“…It is well known that benzo [20,21]hopanes 4−7 (C 32−35 , 2) and benzo [16,17,21]hopanes 6,8,9 (C 31−35 , 3) are formed from compound 1 via the cyclization reactions at C20 and C16, respectively. Some compounds with fluorene and acenaphthene moieties (e.g., compounds 4 and 5) in coals should be partially produced from D-ring monoaromatic 8 (14)-secobenzo [20,21]hopanes 6,10,11 (C 32−35 , 6) and 8 (14)-secobenzo [16,17,21]hopanes 11,12 (C 31−35 , 7), which are produced from the corresponding benzohopanes (i.e., compounds 2 and 3) via aromatization and C8−C14 bond cleavage, respectively. Coals are rich in the compounds with two aromatic moieties linked by −(CH 2 ) n −, such as 1-benzylnaphthalene (8), but their origin is still unclear.…”