Stereochemistry of atropisomeric 9,10-dihydrophenanthrene dimers from Pholidota chinensis

Yao, Sheng and Tang, Chun-Ping and Ye, Yang and Kurtán, Tibor and Kiss-Szikszai, Attila and Antus, Sándor and Pescitelli, Gennaro and Salvadori, Piero and Krohn, Karsten (2008) Stereochemistry of atropisomeric 9,10-dihydrophenanthrene dimers from Pholidota chinensis. Tetrahedron Asymmetry, 2008 (19). pp. 2007-2014. ISSN 0957-4166

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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.

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