M.S. Abidi S. L. Abidi 1983 The ¹³C nuclear magnetic resonance (nmr) spectra of epimers of rotenone and four 12a-hydroxy-analogues were examined to determine the stereochemical effect of the B/C ring fusion involving the 6a- and 12a-carbon centers. Chemical shift differences between the epimeric carbon resonances of cis- and trans-6a,12a-compounds were notably larger than those of diastereoisomers derived from the same B/C ring junction stereochemistry. Results of the spectral analysis have been useful for the quantification of mixtures of epimers and for the measurement of rates of epimerization and oxygenation. application/pdf 10.1002/jhet.5570200649 en Wiley 13C NMR spectral characterization of epimeric rotenone and some related tetrahydrobenzopyranofurobenzopyranones article