Characteristic conformations and molecular packings in crystal structures of diastereomeric esters prepared from (S)-2-methoxy-2-(1-naphthyl)propanoic acid

Ichikawa, Akio; Ono, Hiroshi; Mikata, Yuji

doi:10.1016/j.tetasy.2008.11.016

Cited by 8 publications

(22 citation statements)

References 25 publications

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“…11 The carboxy groups of (S)-3 formed a chain-like motif called a catemer. 10 X-Ray crystallographic data and NMR spectra of the (R)-MaNP amide 3,11 suggested that the methine group of the amine moiety and the carbonyl group were syn, while the carbonyl and the methoxy groups were anti (Fig. 9 The crystalline conformation of the (S)-MaNP ester was similar to those of acids (S)-1 and (S)-3 as follows (Fig.…”

Section: Introductionmentioning

confidence: 93%

“…1,3,[9][10][11] These properties make acids 1-3 useful as stereochemical internal standards for X-ray crystallography, which is considered the most reliable method for elucidating stereochemistry. 1,3,[9][10][11] These properties make acids 1-3 useful as stereochemical internal standards for X-ray crystallography, which is considered the most reliable method for elucidating stereochemistry.…”

Section: Introductionmentioning

confidence: 99%

“…In crystalline (S)-3, the hydroxy and carbonyl groups were syn, as were the carbonyl and methoxy groups. 3,[9][10][11] The methine group of the alcohol moiety and the carbonyl group were syn. 11 The carboxy groups of (S)-3 formed a chain-like motif called a catemer.…”

Section: Introductionmentioning

confidence: 99%

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Crystal structures and chiral recognition of the diastereomeric salts prepared from 2-methoxy-2-(1-naphthyl)propanoic acid

et al. 2011

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This paper is the first to report the structures of crystalline diastereomeric salts 8 and 9 prepared from (R)-2-methoxy-2-(1-naphthyl)propanoic acid [(R)-MaNP acid, (R)-1] and (S)-1 with (R)-1phenylethylamine [(R)-PEA, (R)-7], respectively. These crystal structures helped elucidate a novel chiral recognition mechanism characteristic of MaNP salts. The less-soluble diastereomeric salt 8 prepared from (R)-1 and (R)-7 formed an ammonium-carboxylate ion pair by means of a methoxy-assisted salt bridge and an aromatic CH/p interaction. The more-soluble diastereomeric salt 9 prepared from (S)-1 and (R)-7 formed an ion pair by a methoxy-assisted salt bridge in which the 1-naphthyl and phenyl groups did not overlap. Instead, salt 9 formed a close ion pair by means of a salt bridge, a CH/O hydrogen bond, and a p/p interaction. These crystal structures suggest that the molecular length from the MaNP plane containing the carboxy and methoxy groups is critical to the crystallisation of diastereomeric salts. The crystal packing in both salts was investigated with regard to the weak interactions (i.e., salt bridges, NH/O and CH/O hydrogen bonds, and aromatic CH/p, CH/p, and p/p interactions). Finally, diastereomeric amides 11 and 12 were prepared from (S)-2-methoxy-2-(2-naphthyl)propanoic acid [(S)-MbNP acid, (S)-2] and (R)-2 with (S)-1-(1-naphthyl)ethylamine [(S)-10]. The solution-phase structures of the MbNP amides, and their separation, was investigated by NMR spectroscopy and high-performance liquid chromatography (HPLC). The less-stereochemically demanding and longer 2-naphthyl group made the MbNP amide more flexible and less polar than the MaNP amide. Acid 2 was more efficient than acid 1 in separating amides 11 and 12.

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Section: Introductionmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Crystal structures and chiral recognition of the diastereomeric salts prepared from 2-methoxy-2-(1-naphthyl)propanoic acid

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“…We reported that the agreement of the molecular lengths of acid/alcohol moieties is important for the crystallization of MαNP esters [16].…”

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confidence: 95%

“…We studied on three chiral resolving agents [i.e., MαNP acid (2), MβNP acid (3), and M9PP acid (4)] based on their enantioresolution of chiral alcohols and elucidation of absolute configurations [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24]. The resolving ability of 2 is superior to that of 1 in normal phase HPLC.…”

Section: Introductionmentioning

confidence: 99%

Characteristic Conformation of Mosher’s Amide Elucidated Using the Cambridge Structural Database

2015

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Abstract:Conformations of the crystalline 3,3,3-trifluoro-2-methoxy-2-phenylpropanamide derivatives (MTPA amides) deposited in the Cambridge Structural Database (CSD) were examined statistically as Racid-enantiomers. The majority of dihedral angles (48/58, ca. 83%) of the amide carbonyl groups and the trifluoromethyl groups ranged from -30° to 0° with an average angle θ 1 of −13°. The other conformational properties were also clarified: (1) one of the fluorine atoms was antiperiplanar (ap) to the amide carbonyl group, forming a staggered conformation; (2) the MTPA amides prepared from primary amines showed a Z form in amide moieties; (3) in the case of the MTPA amide prepared from a primary amine possessing secondary alkyl groups (i.e., Mosher-type MTPA amide), the dihedral angles between the methine groups and the carbonyl groups were syn and indicative of a moderate conformational flexibility; (4) the phenyl plane was inclined from the O-Cchiral bond of the methoxy moiety with an average dihedral angle θ 2 of +21°; (5) the methyl group of the methoxy moiety was ap to the ipso-carbon atom of the phenyl group.

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Naphthyl Groups in Chiral Recognition: Structures of Salts and Esters of 2‐Methoxy‐2‐naphthylpropanoic Acids

Ichikawa

Ono

Mikata

2012

Chemistry An Asian Journal

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The crystal structures of salt 8, which was prepared from (R)-2-methoxy-2-(2-naphthyl)propanoic acid ((R)-MβNP acid, (R)-2) and (R)-1-phenylethylamine ((R)-PEA, (R)-6), and salt 9, which was prepared from (R)-2-methoxy-2-(1-naphthyl)propanoic acid ((R)-MαNP acid, (R)-1) and (R)-1-(p-tolyl)ethylamine ((R)-TEA, (R)-7), were determined by X-ray crystallography. The MβNP and MαNP anions formed ion-pairs with the PEA and TEA cations, respectively, through a methoxy-group-assisted salt bridge and aromatic CH⋅⋅⋅π interactions. The networks of salt bridges formed 2(1) columns in both salts. Finally, (S)-(2E,6E)-(1-(2) H(1) )farnesol ((S)-13) was prepared from the reaction of (2E,6E)-farnesal (11) with deuterated (R)-BINAL-H (i.e., (R)-BINAL-D). The enantiomeric excess of compound (S)-13 was determined by NMR analysis of (S)-MαNP ester 14. The solution-state structures of MαNP esters that were prepared from primary alcohols were also elucidated.

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Characteristic conformations and molecular packings in crystal structures of diastereomeric esters prepared from (S)-2-methoxy-2-(1-naphthyl)propanoic acid

Cited by 8 publications

References 25 publications

Crystal structures and chiral recognition of the diastereomeric salts prepared from 2-methoxy-2-(1-naphthyl)propanoic acid

Crystal structures and chiral recognition of the diastereomeric salts prepared from 2-methoxy-2-(1-naphthyl)propanoic acid

Characteristic Conformation of Mosher’s Amide Elucidated Using the Cambridge Structural Database

Naphthyl Groups in Chiral Recognition: Structures of Salts and Esters of 2‐Methoxy‐2‐naphthylpropanoic Acids

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