Double Bond Geometric Isomers of Pentaketide Ansamycins from Streptomyces sp. S008.

Six new pentaketide ansamycins, namely, shengliangmycins A-F (-, respectively), were obtained from the fermentation products of sp. S008OE that was derived by constitutive expression of LAL regulator gene . The structures of - were determined through comprehensive spectroscopic analysis and single-crystal X-ray diffraction. Compound has a -C6═C7 bond, which is different from that of compounds -. Compounds - feature a morpholinone structural moiety, whereas is characterized by a pyrazoline ring, which is rare in natural products.