100415-25-6 → 100415-25-6

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Reaction Steps

The fermentation broth is separated from the biomass in conventional manner, e.g. by filtration or centrifugation, and the filtrate is extracted with a water-immiscible, or substantially water-immiscible, solvent, e.g. methylene chloride, chloroform or, preferably, ethyl acetate. The organic phase is evaporated under vacuum, affording a crude extract. This crude extract is partitioned in a two-phase system consisting of two immiscible organic solvents, e.g. methanol/heptane, and the fermentation products, in particular the antibiotics of formula I, become enriched in the polar phase. After removal of the polar solvent by evaporation, the residue is dissolved in dilute ammonia solution and washed with water-immiscible solvent, e.g. diethyl ether. The volatile ammonia is removed under vacuum and the aqueous phase, after acidification with an organic acid, e.g. formic acid or acetic acid, is extracted with one of the water-immiscible, or substantially water-immiscible, solvents mentioned above, e.g. methylene chloride. The resultant antibiotics are subsequently purified by reversed phase chromatography, affording several fractions which may contain sorangioside A and B in admixture or in pure form, and sorangicin A and B in admixture or in pure form. The individual components sorangioside A and B and sorangicin B are obtained by separation of the respective fractions by HPLC, whereas the main component, sorangicin A, can be obtained in crystalline form from the appropriate fraction.

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