Recent advances in lamellarin alkaloids: isolation, synthesis and activity

Lamellarins are a large family of marine alkaloids with potential anticancer activity that have been isolated from diverse marine organisms, mainly ascidians and sponges. All lamellarins feature a 3,4-diarylpyrrole system. Pentacyclic lamellarins, whose polyheterocyclic system has a pyrrole core, are the most active compounds. Some of these alkaloids are potently cytotoxic to various tumor cell lines. To date, Lam-D and Lam-H have been identified as lead compounds for the inhibition of topoisomerase I and HIV-1 integrase, respectively nuclear enzymes which are over-expressed in deregulation disorders. Moreover,these compounds have been reported for their efficacy in treatment of multi-drug resistant (MDR) tumors cells without mediated drug efflux, as well as their immunomodulatory activity and selectivity towards melanoma cell lines. This article is an overview of recent literature on lamellarins, encompassing their isolation, recent synthetic strategies for their total synthesis, the preparation of their analogs, studies on their mechanisms of action, and their structure-activity relationships (SAR).

A synthetic approach to palmerolides via Negishi cross coupling. The challenge of the C15-C16 bond formation

The esterification of fragment C1-C8 (2) with fragment C16-C23 (3) to give iodo derivative 4, followed by a Pd-catalysed coupling with a C9-C15 fragment (7 or 8), may provide a common precursor of most palmerolides. Ligands and reaction conditions were exhaustively examined to perform the C15-C16 bond formation via Negishi reaction. With simple models, pre-activated Pd-Xantphos and Pd-DPEphos complexes were the most efficient catalysts at RT. Zincation of the C9-C15 fragment (8) and cross coupling with 4 required 3 equiv of t-BuLi, 10 mol % of Pd-Xantphos and 60 °C.

Molecular Interactions of Prodiginines with the BH3 Domain of Anti-Apoptotic Bcl-2 Family Members.

Prodigiosin and obatoclax, members of the prodiginines family, are small molecules with anti-cancer properties that are currently under preclinical and clinical trials. The molecular target(s) of these agents, however, is an open question. Combining experimental and computational techniques we find that prodigiosin binds to the BH3 domain in some BCL-2 protein families, which play an important role in the apoptotic programmed cell death. In particular, our results indicate a large affinity of prodigiosin for MCL-1, an anti-apoptotic member of the BCL-2 family. In melanoma cells, we demonstrate that prodigiosin activates the mitochondrial apoptotic pathway by disrupting MCL-1/BAK complexes. Computer simulations with the PELE software allow the description of the induced fit process, obtaining a detailed atomic view of the molecular interactions. These results provide new data to understand the mechanism of action of these molecules, and assist in the development of more specific inhibitors of anti-apoptotic BCL-2 proteins.