Preparation of optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (threo-beta-phenylserine) via optical resolution.
To obtain optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (1), (2RS,3SR)-2-benzoylamino-3-hydroxy-3-phenylpropanoic acid [(2RS,3SR)-2] was first optically resolved using (1S,2S)- and (1R,2R)-2-amino-1-(4-nitrophenyl)-1,3-propanediol as the resolving agents to afford (2R,3S)- and (2S,3R)-2 in yields of 73% and 66%, based on half of the starting amount of (2RS,3SR)-2. Next, the racemic structures of ammonium and some organic ammonium salts of (2RS,3SR)-2 were examined based on melting point, solubility, and infrared spectrum, with the aim of optical resolution by preferential crystallization. The benzylammonium salt of (2RS,3SR)-2 was suggested to exist as a conglomerate at room temperature, although it forms a racemic compound at the melting point. The optical resolution by preferential crystallization of the racemic salt afforded the (2R,3S)- and (2S,3R)-salts with optical purities of 90-97%. The (2R,3S)- and (2S,3R)-2 obtained from the purified salts were hydrolyzed by reflux in hydrochloric acid to give (2R,3S)- and (2S,3R)-1.
Shiraiwa
Tadashi
T
Unit of Chemistry, Faculty of Engineering and High Technology Research Center, Kansai University, Suita, Osaka, Japan. shiraiwa@ipcku.kansai-u.ac.jp
Saijoh
Reiichi
R
Suzuki
Masahiro
M
Yoshida
Kyosuke
K
Nishimura
Satoshi
S
Nagasawa
Hisashi
H
D003460:Crystallization; D007536:Isomerism; D055095:Optics and Photonics; D012694:Serine / Q000031:analogs & derivatives* / Q000032:analysis / Q000138:chemical synthesis*
D012694:Serine; C467259:phenylserine