New Seco-milbemycins from Streptomyces bingchenggensis: Fermentation, Isolation and Structure Elucidation

Two new seco-milbemycins have been isolated and characterized from the Streptomyces bingchenggensis . On the basis of detailed spectroscopic analysis and comparison with the reported data of milbemycin β 14 , their structures were established to be the seco-milbemycins of milbemycin β 14 . However, milbemycin β 14 and the two new seco-milbemycins were not converted to each other during purification by silica gel column or storage in the MeOH extract at room temperature. The two new seco-milbemycins are the first discovered from milbemycin-producing microorganisms. They may play an important role in understanding and perfecting the proposed biosynthesis pathways of milbemycins.