Epimeric (20<i>R</i>,20<i>S</i>)-Verazine Isolated from<i>Veratrum maackii</i>: Two-Dimensional NMR Studies and Total Assignment of¹H- and¹³C-Resonances

Abstract

(13)C-NMR evidence shows that verazine [(25 S)-iminocholesta-5,22( N)-diene-3beta-ol] isolated from the Chinese plant VERATRUM MAACKII (Melanthiaceae) consists of a 20 R/20 S mixture of epimers. The determination of the configurations at the chiral epimeric center and of the conformation of the 17beta-side chain is based on the total assignment of the (13)C- and (1)H-NMR resonances. This goal was achieved by the extensive use of homo- and heteronuclear shift correlation and two-dimensional NOE spectroscopy methods at high magnetic field.