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Salmycin A–D, Antibiotics from Strep tomy ces violaceus, DSM 8286, Having a Siderophor-Aminoglycoside Structure

Salmycin B (2) and C (3) were isolated under acid conditions, under which they are stable, from the culture broth of Streptomyces violaceus, DSM 8286. The acid- and alkaline-labile, native main component salmycin A (1), as well as salmycin D (4), were obtained under strictly neutral pH conditions. The compounds 1 (C41H70FeN7O21), 2 (C41H69FeN6O21), 3 (C40H67FeN6O21), and 4 (C40H68FeN7O21) are classified as sideromycins and are stable when dry. Mild alkaline hydrolysis of 1 and 2 yielded the known siderophor danoxamin (5; C27H46FeN5O11), and amino-disaccharides. The amino-glycoside 6 (C14H25NO11) of salmycin B was stabilized by hydrogenation and the structure of the corresponding peracetate 10 determined by 1H,1H- and 1H,13C-correlation NMR spectroscopy (Table 1). Compound 6 consists of a glucos-2-ulose unit which is linked to the 2-position of a 6-deoxy-6-(methylamino)heptopyranose. The danoxamin is bonded via the carboxy group by ester linkage to the primary alcohol of the glucos-2-ulose. Salmycin A (1) is a natural oxime of 2, it was synthesized from 2 with hydroxylamine. The salmycins and those derivatives which contain hexapyranos-2-ulose form stable ketone hydrates which can be identified by mass spectrometry. Although several recently identified features of the danomycins do not correspond with those of the salmycins, 13C-NMR spectra show that both groups of antibiotics are closely related. All salmycins, especially component 1, are highly active against Staphylococci and Streptococci, even against resistant strains of these pathogens.