Synthesis of (2S,3S)-β-methyltryptophan

Nα-Fmoc-protected (2S,3S)-β-methyltryptophan has been synthesized by asymmetric synthesis through the aid of an oxazolidinone auxiliary. Coupling of the mixed anhydride of Nin-Boc-protected indoleacrylic acid to the oxazolidinone auxiliary was achieved by lithium bromide and N,N-dimethylpyridine (DMAP). This reaction is milder and more convenient to run than the traditional conditions using butyl lithium.