13-Deoxytedanolide, a marine sponge-derived antitumor macrolide, binds to the 60S large ribosomal subunit

Golden Times for Allenes: Gold-Catalyzed Cycloisomerization of β-Hydroxyallenes to Dihydropyrans

The gold(I)-catalyzed 6-endo cycloisomerization of beta-hydroxyallenes provides a mild and efficient access to chiral functionalized dihydropyrans which were obtained at room temperature in good chemical yields with axis-to-center chirality transfer. The method was extended to the beta-aminoallene 12, which afforded tetrahydropyridine 13 in good yield as well.

Concise and stereoselective synthesis of the N7-C25 fragment of psymberin

[reaction: see text] The N7-C25 fragment of the potent and selective cytotoxic agent psymberin has been prepared through a short (12 linear steps, 15 total steps) and stereoselective sequence. Highlights of this route include a very rapid construction of the pentasubstituted arene, a substrate-controlled diastereoselective fragment coupling using a Mukaiyama aldol reaction, and an efficient entry into a key tetrahydropyranyl cyanide.

Myriaporone 3/4 structure--activity relationship studies define a pharmacophore targeting eukaryotic protein synthesis

Myriaporones are naturally occurring compounds which structurally resemble the southern hemisphere of the tedanolide family of macrolide antitumor agents. Despite the fact that myriaporone 3/4 represents only a portion of tedanolide, it nonetheless retains much of its biological activity. We show here that like tedanolide, myriaporone 3/4 inhibits protein synthesis and proliferation of mammalian cells with low nanomolar potencies but displays no prokaryotic growth inhibitory effect. Moreover, myriaporone 3/4 displays a very rapid, reversible and p21-independent activity to block S phase progression in mammalian cells. Structure-activity relationship studies revealed that the C18-C19 epoxide and the C14 hydroxymethyl group (tedanolide numbering) of myriaporone 3/4 are required for cell cycle inhibition. These constitute previously unidentified and/or novel pharmacophores for myriaporone 3/4. Our results show that the important biological activities associated with the structurally complex tedanolides are present and can be harnessed in the chemically much simpler myriaporones. This greatly increases the value of the latter as investigative tools for biochemical research as well as for development of potential therapeutics.

Induction of a ribotoxic stress response that stimulates stress-activated protein kinases by 13-deoxytedanolide, an antitumor marine macrolide

13-Deoxytedanolide is a structurally unique macrolide with strong antitumor activity isolated from a marine sponge. Recently, we showed that 13-deoxytedanolide bound to the large subunit of the yeast ribosome and inhibited polypeptide elongation in vitro, but the mechanism by which it exerts antitumor activity is still unknown. Here we show that 13-deoxytedanolide strongly induces plasminogen activator inhibitor 1 (PAI-1) promoter-derived gene expression. 13-Deoxytedanolide, unlike TGF-beta, did not cause apparent nuclear translocation of Smad2/3, but it relocalized the temperature-sensitive mutant of mouse p53 (p53Val153) from the cytoplasm to the nucleus at a nonpermissive temperature, suggesting that 13-deoxytedanolide inhibits protein synthesis. Indeed, the drug inhibited in vivo protein synthesis at low nanomolar concentrations and strongly activated stress-activated protein kinases such as p38 mitogen-activated protein kinase and Jun NH2-terminal protein kinase (JNK). Anisomycin, a well-known inducer of ribotoxic stress that activates both p38 and JNK, also activated PAI-1 gene expression, while other protein synthesis inhibitors that do not activate the kinases failed to do so. PAI-1 gene expression by 13-deoxytedanolide and anisomycin was blocked by SB202190, a specific inhibitor of p38, and SP600125, an inhibitor of both p38 and JNK. 13-Deoxytedanolide and anisomycin caused activation of apoptosis signal-regulating kinase 1, MKK3/MKK6, and SEK1/MKK4, the regulatory kinases upstream of p38 and JNK. These results suggest that 13-deoxytedanolide, like anisomycin, triggers a ribotoxic stress response that activates stress-activated protein kinase cascades, thereby inducing PAI-1 gene expression and apoptosis.

