title: Characteristic conformation of Mosher's amide elucidated using the cambridge structural database.
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 θ1 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 θ2 of +21°; (5) the methyl group of the methoxy moiety was ap to the ipso-carbon atom of the phenyl group.
authors.affiliation: Division of Insect Sciences, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki 305-8634, Japan. ichikawa@affrc.go.jp.
authors.forename: Akio
authors.initials: A
authors.lastname: Ichikawa
authors.affiliation: Analytical Science Division, National Food Research Institute, Tsukuba, Ibaraki 305-8642, Japan. ono@affrc.go.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Ono
authors.affiliation: Department of Chemistry, Biology, and Environmental Science, Faculty of Science, Nara Women's University, Kita-Uoya Nishi-machi, Nara 630-8506, Japan. mikata@cc.nara-wu.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Mikata
mesh_terms: D000577:Amides / Q000737:chemistry*; D018360:Crystallography, X-Ray; D062126:Databases, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D010648:Phenylacetates / Q000737:chemistry*
chemical_list: D000577:Amides; D010648:Phenylacetates; C108322:Mosher's acid
keywords: MTPA; Mosher’s method; chiral recognition; chirality; crystal engineering