In the course of our continuing studies of the genus Kopsia,
1–8 we obtained small amounts of a new alkaloid, valparicine
1, from the stem–bark extract of K. arborea.
The alkaloid was obtained following repeated chromatographic
fractionation, as a colourless oil with [a]D
40 (c 0.22, CHCl3). The UV spectrum (EtOH) showed
absorptions at 228 and 297 nm indicating the presence
of an unsubstituted indolenine chromophore, which
was also supported by the presence of the characteristic
imine resonance at d 186 in the 13C NMR spectrum. The
EIMS of 1 showed a molecular ion at m/z 276, which
analyzed for C19H20N2, differing from pericine 2,
another alkaloid also present, by loss of two hydrogens.
9 The 13C NMR spectrum (Table 1) gave a total
of 19 carbon resonances (one methyl, five methylenes,