Syntheses of both the putative and revised structures of aeruginosin EI461 bearing a new bicyclic alpha-amino acid.

[structure: see text] The putative structure of the naturally occurring aquatic peptide aeruginosin EI461 has been prepared from d-tyrosine. A corrected structure for aeruginosin EI461 is proposed, and the structure is proven by synthesis, which was accomplished using the new alpha-amino acid (2S,3aR,6R,7aR)-6-hydroxy-2-carboxyoctahydroindole, prepared from l-tyrosine. Succesive couplings of the dipeptide d-Leu-3a,7a-diepi-l-Choi with l-Hpla and NH(4)OH and a deprotection step gave aeruginosin EI461.

Synthesis of microcin SF608.

The first total synthesis of aquatic peptide microcin SF608 is described. Coupling of L-Hpla with the dipeptide L-Phe-L-Choi followed by coupling with agmatine and a deprotection step gave microcin SF608. In addition, the levorotatory character of L-Hpla (5) was thoroughly established, and the conformational analysis of L-Choi containing peptides 1 and 8-10 was performed using NMR spectroscopy to examine the cis-trans isomer equilibrium of the L-Phe-L-Choi amide bond.