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Asymmetric synthesis of unusual amino acids: Synthesis of optically pure isomers of N-indole- (2-mesitylenesulfonyl)-β-methyltryptophan

✍ Scribed by Lakmal W. Boteju; Kirsten Wegner; Xinhua Qian; Victor J. Hruby

Publisher: Elsevier Science
Year: 1994
Tongue: French
Weight: 984 KB
Volume: 50
Category: Article
ISSN: 0040-4020
DOI: 10.1016/s0040-4020(01)86957-x

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✦ Synopsis

We have developed methods for the synthesis of the four optically pure isomers of B-methyltryptophan with the 2-mesitylenesulfonyl indole protecting group for peptide synthesis. Starting from 3-indoleacrylic acid, the Bmethyl function was generated by a chiral auxiliary-directed asymmetric conjugate 1,Caddition. Asymmetric bromination was achieved via a tandem addition of N-bromosuccinimide to the enolate formed by the conjugate addition. Displacement of the bromide by axide, hydrolysis of the chiral auxiliary and then reduction, led to the two erythro isomers. Chiral imide enolate azidation of the conjugate adduct, hydrolysis of the chiral auxiliary and reduction yielded the two rhreo isomers in high optical purity.

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