The Natural Product Essramycin and Three of Its Isomers Are Devoid of Antibacterial Activity

Four possible isomers of essramycin,
a natural product from a marine Streptomyces species
isolated from the Egyptian Mediterranean
coast, were synthesized. The structures for the isomers were assigned
unequivocally by 1H NMR, 13C NMR, high-resolution
mass spectrometry, and X-ray crystal structure determinations. Notwithstanding
the earlier report of broad-spectrum antibacterial activity for the
natural product, none of the four isomers exhibited any such activity.