Component Amino Acids of the Antibiotic Longicatenamycin. Isolation of 5-Chloro-d-tryptophan

An amino acid composition of the pep tide antibiotic longicatenamycin was investigated. Four new amino acids, i.e., thero-β-hydroxy-l-glutamic acid, l-2-amino-5-rnethylhexanoic acid, l-2-amino-6-methylheptanoic acid, and l-2-amino-7-methyloctanoic acid, which were reported by Shoji et al., were reconfirmed by comparison with the synthetic specimens. Racemic forms of the latter three amino acids were synthesized through acetaminomalonate method. Furthermore, 5-chloro-d-tryptophan was newly isolated from the hydrolyzate of the antibiotic. This structure was assigned by NMR, MS and ORD. A steric configuration of this amino acid was certified by degradation to d-aspartic acid through ozonization. 5-Chloro-Dl-tryptophan was synthesized from 3-cyanopropionaldehyde and p-chlorophenylhydrazine by Fischer’s indole synthesis.