Phomoidrides E-G, three dimeric anhydrides from the fungus Pleosporales sp. give new insight to the biosynthesis of phomoidrides

Three phomoidride-type dimeric anhydrides, phomoidrides E-G (1-3), were isolated from the fungus Pleosporales sp. Their structures were elucidated by comprehensive spectroscopic analyses. Phomoidride E (1) possesses a totally new caged tricyclo[5.3.2.0(2;8)]dodecane carbon skeleton with a newly formed five-membered bridged ring through a C-C bond. Phomoidride F (2) features a unique caged ring system containing a bicyclo[4.3.1]deca-2,6-diene fused with an additional gamma-lactone ring. The identification of 1-3 offers new insight into phomoidride biosynthesis, where a new dimerization strategy with a key Claisen-like intermediate M1 instead of the previously proposed aldol-like product could be involved. 1 shows potent inhibitory activity against the HeLa cell line with an IC50 value of 1.41 mu M.

Automated summary

Three phomoidride-type dimeric anhydrides were isolated from the fungus Pleosporales sp., with structures elucidated by spectroscopic analyses. These compounds offer new insight into phomoidride biosynthesis and exhibited potent inhibitory activity against HeLa cell line.