title: Optical resolution by preferential crystallization of (RS)-2-benzoylamino-2-benzyl-3-hydroxypropanoic acid and its use in synthesizing optically active 2-amino-2-methyl-3-phenylpropanoic acid.
abstract: To synthesize optically active 2-amino-2-methyl-3-phenylpropanoic acid (1), (RS)-2-benzoylamino-2-benzyl-3-hydroxypropanoic acid [(RS)-2] was first optically resolved using cinchonidine as a resolving agent to yield optically pure (S)- and (R)-2 in yields of about 70%, based on half of the starting amount of (RS)-2. Next, the racemic structure of (RS)-2 was examined based on melting point, solubility, IR spectrum, and binary and ternary phase diagrams, with the aim of optical resolution by preferential crystallization of (RS)-2. Results indicated that the (RS)-2 exists as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization yielded (S)- and (R)-2 with optical purities of about 90%, which were fully purified by recrystallization. After O-tosylation of (S)- and (R)-2, reduction by zinc powder and sodium iodide gave (R)- and (S)-1, respectively.
authors.affiliation: Unit of Chemistry, Faculty of Engineering and High Technology Research Center, Kansai University, Suita, Osaka, Japan. shiraiwa@ipcku.kansai-u.ac.jp
authors.forename: Tadashi
authors.initials: T
authors.lastname: Shiraiwa
authors.forename: Masahiro
authors.initials: M
authors.lastname: Suzuki
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Sakai
authors.forename: Hisashi
authors.initials: H
authors.lastname: Nagasawa
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Takatani
authors.forename: Daisuke
authors.initials: D
authors.lastname: Noshi
authors.forename: Kenji
authors.initials: K
authors.lastname: Yamanashi
mesh_terms: D003460:Crystallization; D009904:Optical Rotation; D010666:Phenylpropionates / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D010666:Phenylpropionates