title: A novel proton-selective sensor based on a sugar with hinge flexibility.
abstract: A hinge sugar, a 2,4-diamino-2,4-dideoxy-beta-D-xylopyranoside derivative, turns its four equatorial substituents into axial orientations through a (4)C(1)-to-(1)C(4) ring flip in response to chelation to a metal ion. This hinge-like motion enables two components attached at the 1- and 3-positions to switch between far and near states. In this study, we examined the effect of N-alkylation on the bendability of the hinge molecule and synthesized a 2,4-dipyrenylmethyl derivative as a proton-selective sensor. (1)H NMR studies showed that N-alkylations of the hinge sugar facilitated (1)C(4) formation in the presence of an acid, probably because the increased basicity of the amino group promoted the intramolecular hydrogen bond between the 2- and 4-amino substituents, whereas chelation to a metal ion was hampered by the increased bulkiness. In accordance with the above results, N,N'-dipyrenylmethyl hinge sugar 3 emitted excimer fluorescence (445 nm) owing to the pyrene stacking as a result of the (1)C(4) formation at lower concentrations of trifuluoroacetic acid (TFA), while no significant changes in fluorescence spectra were observed when metal ions were added. Increase of the monomer fluorescence (375 nm) at higher TFA concentrations was also observed. These observations indicate that 3 could be used as a proton-selective sensor that covers a wide range of proton concentrations through monitoring of the two fluorescence maxima.
authors.affiliation: Department of Life Science, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 J2-10, Nagatsutacho, Midoriku, Yokohama 226-8501, Japan. hyuasa@bio.titech.ac.jp
authors.forename: Hideya
authors.initials: H
authors.lastname: Yuasa
authors.forename: Naohiko
authors.initials: N
authors.lastname: Fujii
authors.forename: Shun
authors.initials: S
authors.lastname: Yamazaki
mesh_terms: D000478:Alkylation; D002241:Carbohydrates / Q000737:chemistry*; D005453:Fluorescence; D009682:Magnetic Resonance Spectroscopy; D011522:Protons; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002241:Carbohydrates; D011522:Protons