Streptovaricin J

A new streptovaricin analogue, namely 3-desmethyl protostreptovaricin I (1), was isolated from the culture of the genetically engineered strain ΔstvM2 derived from Streptomyces spectabilis CCTCC M2017417. Its structure was elucidated on the basis of extensive spectroscopic analyses, including 1D and 2D NMR tests, and high resolution mass spectrometry analysis. Compound 1 is the first example of 3-desmethyl streptovaricin analogues reported so far, however, it showed no antibacterial activities against Staphylococcus aureus ATCC 29213.

[Carboxy-14C]-3-amino-5-hydroxybenzoic acid (AHBA) has been shown to be incorporated by Streptomyces spectabilis to the extent of greater than 0.1% (35: 1 dilution) in the ansamycin antibiotic streptovaricin C, the major component of the streptovaricin complex. When [carboxy-13C]AHBA was similarly administered, C-21 (quinone methide carbonyl at 188.3 ppm) of streptovaricin C was specifically labeled (at twenty one times natural abundance). In preparation for the 13C incorporation study the 13C NMR spectrum of streptovaricin C was investigated, making extensive use of short- and long-range HETCOR. These assignments revise some of those proposed earlier for streptovaricin C.

A new ring-fused streptovaricin analogue, named ansavaricin J, was unprecedently isolated from the culture of the genetically modified strains ΔstvP5 which derived from Streptomyces spectabilis CCTCC M2017417. Its structure was elucidated via comprehensive spectroscopic analyses, including 1D- and 2D-NMR tests, and HR-ESI-MS data analysis. Notably, ansavaricin J and E represent the only two reported examples of heterocyclic ring-fused streptovaricins thus far, however, it only showed insignificant antibacterial activities against Staphylococcus aureus.