Palau'amine and Its Congeners:  A Family of Bioactive Bisguanidines from the Marine Sponge Stylotella aurantium¹

Abstract

The strongly cytotoxic, antibiotic, and immunosuppressive palau'amine was isolated from the Belau sponge Stylotella aurantium, along with less active 4-bromo and 4,5-dibromo derivatives. Three corresponding isomeric compounds, all less active, were also isolated, and full details of the isolation and all structure proofs are provided.

Structure of debromo-carteramine A, a novel bromopyrrole alkaloid from the Mediterranean sponge Axinella verrucosa

“…[1][2][3][4][5][6][7] Historically, these compounds, which have been found only in the marine environment to date, have attracted the attention of natural product chemists because of their structural complexity. Today, the interest is sparked not only by the wide structural diversity, ranging from simple molecules like oroidin 8,9 to complex structures like palau'amine 10,11 and stylissadine A and B, 12 but also by their organic synthesis, 13 bio-synthesis, 14 and pharmacological activities. 6,7,15 Furthermore, these compounds have a chemo-ecological interest due to their role in chemically mediated interactions such as in the chemical defense against predators 16,17 and fouling organisms.…”

Asymmetric Synthesis of Axinellamines A and B

“…[7,8,[14][15][16][17] Previously, we used the 10′-hydroxy group of 4 (protected ent-10′-hydroxydibromoageliferin) to set up the desired spiro-configuration of 2a through directed oxidation.…”

“…Romo and co-workers subsequently disclosed an oxidative ring-contraction approach that was inspired by Scheuer's biosynthetic hypothesis. [7,17] This skeletal rearrangement reaction has also been studied by Lovely et al [8] The total synthesis of 1 was accomplished by the Baran group by using two different approaches. [3][4][5] The group first used an intramolecular aldol reaction to construct the cyclopentyl core of 1.…”

“…[7,8,[14][15][16][17] Previously, we used the 10′-hydroxy group of 4 (protected ent-10′-hydroxydibromoageliferin) to set up the desired spiro-configuration of 2a through directed oxidation. [15] However, we were not able to convert this hydroxy directing group into a chloride at a late stage to achieve the synthesis of 1.…”

Investigations of the Marine Flora and Fauna of the Islands of Palau

“…117 Chemistry/bioactivity: the bisguanidine alkaloid palau'-amine 162 was isolated from the 1991 collection of S. agminata 118 with five additional related metabolites being reported by workers from the same group in 1998 when the taxonomy was revized. 117 Palau'amine is relatively non-toxic in mice but is cytotoxic to P-388 and A549 cells. It is also antimicrobial and antifungal and showed promise in an immunomodulatory assay.…”