2-tert-Butyl-3-methyl-2,3-dihydroimidazol- 4-one-N-oxide: A New Nitrone-Based Chiral Glycine Equivalent
摘要:
Cycloaddition reactions between a new homochiral imidazolone-derived nitrone afford cycloadclucts in high yield and with high stereoselectivity. Subsequent cycloadduct elaboration affords the gamma-lactones of gamma-hydroxy-alpha-amino acids as well as the optically pure amino acids themselves.
Carbon–carbon (C–C) bondformation is the fundamental reaction type in organic synthesis. Biocatalytic methods for C–C bondformation have been limited to a few types of enzymes. In this report, we demonstrated the capability of a PLP-dependent enzyme ApUstD performing both C–C bond activation and asymmetric C–C bondformation, which resulted in non-canonical γ-hydroxy-α-amino acids. The reaction showed
Kynureninase in Organic Synthesis: Preparation of <i>γ</i>-Hydroxy-<i>α</i>-l-Amino Acids
作者:Tsuyoshi Miura、Noriko Masuo、Yuki Fusamae、Tetsuya Kajimoto、Yoshiteru Ida
DOI:10.1055/s-1998-3137
日期:1998.6
Kynureninase, which is known to catalyze the transaldol reaction between benzaldehyde and kynurenine, accepted many kinds of other aromatic aldehydes and propargyl aldehydes as the substrates to afford novel γ-hydroxy-α-l-amino acids. The l-configuration of the α-carbons was confirmed by an enzymatic method using both d- and l-amino acid oxidases. The stereochemistry of the newly formed chiral center (γ-position) in major isomers was determined to be R-configuration by the observed NOEs in the NMR spectroscopy of lactones derived from the γ-hydroxy-α-l-amino acids.
Stereochemistry and mechanism of aldol reactions catalyzed by kynureninase
作者:Robert S. Phillips、Rajesh K. Dua
DOI:10.1021/ja00019a039
日期:1991.9
Kynureninase from Pseudomonas has been reported to catalyze aldol and retro-aldol reactions, in addition to the physiological hydrolytic cleavage of L-kynurenine to anthranilic acid and L-alanine. However, the stereochemistry of these novel aldol reactions has not been previously determined. We have determined that the reaction of L-kynurenine and benzaldehyde catalyzed by kynureninase results in (2S,4R)-2-amino-4-hydroxy-4-phenylbutanoic acid. Similarly, the 4R isomer of dihydro-L-kynurenine readily undergoes retro-aldol cleavage, while the 4S isomer is unreactive as a substrate. Both isomers of dihydro-L-kynurenine are competitive inhibitors of kynureninase from Pseudomonas. However, the 4S isomer of dihydro-L-kynurenine is the most potent inhibitor, with a K(i) of 0.3-mu-M. These results provide additional support for a general base mechanism for kynureninase, and suggest that the hydration occurs on the re face of the carbonyl group of kynurenine to give an (S)-gem-diolate intermediate.
EP0581907A4
申请人:——
公开号:EP0581907A4
公开(公告)日:1994-04-06
INHIBITORS OF KYNURENINASE
申请人:THE UNIVERSITY OF GEORGIA RESEARCH FOUNDATION, INC.