Chiral Recognition in Host-Guest Complexation Determined by the Enantiomer-Labeled Guest Method Using Fast Atom Bombardment Mass Spectrometry

Abstract

Chiral recognition in host-guest complexations between crown ether hosts (H) and amino acid ester ammonium ion guests (G+) has been evaluated by fast atom bombardment @AB) mass spectrometry (m-nitrobenzyl alcohol matrix). The method uses a 1/1 mixed (for example, GR' and Cis-&+) solution of the guest whose enantiomer is isotopically (deuterium) labeled. Chiral recognition of a given host is simply measured with a given guest from the peak intensity ratio of the two diastereomeric host-guest complex ions as I [(H f GR)+]/I[(H -I-Gs-d,)'] 3 IR/&-d,.Both the degree and the direction of chiral recognition are characterized by the I,&-d, values in the range from 0.5 to 5.4 (IR/&-d3) for the present host-guest combination systems studied. b o n g several synthetic chird crown ethers and related natural host compounds, it has been found that host 5 possesses remarkably large guest dependence upon the chiral recognition properties: (1) toward primary amino acid ester guests 14-21, a high degree of (R)-enantiomer preference (I,& = 3.2-5.4), (2) toward phenylglycine ester guest 22, almost no enantiomer recognition (IR/ZS = l.l), and (3) toward secondary amino acid ester guest 24, a weak (S)-enantiomer preference (IR/ZS = 0.7). It is also shown that the IR/Z~ values measured with the present concentrations are reasonably correlated with the relative thermodynamic stabilities in the corresponding host-guest equilibria in solution (IR/IS I KR/KS) for three typical host-guest combination systems selected (1-22,4-16, and 5-16). Accordingly, the present FABMS/ EL (enantiomer-labeled guest) method can be proposed as a new and practically useful technique for determining chiral recognition properties in the highly structured chiral host-chiral guest complexations.

Naked-Eye Detectable Chiral Recognition Using a Chromogenic Receptor

“…The apparent association constant (K) calculated was 66 ±8.8 dm 3 mol -1 . Quantitative evidence for complexation was given by FAB mass spectrometry 17 (m-nitorobenzyl alcohol matrix), where Xe was used as an atom beam accelerated to 3.0 keV. The detection of the peak m/z 1181 indicated the formation of a 1:1 complex between 1a and (R)-2.…”

Study of formation and fragmentation of ionic complexes of polydentate ligands with Al(III) and glycerol by fast atom bombardment mass spectrometry. Part 1: Polydentate ligands

“…The dissociation of (M + Mass spectra of glycols obtained from AlC1,-glycerol-TFA The FAB mass spectra of mono-(8), di-(9), tri-(lo), tetra-( l l ) , penta-(12), and hexaethylene glycols (13) were run in the A1Cl3 -glycerol -water and TFA matrix mixture. Relative abundances of ions obtained from these compounds are listed in Table 3 Formation of a cyclic (M + A1 -2H)' ion depends on the number of ethylene oxide (C2H40) units and is observed from triethylene glycol to pentaethylene glycol as the base peak.…”

The Asymmetry is Derived from Mechanical Interlocking of Achiral Axle and Achiral Ring Components –Syntheses and Properties of Optically Pure [2]Rotaxanes–

“…Many crops from this field of chemistry were industrialized such as ion sensors, ion selective membranes, and electrodes [4][5][6][7][8][9], which were contributed by ion recognition initiated by C. J. Pedersen and chiral selectors for chromatography [10][11][12][13][14][15] initiated by the contribution of D. J. Cram's chirality recognition technology [16,17]. Research topics such as chiral shift reagents for the determination of enantiomeric excess of chiral substance [18], besides the reagents for the determination of absolute configuration [19,20], chiral indicators [19,[21][22][23][24], and rapid chirality detection method using chiral hosts by means of mass spectrometry [25,26], as well as other well established methods [27][28][29] have long fascinated many researchers.…”