title: Catalytic specificity exhibited by p-sulfonatocalix[n]arenes in the methanolysis of N-acetyl-l-amino acids.
abstract: Specific acid catalysis of p-sulfonatocalix[n]arenes (n = 4, Calix-S4; n = 6, Calix-S6; n = 8, Calix-S8) was observed in the alcoholysis of N-acetyl-l-amino acids in methanol. The methanolysis rates of basic amino acid substrates (His, Lys, and Arg) were markedly enhanced in the presence of Calix-Sn, as compared with rates observed with p-hydroxybenzenesulfonic acid (pHBS), which is a noncyclic analogue of Calix-Sn. This catalytic effect of Calix-Sn was not observed for the methanolysis of Phe, Tyr, and Trp substrates. On the other hand, (1)H NMR experiments following the effect of Calix-Sn on N-acetyl-l-amino acid substrates in CD(3)OD showed that the spectrum of a mixture of the His substrate with Calix-Sn was significantly different from the combined spectra of the respective compounds. These changes in spectra support the formation of an inclusion complex of Calix-Sn with basic amino acids. Furthermore, it was obvious that methanolysis of the His substrate catalyzed by Calix-S4 and Calix-S6 obeyed Michaelis-Menten kinetics. These results indicate that the catalytic activity of Calix-Sn originates from its forming a complex with specific substrates (basic amino acids), similar to enzymatic reactions.
authors.affiliation: Division of Applied Chemistry, Graduate School of Sojo University, 4-22-1 Ikeda, Kumamoto 860-0082, Japan.
authors.forename: Koichi
authors.initials: K
authors.lastname: Goto
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Yano
authors.forename: Eiji
authors.initials: E
authors.lastname: Okada
authors.forename: Chin-Wen
authors.initials: CW
authors.lastname: Liu
authors.forename: Kiyoto
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Ueoka
mesh_terms: D000596:Amino Acids / Q000737:chemistry*; D047250:Calixarenes; D002384:Catalysis; D007700:Kinetics; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D010636:Phenols / Q000737:chemistry*; D013237:Stereoisomerism; D013379:Substrate Specificity; D013451:Sulfonic Acids / Q000737:chemistry; D013997:Time Factors
chemical_list: D000596:Amino Acids; D046911:Macromolecular Substances; D010636:Phenols; D013451:Sulfonic Acids; D047250:Calixarenes