1 Stereochemistry of atropisomeric 9,10-dihydrophenanthrene dimers from Pholidota chinensis Sheng Yao, a Chun-Ping Tang, a Yang Ye, a, * Tibor Kurtán, b Attila Kiss-Szikszai, b Sándor Antus, b,c Gennaro Pescitelli, d Piero Salvadori, d and Karsten Krohn e, * a State Key Laboratory of Drug Research, Shanghai Institute of Materia Medica, Chinese Academy of Sciences, 555 Zu-Chong-Zhi Road, Zhangjiang Hi-Tech Park, Shanghai 201203, P. R. China b Department of Organic Chemistry, University of Debrecen, P.O. Box 20, 4010 Debrecen, Hungary c Research Group for Carbohydrates of the Hungarian Academy of Sciences, University of Debrecen, P.O.B. 55, H-4010 Debrecen, Hungary d Dipartimento di Chimica e Chimica Industriale, Università di Pisa, via Risorgimento 35, I-56126 Pisa, Italy e Department of Chemistry, University of Paderborn, Warburger Strasse 100, 33098 Paderborn, Germany * Corresponding author. Tel.: +86 21 50806726; Fax: +86 21 50807088; e-mail: yye@mail.shcnc.ac.cn (Y. Ye); Tel.: +49 5251 60 2172; Fax: +49 5251 60 3245; e-mail: k.krohn@upb.de (K. Krohn) Abstract - Six bis-9,10-dihydrophenanthrene and 9,10-dihydrophenanthrene/(dihydro)stilbene derivatives, phochinenins G-L (1-6), were isolated from the whole plant of Pholidota chinensis. Their structures were elucidated on the basis of extensive spectroscopic investigations (1D, 2D NMR and HR-EIMS). Owing to the sterically hindered rotation around the biaryl axis, some of these biaryl compounds can exist as a pair of enantiomers, but were isolated as racemates. Computed inversion barriers of selected atropisomeric derivatives suggested that phochinenins K (5), gymconpin C (7) and flavanthrin (9) have optically stable atropisomers. Their racemates were separated by HPLC on an optically active stationary phase, and stereochemically characterized on-line by circular dichroism (CD) spectroscopy (LC-CD coupling), in conjunction with quantum-mechanics CD calculations. Keywords: Pholidota chinensis; Phochinenins G-L; Dimeric 9,10-dihydrophenanthrene derivatives; Atropisomerism; Circular dichroism (CD); LC-CD coupling; CD calculations.