Two new beta-class milbemycins from streptomyces bingchenggensis: fermentation, isolation, structure elucidation and biological properties.

Two new beta-class milbemycins from Streptomyces bingchenggensis, named milbemycin beta(13) and beta(14), have been isolated and characterized. The producing organism has been deposited at the China General Microbiology Culture Collection Center (Accession No: CGMCC1734). On the basis of detailed spectroscopic analysis and comparison with reported data, their structures were determined to be the hydroxyl derivatives at C-27 of milbemycin beta(3) and 25-ethylmilbemycin beta(3), respectively. Milbemycins beta(13) and beta(14) possess potent acaricidal and nematocidal activity. The discovery of these two compounds plays an important role in understanding and perfecting the proposed pathways of milbemycins.