239. “A Practical Synthesis of (2S, 3R)-3-Amino-2-methylpentanoic Acid from L-Aspartic Acid”
     Jefford, C.W.; McNulty, J.
     Helv. Chim. Acta 1994, 77, 2142-2146.

L-Aspartic acid by successive N-tosylation, anhydride formation, and reduction was converted into (3S)-3-(tosylamino)butano-4-lactone (4). Electrophilic methylation of 4, subsequent iodo-esterification and nucleophilic methylation, followed by saponification and deprotection, gave (2S, 3R)-3-amino-2-methylpentanoic acid (2) with an ee of > 99% in seven steps and in an overall yield of 34%.

DOI : 10.1002/hlca.19940770807 

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