Structural Scaffold of 18-Crown-6 Tetracarboxylic Acid for Optical Resolution of Chiral Amino Acid: X-Ray Crystal Analyses of Complexes of D- and L-Isomers of Serine and Glutamic Acid

Nagata, Hiroomi; Nishi, Hiroyuki; Kamigauchi, Miyoko; Ishida, Toshimasa

doi:10.1248/cpb.54.452

Cited by 14 publications

(17 citation statements)

References 25 publications

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“…2, (1) and (2)]. This conformation has also been observed in complexes of (1)-18C6H x with various optically active amino acids 19,20 and R-1-(1-naphthyl)-ethylamine. 26 Previously, we reported that the C 1 conformation of (1)-18C6H x could be further classified into three types, i.e.…”

Section: Conformation Of Crown Ether Ringsupporting

confidence: 57%

“…Similar conformation has been observed in (1) Table 2). The short contacts 29 were observed for the Ca-HÁ Á ÁO, as shown in Figure 2 19,20 and are considered to be a major force for chiral separation of racemic amino acids.…”

Section: Conformation Of Crown Ether Ringmentioning

confidence: 99%

“…[7][8][9][10] In addition, (1)-18C6H 4 is also used as a chiral selector for amine compounds in capillary electrophoresis (CE) [11][12][13][14][15] or nuclear magnetic resonance (NMR). [16][17][18] To clarify the structural scaffold of (1)-18C6H 4 necessary for D/L-separation of racemic amino acids, we recently determined the crystal structures of (1)-18C6H 4 complexed with D-and L-isomers of tyrosine (Tyr), isoleucine (Ile), methionine (Met), phenylglycine (PheG), serine (Ser), and glutamic acid (Glu) by X-ray diffraction method, 19,20 and showed that all four carboxyl groups of (1)-18C6H 4 are deprotonatable and take the formula (1)-18C6H x , x 5 0-4, charge 5 24-0, depending on the interaction with the guest molecule. Consequently, we proposed that the structural scaffold of (1)-18C6H x necessary for chiral separation has mainly an asymmetrical bowl-like shape and is dependent on specific interactions between the amino and CaÀ ÀH groups of the optically active amino acid and the polar oxygen atoms of (1)-18C6H x .…”

Section: Introductionmentioning

confidence: 99%

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Guest‐dependent conformation of 18‐crown‐6 tetracarboxylic acid: Relation to chiral separation of racemic amino acids

Nagata¹,

Nishi²,

Kamigauchi

et al. 2008

Chirality

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(+)-18-crown-6 tetracarboxylic acid (18C6H(4)) has been used as a chiral selector for various amines and amino acids. To further clarify the structural scaffold of 18C6H(4) for chiral separation, single crystal X-ray analysis of its glycine(+) (1), H3O+ (2), H5O2+ (3), NH4+ (4), and 2CH3NH3+ (5) complexes was performed and the guest-dependent conformation of 18C6H(4) was investigated. The crown ether ring of 18C6H4 in 3, 4, and 5 took a symmetrical C2 or C2-like conformation, whereas that in 1 and 2 took an asymmetric C1 conformation, which is commonly observed in complexes with various optically active amino acids. The overall survey of the present and related complexes suggests that the molecular conformation of 18C6H4 is freely changeable within an allowable range, depending on the molecular shape and interaction mode with the cationic guest. On the basis of the present results, we propose the allowable conformational variation of 18C6H4 and a possible transition pathway from its primary conformation to the conformation suitable for chiral separation of racemic amines and amino acids.

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Section: Conformation Of Crown Ether Ringsupporting

confidence: 57%

Section: Conformation Of Crown Ether Ringmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Guest‐dependent conformation of 18‐crown‐6 tetracarboxylic acid: Relation to chiral separation of racemic amino acids

Nagata¹,

Nishi²,

Kamigauchi

et al. 2008

Chirality

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“…Previous studies with x-ray crystallography and nuclear magnetic resonance spectroscopy have demonstrated the affinity of 18c6H 4 for protonated amines, amino acids, amino alcohols and further compounds with free amino functionality. [8][9][10][11][12][13][14][15][16] Those studies have provided evidence for the relevance of the barrel-like and bowl-like structures adopted by 18c6H 4 . Such structures are sustained by intramolecular H-bonding involving the carboxyl groups and by intermolecular interactions of the cationic guest with the ether and carboxyl oxygen atoms.…”

