65718-51-6Relevant academic research and scientific papers
Peptide-catalyzed conversion of racemic oxazol-5(4 H)-ones into enantiomerically enriched α-amino acid derivatives
Metrano, Anthony J.,Miller, Scott J.
, p. 1542 - 1554 (2014/03/21)
We report the development and optimization of a tetrapeptide that catalyzes the methanolytic dynamic kinetic resolution of oxazol-5(4H)-ones (azlactones) with high levels of enantioinduction. Oxazolones possessing benzylic-type substituents were found to perform better than others, providing methyl ester products in 88:12 to 98:2 er. The mechanism of this peptide-catalyzed process was investigated through truncation studies and competition experiments. High-field NOESY analysis was performed to elucidate the solution-phase structure of the peptide, and we present a plausible model for catalysis.
Rate constants for 1,n-hydrogen transfer reactions in some amino acid derived radicals
Zeng, Le,Kaoudi, Talbi,Schiesser, Carl H.
, p. 7911 - 7914 (2007/10/03)
Absolute rate constants for 1,n-hydrogen atom transfers in some substituted amino acid derived radicals have been determined in benzene through the use of competitive kinetic experiments. Radicals derived from methyl N-(2-iodobenzoyl)-N-(tert-butyloxycarbonyl)glycinate, -alaninate, -leucinate, -tert-leucinate and -phenylglycinate undergo intramolecular 1,5-hydrogen atom transfer to afford the corresponding α-amino acid ester radicals with rate constants in the range: 1.0-4.3 × 107 s-1 at 80 °C. Where abstractable hydrogen atoms exist in the amino acid side-chain, 1,6- and 1,7-translocations are competitive processes.
Nucleophilic acyl substitutions of anhydrides with protic nucleophiles catalyzed by amphoteric, oxomolybdenum species
Chen, Chien-Tien,Kuo, Jen-Huang,Pawar, Vijay D.,Munot, Yogesh S.,Weng, Shieu-Shien,Ku, Cheng-Hsiu,Liu, Cheng-Yuan
, p. 1188 - 1197 (2007/10/03)
(Chemical Equation Presented) Among six different group VIb oxometallic species examined, dioxomolybdenum dichloride and oxomolybdenum tetrachloride were the most efficient catalysts to facilitate nucleophilic acyl substitution (NAS) of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. In contrast to the well-recognized redox chemical behaviors associated with oxomolybdenum(VI) species, the catalytic NAS was unprecedented and tolerates virtually all kinds of functional groups. By using benzoic anhydride as a mediator for in situ generation of an incipient mixed anhydride-MoO2Cl2 adduct with a given functional alkanoic acid, one can achieve oleate, dipeptide, diphenylmethyl, N-Fmoc-α-amino, pyruvic, and tert-butylthio ester, N-tert-butylamide, and trityl methacrylate syntheses with appropriate protic nucleophiles. The amphoteric character of the Mo=O unit in oxomolybdenum chlorides was found to be responsible for the catalytic NAS profile as supported by a control NAS reaction of using an authentic adduct-MoOCl2(O2-CBu t)2 between pivalic anhydride and MoO2Cl 2 as the catalyst.
Synthesis of homochiralL-(S)-tert-leucine via a lipase catalysed dynamic resolution process
Turner, Nicholas J.,Winterman, James R.,McCague, Raymond,Parratt, Julian S.,Taylor, Stephen J. C.
, p. 1113 - 1116 (2007/10/02)
Treatment of (±)-2-phenyl-4-tert-butyloxazolin-5(4H)-one 8 with Lipozyme (Mucor miehei) in toluene containing n-butanol and a catalytic amount of triethylamine resulted in a 94% yield of (S)-N-benzoyltert-leucine butyl ester 9 (99.5% e.e.). Subsequent two step hydrolysis (Alcalase followed by 6N HCl, reflux) yielded homochiral L-(S)-tert-leucine 1.
