The gas-phase chemistry of deprotonated benzyl N-phenylcarbamates was investigated by electrospray ionization tandem mass spectrometry. Characteristic losses of a substituted phenylcarbinol and a benzaldehyde from the precursor ion were proposed to be derived from an ion-neutral complex (INC)-mediated competitive proton and hydride transfer reactions. The intermediacy of the INC consisting of a substituted benzyloxy anion and a phenyl isocyanate was supported by both ortho-site-blocking experiments and density functional theory calculations. Within the INC, the benzyloxy anion played the role of either a proton abstractor or a hydride donor toward its neutral counterpart. Relative abundances of the product ions were influenced by the nature of the substituents. Electron-withdrawing groups at the N-phenyl ring favored the hydrogen transfer process (including proton and hydride transfer), whereas electron-donating groups favored direct decomposition to generate the benzyloxy anion (or substituted benzyloxy anion). By contrast, electron-withdrawing and electron-donating substitutions at the O-benzyl ring exhibited opposite effects.

The noncovalent complex interactions between cyclofructans, a new class of cyclic oligosaccharide hosts, and various amino acids have been characterized by means of electrospray ionization mass spectrometry and nuclear magnetic resonance. The 1 : 1 stoichiometry of cyclofructans and amino acid complexes was confirmed by their mass-to-charge ratio in positive mode. Cyclofructans (CFs)-amino acid complexes and cyclodextrin-amino acid complexes exhibited distinctive different fragment behaviors in collision-induced dissociation experiments. Coupled with the results of (1) H NMR and nuclear overhauser effect spectroscopy, cyclofructan-amino acid complexes were deduced to be rim complexes via formation hydrogen bondin and ion-dipole forces. The interaction pattern could be controlled by changing the pH condition. In neutral solution, amino acids are located on the positive side of CFs, although moved to the negative side pocket constructed by 3-OH oxygen of furanose ring and the crown ether oxygen in acid condition. In addition, theory calculation for geometry optimization of Trp and CFs was performed, which was in good agreement with the experimental results.