Carexanes from Carex distachya Desf.: revised stereochemistry and characterization of four novel polyhydroxylated prenylstilbenes

Carexanes are unusual secondary metabolites isolated from the herbaceous plant Carex distachya. Four new carexanes have been isolated and characterized from the methanolic leaf extract of the plant. All of the structures have been elucidated on the basis of spectroscopic data. The stereochemistry of all the carexane metabolites isolated from the plant, as well as their 1H and 13C NMR spectroscopic assignment, has been revised on the basis of X-ray analysis of carexane D, chemical correlations, and NOESY/ROESY experiments. All the data suggested a cis junction between B and C rings.