Tedanolide C: a potent new 18-membered-ring cytotoxic macrolide isolated from the Papua New Guinea marine sponge Ircinia sp

Cytotoxicity-guided fractionation of the crude methanol extract of a marine sponge, Ircinia sp., yielded tedanolide C (1), a new 18-membered macrolide. The structure was solved by interpreting NMR and MS data, and the relative stereochemistry was determined from a combination of homo- and heteronuclear coupling constants in conjunction with molecular modeling. Compound 1 exhibited potent cytotoxicity against HCT-116 cells in vitro. Cell cycle analysis showed that treatment of cells with compound 1 arrested cells in the S-phase.

Tedanolide C: a potent new 18-membered-ring cytotoxic macrolide isolated from the Papua New Guinea marine sponge Ircinia sp

Cytotoxicity-guided fractionation of the crude methanol extract of a marine sponge, Ircinia sp., yielded tedanolide C (1), a new 18-membered macrolide. The structure was solved by interpreting NMR and MS data, and the relative stereochemistry was determined from a combination of homo- and heteronuclear coupling constants in conjunction with molecular modeling. Compound 1 exhibited potent cytotoxicity against HCT-116 cells in vitro. Cell cycle analysis showed that treatment of cells with compound 1 arrested cells in the S-phase.

Synthetic studies of tedanolide, a marine macrolide displaying potent antitumor activity. Stereoselective synthesis of the C13-C23 segment

[structure: see text] A highly stereoselective synthesis of the C13-C23 segment of tedanolide (1), an 18-membered macrolide isolated from the Caribbean sponge Tedania ignis, displaying significant cytotoxicity against KB and PS tumor cell lines, is described which involves two stereoselective epoxidations of regioisomeric trisubstituted double bonds and a stereospecific S(N)2' methylation reaction of a trans-gamma,delta-epoxy-cis-alpha,beta-unsaturated ester as the key steps.

Marine natural products

This review covers the literature published in 2004 for marine natural products, with 693 citations (491 for the period January to December 2004) referring to compounds isolated from marine microorganisms and phytoplankton, green algae, brown algae, red algae, sponges, coelenterates, bryozoans, molluscs, tunicates and echinoderms. The emphasis is on new compounds (716 for 2004), together with their relevant biological activities, source organisms and country of origin. Biosynthetic studies (8), and syntheses (80), including those that lead to the revision of structures or stereochemistries, have been included.

Inhibition of protein synthesis and activation of stress-activated protein kinases by onnamide A and theopederin B, antitumor marine natural products

During the course of screening for the agents that activate transforming growth factor-beta (TGF-beta) signaling cascade, onnamide A and theopederin B, heterocyclic compounds related to mycalamides from a marine sponge, were found to induce plasminogen activator inhibitor-1 (PAI-1) promoter-derived gene expression in Mv1Lu cells. The maximum induction of the PAI-1 promoter by onnamide A and theopederin B was observed at the concentrations of 50 nM and 2 nM, respectively. These compounds strongly inhibited protein synthesis at the 50% inhibitory concentrations of 30 nM for onnamide A and 1.9 nM for theopederin B, and induced activation of p38 mitogen-activated protein kinase and c-Jun NH2-terminal protein kinase (JNK). Anisomycin, a well-known inducer of ribotoxic stress that inhibits protein synthesis and activates both p38 kinase and JNK, also activated PAI-1 gene expression. Furthermore, PAI-1 expression by onnamide A, theopederin B, and anisomycin was inhibited by SB202190 and SP600125, specific inhibitors of stress-activated protein kinases. Onnamide A and theopederin B were cytotoxic to a variety of cell lines and strongly induced apoptosis in HeLa cells within 24 h, which was accompanied by the sustained activation of p38 kinase and JNK. These results suggest that onnamide A and theopedirin B trigger a ribotoxic stress-like response, thereby inducing p38 kinase and JNK activation, the kinase-dependent PAI-1 gene expression, and apoptosis.