Further novel milbemycin antibiotics from Streptomyces sp. E225. Fermentation, isolation and structure elucidation.

Ten novel alpha and beta class milbemycins have been isolated and characterized from the Streptomyces sp. E225, which has previously been shown to produce four related milbemycins. Some of the metabolites contain new structural features including, VM48641 which possesses an alpha-methoxyl substituent at C-27, and VM48642 which contains a furan ring at the terminus of the C-26 side chain. Several of these new compounds were shown to possess potent anthelmintic activity. An analysis of NMR chemical shift trends in this series of metabolites is presented.