Differentiation of diastereomeric cyclic β-amino acids by varying the neutral reagent in ion/molecule reactions studied by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Anna R.M. Hyyryläinen, Jaana M.H. Pakarinen, Pirjo Vainiotalo, Ferenc Fülöp

Research output: Article

6 Citations (Scopus)

Abstract

Stereochemical differentiation of diasteromeric pairs of cis- and trans-2-aminocyclohexane-, -2-amino-4-cyclohexene-, and -2- aminocyclopentanecarboxylic acids was investigated with host-guest complexes where tetraethyl resorcarene was the host molecule. Diastereoselectivity was evaluated by ion/molecule reactions and collision-induced dissociation with electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FTICRMS). The effect of varying the neutral reagent (n-propylamine, i-propylamine, diethylamine, and triethylamine) in ion/molecule reactions was evaluated. Both steric interactions and proton affinity of the neutral reagents influenced the reaction rates. High proton affinity of the neutral reagent apparently had a twofold effect. If the proton affinity of the neutral reagent was too high, the reaction tended to become too exothermic and part of the host-guest complex decomposed instead of transforming to a new host-guest complex, effecting a decrease in the reaction rate. The remaining portion of the host-guest complexes meanwhile reacted very fast with the neutral reagent due to high proton affinity causing an increase in the reaction rate. n-Propylamine and i-propylamine proved to be the best neutral reagents, providing clear diastereoselectivity for β-amino acids in ion/molecule reactions. Interestingly, diastereoselectivity was better for flexible cyclohexane β-amino acids (2 and 3) than for more rigid cyclopentane β-amino acids (6 and 7). The results of ab initio and hybrid density functional theory calculations on the structures of the host-guest complexes of saturated β-amino acids were in good agreement with the experimental results.

Original languageEnglish
Pages (from-to)337-344
Number of pages8
JournalRapid Communications in Mass Spectrometry
Volume22
Issue number3
DOIs
Publication statusPublished - febr. 12 2008

ASJC Scopus subject areas

  • Analytical Chemistry
  • Spectroscopy
  • Organic Chemistry

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