Herein, we report our results on the synthetic studies of the originally proposed structure of protoaculeine B, isolated from a marine sponge. Starting from tryptophan, two candidates of the suitably protected heterotricyclic subunits were stereoselectively synthesized over 8 and 16 steps, respectively. Furthermore, two diastereomeric heterotricyclic amino acids, finally synthesized, were found to be neuroactive: the (9S*,11S*)-isomer with natural-type configuration was hyperactive, whereas diastereomeric (9S*,11R*)-isomer was hypoactive upon mice intracerebroventricular injection.

Polyamines are ubiquitously found in nature. In this paper, we disclose our iterative coupling strategy for the synthesis of structurally defined polymer of 1,3-propanediamine, the polymer can be used for...