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Syntheses of (2S,3R)- and (2S,3R)[3-2h]- 3-methylaspartic acid: slow substrates for a syn-eliminatio

Syntheses of (2S,3R)- and (2S,3R)[3-2h]- 3-methylaspartic acid: slow substrates for a syn-eliminatio

  1. chaos69
    Catherine H. Archera, Neil R. Thomasa and David Gani,

    Tetrahedron: Asymmetry
    Volume 4, Issue 6, June 1993, Pages 1141-1152

    Abstract

    Methylaspartase 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)[3-2H]- 3-methylaspartic acid were devised. The use of these (2S,3R)-3-methylaspartic adds 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.

    (2S,3R)- and (2S,3R)[3-2H]-3-methylaspartic acid were prepared via enzymatic and non-enzymatic routes were used to probe the mechanism of methylaspartase

    NOTE: Contains high yield synth of alpha-bromopropanoic acid from alanine