Section: Introductionmentioning

confidence: 85%

Multipodal coordination of a tetracarboxylic crown ether with ${\rm NH}_4^+$ NH 4+: A vibrational spectroscopy and computational study

Hurtado

Gámez

Hamad

et al. 2012

The Journal of Chemical Physics

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The elucidation of the structural requirements for molecular recognition by the crown ether (18-crown-6)-2,3,11,12-tetracarboxylic acid (18c6H(4)) and its cationic complexes constitutes a topic of current fundamental and practical interest in catalysis and analytical sciences. The flexibility of the central ether ring and its four carboxyl side arms poses important challenges to experimental and theoretical approaches. In this study, infrared action vibrational spectroscopy and quantum mechanical computations are employed to characterize the conformational structure of the isolated gas phase complex formed by the 18c6H(4) host with NH(4)(+) as guest. The results show that the most stable gas-phase structure is a barrel-like conformation sustained by tetrapodal H-bonding of the ammonia cation with two C=O side groups and with four oxygen atoms of the ether ring in a bifurcated arrangement. Interestingly, a similar structure had been proposed in previous crystallographic studies. The experiment also provides evidence for a significant contribution of a higher energy bowl-like conformer with features resembling those adopted by 18c6H(4) in the analogous complexes with secondary amines. Such a conformation displays H-bonding between confronted side carboxyl groups and tetrapodal binding of the NH(4)(+) with the ether ring and with one C=O group. Structures involving even more extensive intramolecular H-bonding in the 18c6H(4) substrate are found to lie higher in energy and are ruled out by the experiment.

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“…Six multicomponent crystals of serine with organic counterparts containing carboxylic acid groups are known, namely l-serinium (+)-18-crown-6-tetracarboxylic acid perchlorate monohydrate and d-serinium (+)-tricarboxy-18-crown-6-carboxylate hexahydrate (Nagata et al, 2006), bis(dl-serinium) oxalate dihydrate (Alagar et al, 2002a), bis(l-serinium) oxalate dihydrate (forms I and II) (Braga et al, 2013), and a cocrystal of l-serine with pyridine-2,4-dicarboxylic acid (Liang, 2008). No anhydrous serinium salts or cocrystals of l and dl counterparts with the same chemical composition have been reported thus far.…”

Section: Commentmentioning

confidence: 99%

Semi-maleate salts ofL- andDL-serinium: the first example of chiral and racemic serinium salts with the same composition and stoichiometry

2013

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L-serinium semi-maleate, (I), and DL-serinium semi-maleate, (II), both C3H8NO3(+)·C4H3O4(-), provide the first example of chiral and racemic anhydrous serine salts with the same organic anion. A comparison of their crystal structures with each other, with the structures of the pure components (L-serine polymorphs, DL-serine and maleic acid) and with other amino acid maleates is important for understanding the formation of the crystal structures, their response to variations in temperature and pressure, and structure-property relationships. As in other known crystal structures of amino acid maleates, there are no direct links between the semi-maleate anions in the two new structures. The serinium cations have different conformations in (I) and (II). In (I), they are linked into infinite chains via hydrogen bonds between carboxylic acid and hydroxy groups. In (II), there are no such chains formed by the serinium cations. In both (I) and (II), there are C2(2)(12) chains consisting of alternating semi-maleate anions and serinium cations. Two types of such chains are present in (I) and (II), termed C2(2)(12) and C2(2)(12)'. In (I), these chains, lying in the same plane, are further linked to each other via hydrogen bonds, whereas in (II) they are not.

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Structural Scaffold of 18-Crown-6 Tetracarboxylic Acid for Optical Resolution of Chiral Amino Acid: X-Ray Crystal Analyses of Complexes of D- and L-Isomers of Serine and Glutamic Acid

Cited by 14 publications

References 25 publications

Guest‐dependent conformation of 18‐crown‐6 tetracarboxylic acid: Relation to chiral separation of racemic amino acids

Guest‐dependent conformation of 18‐crown‐6 tetracarboxylic acid: Relation to chiral separation of racemic amino acids

Multipodal coordination of a tetracarboxylic crown ether with ${\rm NH}_4^+$ NH 4+: A vibrational spectroscopy and computational study

Semi-maleate salts ofL- andDL-serinium: the first example of chiral and racemic serinium salts with the same composition and stoichiometry

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