Compounds 7′ and 6′-bromo-d-tryptophan (1 and 2) which are important derivatives for the synthesis of the chloropeptin and kistamycin A, respectively, were conveniently synthesized by optical resolution from N-acetyl-7′ and 6′-bromo-dl-tryptophan ((RS)-5 and (RS)-14) using d-aminoacylase.