The structures of three new Galbulimima alkaloids

The structures of three new alkaloids isolated from the bark of the rain forest tree Galbulimima belgraveana, have been determined by a combination of NMR spectroscopy and X-ray crystallography. One of the alkaloids, himgrine (5), was shown to be an oxygenated derivative of himbacine (1), while the second, GB16, (8) proved to be identical with a degradation product from himgaline (4). The remaining alkaloid, GB17 (12) possesses an entirely new and unexpected skeleton.