Miharadienes A–D with unique cyclic skeletons from a marine-derived Streptomyces miharaensis

Abstract

A new type of natural products, miharadienes A–D (1–4), was isolated from the marine-derived Streptomyces miharaensis 151KO-143. Their structures were elucidated using a combination of NMR spectroscopy, acid hydrolysis, modified Mosher's method, electronic circular dichroism (ECD) and single crystal X-ray diffraction data. Interestingly, compounds 1 and 4 featured an unusual 2,10-dioxabicyclo[5.3.1]undecane ring system and a rare 5/5 furo[3,4-c]furan ring system, respectively, and all compounds 1–4 possessed a E,E-diene moiety at a side chain. Miharadiene D (4) exhibited moderate inhibitory effect of nitric oxide production in lipopolysaccharide-stimulated BV-2 microglia cells.