Benzohopanes and diaromatic 8(14)-secohopanoids in some Late Permian carbonates

We have detected a family of benzohopanes cyclised at C-20 and two families of diaromatic 8(14)-secohopanoids, in carbonates from the Late Permian Meishan (China) and Bulla (Italy) sections. Furthermore, we have identified a C ₃₃ 8(14)-secohopanoid possessing a fluorene moiety. The relative distribution of 8(14)-secohopanoids with a fluorene moiety was similar to that of benzohopanes cyclised at C-20, suggesting that the secohopanoids might be diagenetic products of benzohopanes, or that the benzohopanes and secohopanoids share the same precursor. Furthermore, the series of benzohopanes cyclised at C-16 was not detected from the carbonates of the two sections, which might suggest that the benzohopanes cyclised at C-16 are thermodynamically less stable than those with the aromatic ring attached at C-20.