New bioactive cyclic peroxides from the Caribbean marine sponge Plakortis zyggompha

The new plakortide Q (1) has been isolated from the little studied marine sponge Plakortis zyggompha, together with the six new cyclic peroxide analogues 2-7 in their methyl ester forms 2a-7a. Their structure was fully elucidated through NMR and MS analyses and the relative stereochemistry of the 1,2-dioxane ring was established after interpretation of the coupling constant values and the NOESY data. The carboxylic acid function of these compounds was proved to be very reactive and methylation was found to take place during the purification process. The non-esterified peroxides exhibited more cytotoxic activity against human tumor cell lines than their corresponding methyl esters.     

Poecillastrin E,F, and G,cytotoxic chondropsin-type macrolides from a marine sponge Poecillastra sp.

Poecillastrin E (1), F (2), and G (3) were isolated from a marine sponge Poecillastra sp. as the cytotoxic constituents. Their planar structures were determined by analyzing the MS and NMR spectra. They are closely related to the known poecillastrin C (4). The absolute configuration of the β-hydroxyaspartic acid (OHAsp) residue was determined to be D-threo by Marfey's analysis of the hydrolysate. The mode of lactone ring formation of OHAsp residue in 1–3 was determined by selective reduction of the ester linkage followed by acid hydrolysis.     

Ircinamine B, bioactive alkaloid from marine sponge Dactylia sp.

Ircinamine B was isolated from the marine sponge Dactylia sp., which was collected at Cape Sada in Japan. Based on extensive spectral analysis, the structures of the isolated metabolites were established. This novel compound showed moderate activity against the murine leukemia cell line P388 (IC₅₀ 0.28 μg/mL).     

Solid phase total synthesis of callipeltin E isolated from marine sponge Latrunculia sp.

Solid phase total synthesis of callipeltin E (1), truncated linear peptide isolated from marine sponge, Latrunculia sp. was achieved. Our strategy based on traditional Fmoc-SPPS was in common use TFA-treatment final deprotection to reach callipeltin E (1) contained acid-sensitive βMeOTyr.     

Stellatolide H,a cytotoxic peptide lactone from a deep-sea sponge Discodermia sp.

Stellatolide H (1) was isolated from a deep-sea sponge Discodermia sp. as the cytotoxic constituent. The planar structure of 1 was elucidated on the basis of the NMR spectroscopic and mass spectrometric data. The absolute configurations of the constituent amino acid residues were determined by the Marfey’s method. Stellatolide H (1) is a peptide lactone of the callipeltin class with its N-terminus blocked by 3-hydroxy-6,8-dimethyldeca-(4Z,6E)-dienoic acid (Hdda).     

Exiguolide, a new macrolide from the marine sponge Geodia exigua

A new 20-membered macrolide designated exiguolide has been isolated from the marine sponge Geodia exigua, and its structure determined by interpretation of spectroscopic data. Exiguolide specifically inhibited fertilization of sea urchin (Hemicentrotus pulcherrimus) gametes but not embryogenesis of the fertilized egg.     

Axiplyns A-E, new sesquiterpene isothiocyanates from the marine sponge Axinyssa aplysinoides

Five new isothiocyanate sesquiterpenes, designated axiplyns A-E (1-5) have been isolated, together with two known isothiocyanate sesquiterpenes (6, 7), from the sponge Axinyssa aplysinoides collected at Misali Island, Tanzania. Axiplyns 4 and 5 embody a new indane sesquiterpene skeleton, and compounds 1, 2, and 5 contain unprecedented ring systems, namely a 6,8-dioxabicyclo[3.2.1]octane and a 2-oxabicyclo[2.2.1]heptane. Axiplyns A, B, and C are potent brine shrimp toxins with LD₅₀ values between 1.5 and 1.8 μg/mL.     

Synthesis of tokaramide A, a cysteine protease inhibitor from marine sponge Theonella aff. mirabilis

The first synthesis of tokaramide A (1) is described. Tokaramide A (1) was synthesized via the peptide with a side-chain unprotected arginine residue on Weinreb AM resin by reductive cleavage.     

Daminin, a bioactive pyrrole alkaloid from the Mediterranean sponge Axinella damicornis

The isolation and characterization of the known pyrrole alkaloid agelongine (6) and of the new natural product daminin (7), the bromine-free analogue of 6, from a specimen of the marine sponge Axinella damicornis is described. Compound 7 showed significant neuroprotective properties. Moreover, for the supply of sufficient material for future medicinal investigations, a short total synthesis of 7 was developed.     

Caldorin,a new polyketide from the marine cyanobacterium Caldora penicillata

A new polyketide with a cis-fused decalin ring scaffold, caldorin, was isolated from the marine cyanobacterium Caldora penicillata. The gross structure and relative configuration were elucidated by spectroscopic analyses. We also clarified that caldorin is a weak SOAT inhibitor and moderate osteoblast differentiation inhibitor. On the other hand, caldorin did not exhibit cytotoxicity against either HeLa or HL60 cells.     

Spironaamidine, a new spiroquinone-containing alkaloid from the marine sponge Leucetta microraphis

Spironaamidine (1), a unique spiroquinone-containing alkaloid, was isolated from the marine sponge, Leucetta microraphis, along with two known imidazole alkaloids, naamidine H (2) and (9E)-clathridine 9-N-(2-sulfoethyl)imine (3). Spironaamidine (1) showed antimicrobial activity against Bacillus cereus.     

