Stereochemistry of the Modified Tryptophan Residues Contained in Konbamide and Keramamide a Isolated from Marine Sponges of the GenusTheonella

The absolute configurations of the unusual tryptophan-derived amino acid residues, 2-bromo-5-hydroxytryptophan and 6-chloro-5-hydroxy-N-methyltryptophan, contained in the cyclic peptides konbamide (1) and keramamide A (2), respectively, previously isolated from Okinawan marine sponges Theonella sp. were determined to be both L on the basis of chiral GC and HPLC analyses.