title: Structures and properties of a diastereoisomeric molecular compound of (2S,3S)- and (2R,3S)-N-acetyl-2-amino-3-methylpentanoic acids.
abstract: An X-ray crystal structural analysis revealed that (2S,3S)-N-acetyl-2-amino-3-methylpentanoic acid (N-acetyl-L-isoleucine; Ac-L-Ile) and (2R,3S)-N-acetyl-2-amino-3-methylpentanoic acid (N-acetyl-D-alloisoleucine; Ac-D-aIle) formed a molecular compound containing one Ac-L-Ile molecule and one Ac-D-aIle molecule as an unsymmetrical unit. This molecular compound is packed with strong hydrogen bonds forming homogeneous chains consisting of Ac-L-Ile molecules or Ac-D-aIle molecules and weak hydrogen bonds connecting these homogeneous chains in a fashion similar to that observed for Ac-L-Ile and Ac-D-aIle. Recrystallization of an approximately 1:1 mixture of Ac-L-Ile and Ac-D-aIle from water gave an equimolar molecular compound due to its lower solubility than that of Ac-D-aIle or especially Ac-L-Ile. The results suggest that the equimolar mixture of Ac-L-Ile and Ac-D-aIle could be obtained from an Ac-L-Ile-excess mixture by recystallization from water.
authors.affiliation: Faculty of Chemistry, Materials and Bioengineering, Kansai University, Suita, Osaka, Japan. t.yajima@ipcku.kansai-u.ac.jp
authors.forename: Tatsuo
authors.initials: T
authors.lastname: Yajima
authors.forename: Makiko
authors.initials: M
authors.lastname: Kimura
authors.forename: Mami
authors.initials: M
authors.lastname: Nakakoji
authors.forename: Takao
authors.initials: T
authors.lastname: Horikawa
authors.forename: Yurie
authors.initials: Y
authors.lastname: Tokuyama
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shiraiwa
mesh_terms: D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007532:Isoleucine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification; D008958:Models, Molecular; D008968:Molecular Conformation; D010421:Pentanoic Acids / Q000737:chemistry* / Q000302:isolation & purification; D000644:Quaternary Ammonium Compounds / Q000737:chemistry; D012492:Salts / Q000737:chemistry; D012995:Solubility; D013237:Stereoisomerism
chemical_list: C546780:N-acetyl-2-amino-3-methylpentanoic acid; D010421:Pentanoic Acids; D000644:Quaternary Ammonium Compounds; D012492:Salts; D007532:Isoleucine