1. Efficient Chemoenzymatic Synthesis of (2 S,3 R)-3-Hydroxy-3-Methylproline, a Key Fragment in Polyoxypeptin A and FR225659
Xiao Zhang, Hans Renata Tetrahedron. 2019 Jun 14;75(24):3253-3257. doi: 10.1016/j.tet.2019.04.009. Epub 2019 Apr 5.
We report an efficient synthesis of protected (2S,3R)-3-hydroxy-3-methylproline that proceeds in three steps with complete stereoselectivity. This route represents a significant improvement over previous approaches to this noncanonical amino acid. Key to this success is the development of a one-pot chemoenzymatic procedure for the preparation of (2S,3S)-3- methylproline from L-isoleucine. This work lays the foundation for future chemoenzymatic syntheses of polyoxypeptin A and FR225659.
2. Preparation of optically active threo-2-amino-3-hydroxy-3-phenylpropanoic acid (threo-beta-phenylserine) via optical resolution
Tadashi Shiraiwa, Reiichi Saijoh, Masahiro Suzuki, Kyosuke Yoshida, Satoshi Nishimura, Hisashi Nagasawa Chem Pharm Bull (Tokyo). 2003 Dec;51(12):1363-7. doi: 10.1248/cpb.51.1363.
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.
3. (2S,3R)-2-[(4-Ethyl-2,3-dioxopiperazin-1-yl)carbonyl-amino]-3-hydroxy-butyric acid monohydrate
Chun-Xiang Ji, Yong-Tao Cui, Dong-Ling Yang, Cheng Guo Acta Crystallogr Sect E Struct Rep Online. 2008 Jun 19;64(Pt 7):o1292. doi: 10.1107/S1600536808017832.
In the title compound, C(11)H(17)N(3)O(6)·H(2)O, an important building block of the medicine cefbuperazone sodium, the piperazine ring adopts a screw-boat conformation. Inter-molecular O-H⋯O and intra-molecular N-H⋯O hydrogen bonds are observed. The water mol-ecule participates as both donor and acceptor in this framework.
