Wychimicins, a new class of spirotetronate polyketides from Actinocrispum wychmicini MI503-A4

In the course of our screening program for new anti-methicillin-resistant Staphylococcus aureus antibiotics, four novel antibiotics, termed wychimicins A–D, were isolated from the culture broth of the rare actinomycete Actinocrispum wychmicini strain MI503-AF4. Wychimicins are spirotetronates possessing a macrocyclic 13-membered ring containing trans-decalin and β-d-xylo-hexopyranose moieties connected to C-17 by an O-glycosidic linkage according to MS, NMR and X-ray analyses. In X-ray crystal structure analysis, the Flack constant was 0.10 (11). The stereochemistry of the spirocarbon C-25 was R. Wychimicins had a minimum inhibitory concentration of 0.125–2 µg ml(−1) against methicillin-resistant Staphylococcus aureus.