URDAMYCINS, NEW ANGUCYCLINE ANTIBIOTICS FROM STREPTOMYCES FRADIAE

VI. STRUCTURE ELUCIDATION AND BIOSYNTHETIC INVESTIGATIONS ON URDAMYCIN H

Abstract

A new angucycline antibiotic has been discovered as a small side product of Streptomyces fradiae (strain Tü 2717), the producer of the urdamycin complex, during screening for biosynthetic relatives of urdamycins C and D.
The structure was elucidated after isolation, via strain selection, of a mutant of S. fradiae that produces this new congener in larger amounts.
The structure includes a new chromophore containing aglycone that has not been found before among the angucyclines nor as a natural product generally. In urdamycin H (1) the angucycline four-ring system is enlarged by a (p-OH-phenyl)furan moiety and is closely related to urdamycin C (2). The structure was elucidated by comparison of the physico-chemical data with those of known urdamycins, especially with those of urdamycin C (2), and was confirmed by intensive 2D NMR analysis.
Biosynthetic studies showed that tyrosine and not the smaller p-OH-phenylglycine is the precursor of the (p-OH-phenyl)furan moiety.