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

Abstract

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 ¹H-NMR data, the relative configuration of compound 1 was characterized by a coupling constant (³J_HH) value of 3.3 Hz at H-7' in CDCl₃. The coupling constant (³J_HH) values of H-7' in compound 1 has changed to 4.1 Hz and 5.3 Hz in pyridine-d₅ and acetonitrile-d₃ respectively. As a result, the conformation of compound 1 at C7'-C8' has changed in different NMR solvents.  In conclusion, structure oferythro-carolignan E that contains a dihydroxy group at C7'-C8' is able to change in different NMR solvent.