Isolation and Identification of Two Novel Condensed Aromatic Lactones from Zhundong Subbituminous Coal

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Zhundong subbituminous coal was extracted with isometric carbon disulfide (CDS) and acetone mixed solvent (IMCDSAMS) to obtain the extract (EM). EM was fractionated with petroleum ether (PE), CDS, methanol, acetone, IMCDSAMS, and tetrahydrofuran to obtain the sub-extracts 1–6 (ES1–ES6), respectively. ES2 was sequentially eluted with PE and 30, 50, and 70% CDS/PE mixed solvents through a silica-gel-packed column to obtain eluted fractions 1–4 (EF1–EF4). A series of condensed aromatic lactones (CALs) were detected in EF4. Among them, 5H-phenanthro[1,10,9-cde]chromen-5-one and 4H-benzo[5,10]anthra[1,9,8-cdef]chromen-4-one were further isolated as nearly pure compounds by gelatin column chromatography and identified by gas chromatography/mass spectrometry, atmospheric solid analysis probe/time-of-flight mass spectrometry, Fourier transform infrared spectrometry, 1H nuclear magnetic resonance spectrometry, and 1H–1H correlation spectrometry. Main fragmental ions in the mass spectrum of each CAL are formed by successive losses of m/z 28 (CO) and 29 (−CHO) from the molecular ion. An effective way to isolate CALs from low-rank coals was provided in this paper.