STUDY OF CONFORMATIONAL PREFERENCES OF ERYTHRO- CAROLIGNAN E ASSESSED BY THE COUPLING BETWEEN H7'-H8' IN DIFFERENT NMR SOLVENTS

Erythro -carolignan E ( 1 ) has been obtained from the ethanol extract of the wood bark of  Durio affinis  Becc. This research was conducted in order to prove that conformational preferences of compound  1  were solvent dependent. On the basis of  1 H-NMR data, the relative configuration of compound  1  was characterized by a coupling constant ( 3 J HH ) value of 3.3 Hz at H-7' in CDCl 3 . The coupling constant ( 3 J HH ) values of H-7' in compound  1  has changed to 4.1 Hz and 5.3 Hz in pyridine- d 5  and acetonitrile- d 3  respectively. As a result, the conformation of compound  1  at C7'-C8' has changed in different NMR solvents.  In conclusion, structure of erythro -carolignan E that contains a dihydroxy group at C7'-C8' is able to change in different NMR solvent.

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