Structures of New Alkaloids from Rain Forest Trees Galbulimima belgraveana and Galbulimima baccata in Papua New Guinea, Indonesia, and Northern Australia

Following on our
60-year research on the chemical constituents
of the rain forest trees Galbulimima belgraveana and Galbulimima baccata, we report
the isolation of seven new alkaloids: GB14 (14), GB22
(15), GB25 (16), GB21 (17),
GB23 (18), GB24 (19), and GB26 (20). Their structures were elucidated by a combination of spectroscopic
analyses and single-crystal X-ray crystallography, as well as structure
degradation and interconversion. The newly isolated alkaloids are
precursors or derivatives of the known family members from our early
studies and could be intermediates in the biosynthesis of the Galbulimima alkaloids. Therefore, the present study
has expanded the range of structures in this family of alkaloids and
provided some missing links in the biosynthetic sequences.