L-Valine → (S)-2-(4-bromobenzyl)amino-3-methylbutyric acid

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EP 1777224 describes the condensation of p-Bromobenzaldehyde with L-valine followed by reduction with sodium borohydride to give (S)-2-(4-bromobenzyl)amino-3-methylbutyric acid. (S)-2-(4-bromobenzyl)amino-3-methyl butyric acid is treated with valerylchloride to give (S)-2-(4-bromobenzyl)-pentanoyl-amino-3-methyl butyric acid. (S)-2-(4-bromobenzyl)-pentanoyl-amino-3-methyl butyric acid is treated with 2-(2H-tetrazol-5-yl)benzene-boronic acid in tetrahydrofuran, triphenylphosphine and palladiumacetate yield valsartan.

Provenance & Evidence