5469-25-0Relevant articles and documents
Asymmetric synthesis of 2-substituted butane-1,4-diols by hydrogenation of homochiral fumaramide derivatives
Jawaid, Samaila,Farrugia, Louis J.,Robins, David J.
, p. 3979 - 3988 (2007/10/03)
Diastereoselective hydrogenation of homochiral fumaramides 1 derived from (2R)-Oppolzer's sultam was observed by analysis of the 1H NMR spectra of the succinamide mixtures with de's of 77-88%. Reduction of these succinamides using LiAlH4 gave the corresponding (2S)-butane-1,4- diols and established that addition of hydrogen takes place selectively on the re-face of fumaramides 1. The stereoselectivity was confirmed by estimating the ee's from the 19F NMR spectra of the Mosher's diesters of the diols. This methodology was applied to the synthesis of selected pyrrolidine natural products in homochiral form.
Preparation and Characterization of [5-13C]-(2S,4R)-Leucine and [4-13C]-(2S,3S)-Valine - Establishing Synthetic Schemes to Prepare Any Site-Directed Isotopomer of L-Leucine, L-Isoleucine and L-Valine
Siebum, Arjan H. G.,Woo, Wei Sein,Lugtenburg, Johan
, p. 4664 - 4678 (2007/10/03)
In this paper a chemo-enzymatic method has been developed that gives access to any isotopomer of the essential amino acids isoleucine and valine. The method gives the correct introduction of the second chiral center in (2S,3S)-isoleucine and allows for discrimination between the two prochiral methyl groups in valine as shown by the preparation of (2S,3S)-[4- 13C] valine. For the preparation of (2S)-leucine in any isotopomeric form, the O'Donnell method to prepare optically active amino acids has been used. The protected glycine scaffold used in this method has been prepared by a strategy that allows access to any isotopomeric form. The preparation of [5-13C]-(2S,4R)-leucine shows that the O'Donnell method in combination with the Evans method to obtain chiral 2-methylpropyl iodide leads to a good discrimination between the two prochiral methyl groups. The O'Donnell strategy for the preparation of α-amino acids is preferred over other methods since the reaction conditions are mild, the chiral auxiliary can be easily recovered and the optically active product can be easily separated. For the preparation of isotopically enriched valine and isoleucine the O'Donnell method is not suitable, because the alkyl substituents involved have a secondary halide substituent which is sterically too hindered to give an effective reaction with the protected glycine. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
Preparation of (S)-2-Substituted Succinates by Stereospecific Reductions of Fumarate and Derivatives with Resting Cells of Clostridium formicoaceticum
Eck, Richard,Simon, Helmut
, p. 13631 - 13640 (2007/10/02)
Fumarate derivatives have been reduced to (S)-2-methylsuccinate 2a, (S)-2-ethylsuccinate 3a and (S)-2-chlorosuccinate 4a in up to 1 M concentrations with Clostridium formicoaceticum.Formate was the electron donor and viologens or anthraquinone-2,6-disulphonate acted as artificial electron mediators.Reductions with freeze-dried cells in 2H2O-buffers led to the (2R,3S)--dideuterated succinate derivatives.The productivity numbers ranged from 450 to 5000 and the enantiomeric excess of all (S)-2-substituted succinates was >/= 99percent.
Mechanism of the Enzymic Elimination of Ammonia from 3-Substituted Aspartic Acids by 3-Methylaspartase
Botting, Nigel P.,Akhtar, Mahmoud,Cohen, Mark A.,Gani, David
, p. 1371 - 1373 (2007/10/02)
Kinetic experiments with 3-methylaspartase, using aspartic, 3-methylaspartic, and 3-ethylaspartic acid and the appropriate C-3 deuteriated isotopomers as substrates, reveal that C(3)-H bond cleavage is partially rate-limiting for 3-methylaspartic acid, much less rate-limiting for 3-ethylaspartic acid, and not rate-limiting at all for aspartic acid.
