Chiral Recognition Ability of Crown Ethers toward Organic Amine Compounds: FAB Mass Spectrometry Coupled with the Enantiomer-Labeles Guest Method.

Sawada, Masami; Hagita, Kouji; Imamura, Hiroyuki; Tabuchi, Hiroyuki; Yodoya, Shinya; Umeda, Masahiro; Takai, Yoshio; Yamada, Hideaki; Yokota, Hiroshi; Hirose, Keiji; Tobe, Yoshito; Tanaka, Toshikazu; Takahashi, Shigetoshi

doi:10.5702/massspec.48.323

Cited by 10 publications

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“…(a) The FAB Mass Spectrometry (MS)/Enantiomer Labeled (El) Guest Method . The chiral discrimination ability of hosts 1 , 2 , and 3 toward various chiral ammonium salts (Chart ) was qualitatively/semiquantitatively evaluated using fast atom bombardment (FAB) mass spectrometry . In this method, the FAB mass spectra of the three component samples in a solution (3-nitrobenzyl alcohol: NBA matrix) containing the hosts (H) and a 1:1 mixture of the ( S ) - enantiomeric guest labeled with deuteriums (G S-dn + ) and the unlabeled ( R ) - enantiomeric guest (G R + ) were measured at room temperature, and the two diastereomeric 1:1 complex ion peaks differing in molecular weight (Δ M = n , n : the number of deuteriums) were compared in intensity in order to estimate the chiral discrimination ability of the host toward the guest.…”

Section: Resultsmentioning

confidence: 99%

New Artificial Host Compounds Containing Galactose End Groups for Binding Chiral Organic Amine Guests: Chiral Discrimination and Their Complex Structures

et al. 2002

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New linear host (1) and cyclic hosts (2 and 3), which have galactopyranose skeletons as chiral origins and oxyethylenes skeletons as binding sites, were designed based on the structural features extracted from the fructo-oligosaccharide derivatives, having a large chiral discrimination ability, and were then synthesized. These hosts showed chiral discrimination toward chiral organic ammonium salts. For example, the chiral discrimination ability (the ratio of association constants: K(R)/K(S)) of host 1, which has the highest value among them, was K(R)/K(S) = 3 for Trp-O-(i)Pr(+) and K(R)/K(S) = 0.7 for 1-(1-naphthyl)ethylammonium (NEA(+)) at 298 K in CHCl(3). It was clarified that host 1 changed the conformation from a linear structure to the pseudo-ring structure by complexation with cations such as alkali metallic ions and chiral organic ammonium ions. The (1)H NMR induced shifts of host 1 by adding the NEA(+) guests showed that the host-guest complex structures are clearly different, depending upon the chirality of the guest; in the complex with (R)-NEA(+), the naphthyl group of the guest is located above the oxyethylene skeleton of the host and in the complex with (S)-NEA(+), and the naphthyl group is located between the edges of the pseudo-ring of the host. The clearly different structure of the complex of host 1 with NEA(+) may be caused by the dynamic molecular recognition, thus the induced-fitting mechanism.

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Section: Resultsmentioning

confidence: 99%

New Artificial Host Compounds Containing Galactose End Groups for Binding Chiral Organic Amine Guests: Chiral Discrimination and Their Complex Structures

et al. 2002

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“…Hosts 1-12 and 14-26 were synthetic compounds, which have already been reported elsewhere. [38][39][40][41][42][43][44][45][46][47][48][49] Commercially available host compounds such as the monensin derivative 13 (Sigma) and 18-crown-6 28 (Aldrich) were used without further purification. Commercial dibenzo-18crown-6 27 (Tokyo Kasei) was recrystallized from chloroform.…”

Section: Methodsmentioning

confidence: 99%

Depression of the Apparent Chiral Recognition Ability Obtained in the Host–Guest Complexation Systems by Electrospray and Nano-Electrospray Ionization Mass Spectrometry

Sawada

Takai

Yamada

et al. 2004

Eur J Mass Spectrom (Chichester)

