Peculiar Stability of Amino Acids and Peptides from a Radical Perspective
作者:Zachary I. Watts、Christopher J. Easton
DOI:10.1021/ja9027583
日期:2009.8.19
Photochemical reactions of free and N-acetyl alpha-amino acids with chlorine and deuterium labeled hydrogen peroxide have been used to determine both the relative rates of reaction of molecules of these classes and the relative reactivity of their different types of hydrogen toward abstraction by chlorine and oxygen centered radicals. The relative rates of reaction of these species range over more than 3 orders
The present invention is directed to a new class of 4-(oxoalkyl)phosphono, 4(oxime alkyl)phosphono, or 4-(hydrazine alkyl)phosphono, 2-piperazine carboxylic derivatives that are useful as NMDA antagonists
Syntheses of (2S,3R)- and (2S,3R)[3-2h]- 3-methylaspartic acid: slow substrates for a syn-elimination reaction catalysed by methylaspartase.
作者:Catherine H. Archer、Neil R. Thomas、David Gani
DOI:10.1016/s0957-4166(00)80221-9
日期:1993.6
Mediylaspartase catalyses the slow syn-elimination of ammonia from the (2S,3R)-[L-erythro]-diastereomer of the natural substrate, (2S,3S)-3-methylaspartic acid, to give mesaconic acid. To provide material of sufficient stereochemical purity to probe the mechanism of the reaction, two synthetic routes to (2S,3R)- and (2S,3R)[3-H-2]- 3-methylaspartic acid were devised. The use of these (2S,3R)-3-methylaspartic acids revealed that the enzymic reaction does not involve C-3 epimerisation followed by normal anti-elimination, ruling-out the possibility of a carbanion intermediate. Conversely, the substrate displayed very large primary deuterium isotope effects indicating rate-limiting C-H bond cleavage.
Kinetics and mechanism of syn-elimination of ammonia from (2S,3R)-3-methylaspartic acid by methylaspartase
作者:Catherine H. Archer、David Gani
DOI:10.1039/c39930000140
日期:——
Methylaspartase catalyses the slow syn-elimination of ammonia from the (2S,3R)-[L-erythro]-diastereoisomer of the natural substrate (2S,3S)-3-methylaspartic acid, to give mesaconic acid; the reaction does not involve C-3 epimerisation followed by normal anti-elimination, ruling-out the possibility of a carbanion intermediate, but, displays large primary deuterium isotope effects consistent with concerted C–H and C–N bond cleavage.
Continued investigation of the polar extracts of the marine spongeLatrunculia sp. has resulted in the discovery of callipeltins J–M. The new structures were determined by interpretation of their NMR and MS data. The stereochemistry of the unusual 3-methylglutamine residue in callipeltins J and K was secured by stereoselective synthesis and Marfey's LC–MS analysis.