the OH group, (2) Lewis base/pi-pi stacking, targeting both the OH group and the aromatic moiety of phenols, and (3) exchange of the axial hydroxyl ligand on a trivalent and oxophilic metal center of aluminum porphyrin. For the recognition of acidic phenols, the most promising recognition motif was Lewis base/pi-pi stacking, which can bind to phenols with a hydrogen bond and pi-pi stacking interactions. [5-(8-Quinolyl)-10,15,20-triphenylporphyrinato]zinc binds to p-nitrophenol with a binding constant of 540 M(-)(1) in CHCl(3) at 25 degrees C. For carbohydrate recognition, we designed the metalloporphyrin receptor having 8-quinolyl groups and o-carbomethoxymethoxyphenyl groups, where these Lewis basic parts serve as the cooperative hydrogen bonding sites for the hydroxyl groups of glucoside. The receptor binds to beta-octyl glucoside with a binding constant of 7.35 x 10(4) M(-)(1) in CHCl(3) at 15 degrees C, demonstrating importance of formation of a highly ordered hydrogen bonding network between the receptor and the guest. These binding features have significant implications for the rational design of oxophilic artificial receptors.
Wada
Kenji
K
Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
Mizutani
Tadashi
T
Kitagawa
Susumu
S
D001665:Binding Sites; D002241:Carbohydrates / Q000737:chemistry*; D015195:Drug Design; D009682:Magnetic Resonance Spectroscopy; D008665:Metalloporphyrins / Q000138:chemical synthesis*; D008958:Models, Molecular; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry*; D010636:Phenols / Q000737:chemistry*; D011955:Receptors, Drug / Q000737:chemistry*; D015032:Zinc / Q000737:chemistry*
D002241:Carbohydrates; D008665:Metalloporphyrins; D010636:Phenols; D011955:Receptors, Drug; D015032:Zinc; D010100:Oxygen