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Chiral recognition in the host-guest complexation systems of chiral crown ether hosts and amino ester guests was thoroughly examined using the electrospray ionization (ESI) mass spectrometry/enantiomer labeled (EL)-guest method. In this method, the mass spectra of a mixture of three components in a solution, a chiral host (H), an equal amount of an (S)-enantiomer guest labeled with deuterium atoms (G(S-dn)(+)) and an unlabeled (R)-enantiomer guest (G(R)+), were measured and the relative peak intensity value [I(H + G(R))(+) / I(H + G(S-dn))(+) = IRIS] of the host-guest complex ions, observed with an excess guest concentration, was taken to provide the chiral recognition ability of the host. In our earlier report (1996), we demonstrated that the apparent chiral recognition abilities using a mass spectrometer with a homemade ESI interface were depressed by about one tenth compared with the corresponding abilities obtained by fast-atom bombardment (FAB) MS. In the present study, the enantioselective complexation behaviors of various combinations of chiral crown hosts with chiral guests were further investigated in detail mainly using a modern commercial ESI/ion trap (IT) mass spectrometer. Consequently, it was found that the apparent IRIS values from the ESI-MS/EL-guest method changed significantly, depending upon the instrument used, and in particular, upon the ESI interfaces. Moreover, under the specific measuring conditions in ESI-IT-MS, the degrees of depression of the apparent chiral recognition abilities are roughly grouped into three classes, depending upon the number (or probably the type) of the hydrophobic substituents of the hosts. Representing the degrees by the slopes when plotting the apparent IRIS values in ESI-MS versus those in FAB-MS, the slopes for the three classes are (1) 1.0, (2) 0.7 and (3) 0.3; the higher the hydrophobicity of the hosts (and then, the host-guest complex ions), the lower the slope (the apparent enantioselectivity). Strengthening the degree of depression may be caused by an increase in the local concentration of the host close to the surface of the droplets produced during the electrospary ionization process. The chiral recognition ability (K(R )/ K(S)) in an equilibrated solution agrees quite well with the IRIS value in FAB-MS rather than that in ESI-MS.

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“…Although, at present, the origin of this secondary interaction is not clear, an electrostatic interaction between the methoxyl oxygen in the host and the ester carbonyl in the guest is postulated. 59,60…”

Section: Structural Implications Of Host-guest Complex Ionsmentioning

confidence: 99%

Chiral Recognizable Host-Guest Interactions Detected by Fast-Atom Bombardment Mass Spectrometry: Application to the Enantiomeric Excess Determination of Primary Amines

Sawada

Takai

Imamura

et al. 2001

Eur J Mass Spectrom (Chichester)

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The enantiomeric excess (ee) of organic amine compounds has been determined using fast-atom bombardment (FAB) mass spectrometry based on the chiral host-guest complexation systems. The method uses a 1 : 1 mixture of the given chiral crown ether hosts (H RRRR and H SSSS-dn), one of whose enantiomers is isotopically labeled, for the ee-determination of a given amine salt guest (G +). The peak intensity ratio {I[(H RRRR + G) + ] / I[(H SSSS-dn + G) + ] = IRIS} of the two diastereomeric host-guest complex ions clearly changes with the change in the ee of the guest. The intensity excess (I e) of the two complex ion peaks is newly defined as I e = (IRIS-1) / (IRIS + 1). The two sets of mass spectrometrically obtained I e values vs a set of ee values of phenylalanine methyl ester and leucine methyl ester hydrochlorides show excellent linear relationships through the zero point (R 2 = 0.9989 and R 2 = 0.9970, respectively). This indicates the potential utility of the present ee-determination method to within ± 3% ee. Furthermore, based on the solution equilibrium distributions of the complex ions, the linearity is mathematically justified. Therefore, the ee-determination can be simplified as ee (%) = (|I e | / |I e(100) |) × 100: here, I e(100) is the corresponding I e value obtained using an enantiomerically pure (100% ee) guest as a reference. The present chiral dimethoxyphenyl crown ether host pairs employed are effective (IRIS ≥ 1.5) for the ee-determination of most α-amino acid esters, but not effective (IRIS ≈ 1.0) for most simple alkylamines.

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Chiral Recognition Ability of Crown Ethers toward Organic Amine Compounds: FAB Mass Spectrometry Coupled with the Enantiomer-Labeles Guest Method.

Cited by 10 publications

References 0 publications

New Artificial Host Compounds Containing Galactose End Groups for Binding Chiral Organic Amine Guests: Chiral Discrimination and Their Complex Structures

New Artificial Host Compounds Containing Galactose End Groups for Binding Chiral Organic Amine Guests: Chiral Discrimination and Their Complex Structures

Depression of the Apparent Chiral Recognition Ability Obtained in the Host–Guest Complexation Systems by Electrospray and Nano-Electrospray Ionization Mass Spectrometry

Chiral Recognizable Host-Guest Interactions Detected by Fast-Atom Bombardment Mass Spectrometry: Application to the Enantiomeric Excess Determination of Primary Amines

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