合成路线1

Condensation of phenylacetic acid (XI) with methoxyamine gave hydroxamate (XII). After N-chlorination of (XII) with tert-butyl hypochlorite, Ag(I)-catalyzed ring closure of the intermediate (XIII) produced N-(methoxy)oxindole (XIV). Amide reduction of (XIV) with LiAlH4 gave hemiaminal (XV), which was converted to the racemic tryptophan derivative (XVII) by reaction with alpha-acetamidoacrylic acid (XVI) in AcOH-Ac2O. Optical resolution of (XVII) by enantioselective enzymatic hydrolysis of the acetamide group using Acylase I from Aspergillus sp. afforded N1'-methoxy-L-tryptophan (XVIII), which was protected as the N-Boc derivative (XIX) and N-methylated by means of MeI and NaH yielding (XX). The resulting N-methyl amino acid (XX) was esterified upon treatment with (trimethylsilyl)diazomethane giving (XXI), and the N-Boc group was removed with HCl in EtOAc to provide the tryptophan derivative (XXII).