On marine bacteria, article 18. 2 '-chartreusin-monoacetate, a new natural product with unusual anisotropy effects from the marine isolate Streptomyces sp B5525, and its 4 '-isomer

The marine Streptomycete isolates B5342 and B5525 forms, beside large amounts of the antitumor antibiotic chartreusin (1a), two chartreusin monoacetates as trace components. Whereas the chemical shift of the acetate methyl in le is in the normal range, the methyl group of the 2"-acetate residue in 1b and also in the tetra- and pentaacetates shows an extreme upfield shift. The structures of the monoacetates were confirmed by extensive NMR experiments, the anisotropic shift is explained by semi-empirical calculations.