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.
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