New bromotyrosine alkaloids from the marine sponge Psammaplysilla purpurea

Seven new bromotyrosine alkaloids Purpurealidin A, B, C, D, F, G, H and the known compounds Purealidin Q, Purpurealidin E, 16-Debromoaplysamine-4 and Purpuramine I have been isolated from the marine sponge Psammaplysilla purpurea. Their structure was elucidated on the basis of detailed 1D, 2D NMR and MS spectroscopic data. Purpurealidin B, 16-Debromoaplysamine-4 and Purpuramine I exhibited in vitro antimicrobial activities against E. coli, S. aureus, and V. cholerae. In addition, Purpurealidin B and 16-Debromoaplysamine-4 were also active against Shigella flexineri and Salmonella typhi while Purealidin Q was bactericidal only against Salmonella typhi.     

Njaoamines G and H, two new cytotoxic polycyclic alkaloids and a tetrahydroquinolone from the marine sponge Neopetrosia sp.

Two new polycyclic alkaloids, njaoamines G (1) and H (2) and 1,2,3,4-tetrahydroquinolin-4-one (3) have been isolated from the sponge Neopetrosia sp. collected at Pemba Island, Tanzania. Compounds 1 and 2 are close in structure to njaoamines A-F. Compound 3, known synthetically, is a new natural compound. The structures and relative stereochemistries of compounds 1 and 2 were elucidated on the basis of spectroscopic data. Njaoamines G and H are potent brine shrimp toxins with LD₅₀ values of 0.17 μg/mL and 0.08 μg/mL for 1 and 2, respectively.     

Ishigadine A,a new canthin-6-one alkaloid from an Okinawan marine sponge Hyrtios sp.

A new indole alkaloid with the canthin-6-one skeleton, ishigadine A, has been isolated from an Okinawan marine sponge Hyrtios sp. The structure of ishigadine A was elucidated on the basis of spectroscopic analyses. Ishigadine A is a new canthin-6-one alkaloid possessing a hydroxy group, a 1,3-dimethyl-4-methylthioimidazolium, and a 1-propylguanidine. Ishigadine A is the third canthin-6-one alkaloid from sponges. Ishigadine A might be generated from l-arginine, l-histidine, and l-tryptophan. Ishigadine A exhibited moderate cytotoxicity against L1210 murine leukemia cells.     

Synthesis of (±)-halipanicine, a marine sesquiterpene isothiocyanate isolated from an Okinawan marine sponge Halichondria panicea

(±)-Halipanicine, 4-isothiocyanato-1-cadinene, isolated from an Okinawan marine sponge Halichondria panicea was synthesized from (±)-cryptone in 21 steps in 7.7% total yield. The regio- and stereospecific synthesis esablished the relative stereochemistry of halipanicine.     

Njaoamine I,a cytotoxic polycyclic alkaloid from the Haplosclerida sponge Haliclona (Reniera) sp.

A new cytotoxic polycyclic alkaloid containing a quinoline moiety, njaoamine I (1) has been isolated from the methanol extract of the sponge Haliclona (Reniera) sp. collected at Okuza Island, Tanzania. The structure of compound 1 was determined by 1D and 2D NMR and HRMS data analysis. Its relative configuration was elucidated by a NOESY experiment and confirmed by comparison of its NMR spectral data to those of njaoamines A–H. Moreover, njaoamine G (2) was also detected by LC/MS analysis of the methanol extract. Njaoamine I (1) displays cytotoxic activity against a panel of three human tumor cell lines in the micromolar range.     

Dihydrohymenialdisines, new pyrrole-2-aminoimidazole alkaloids from the marine sponge Cymbastela cantharella

In our investigation of bioactive marine natural products, we revisited an ethanolic extract of the New Caledonian sponge Cymbastela cantharella. Four new natural compounds (3-6) were isolated and their structural determinations as dihydrohymenialdisine derivatives were achieved by spectral data analysis and chemical conversion. These products did not show any activity in the Polo Like kinase bioassay, demonstrating thus the importance of the unique structure of hymenialdisine, known as an improved kinase inhibitor.     

Myrmekiosides a and b, novel mono-o-alkyl-diglycosylglycerols reversing tumor cell morphology of ras-transformed cells from a marine sponge of myrmekioderma sp

Novel mono-O-alkyl-diglycosylglycerols named myrmekiosides A (1) and B (2) were isolated from a marine sponge of Myrmekioderma sp. and their absolute stereostructures were elucidated on the basis of chemical and physicochemical evidence. Myrmekiosides A (1) and B (2) reversed the phenotype of melanoma H-ras transformed NIH3T3 cells at 5 μg/ml.     

Aplysiopsenes: an additional example of marine polyketides with a mixed acetate/propionate pathway

First chemical study of the Hermaeidae sacoglossan Aplysiopsis formosa from Azores led to aplysiopsenes, α-pyrone polyketides with a mixed acetate/propionate structural pathway.     

Brominated polyunsaturated lipids and their stereochemistry from the Chinese marine sponge Xestospongia testudinaria

Chemical examination of the Chinese marine sponge Xestospongia testudinaria led to the isolation of 39 new brominated polyunsaturated compounds, which were designated with the trivial names xestospongienes A-Z and Z₁-Z₁₃. The structures of these compounds were elucidated by analyzing extensive spectroscopic (IR, MS, 1D, and 2D NMR) data and the results from CD spectral assignment, chemical conversion, and Mosher reaction.