Leucascandrolide A,a New Type of Macrolide: The first powerfully bioactive metabolite of calcareous sponges (Leucascandra caveolata,a new genus from the coral sea)

Leucascandrolide A ((+)- 1 ), a doubly O-bridged 18-membered macrolide of a new type, i.e., showing little C₁-branching vs. extensive 1,3-dioxygenation and a peculiar side chain, was isolated from a calcareous sponge of a new genus, Leucascandra caveolata BOROJEVIC and KLAUTAU from the Coral Sea. Transesterification of (+)- 1 gave the methyl ester 3 , derived from the side chain, and the 5-hydroxy derivative (+)- 2 , derived from the macrolide portion and with the natural configuration at C(5) (axial). Mosher's MTPA esters 4 and 5 obtained from (+)- 2 showed scattered Δδ = (δ(S) ? δ(R)) data. However, inversion of the configuration at C(5) led, via ketone (+)- 6 , to the less encumbered 5-equatorial hydroxy derivative (+)- 7 , whose MTPA esters 8 and 9 gave consistent Δδ data, allowing the assignment of the absolute configuration of (+)- 7 , and hence of (+)- 1 . The structural novelty of (+)- 1 and its powerful antifungal and cytotoxic activities are likely to renew interest in calcareous sponges, previously limited to scarcely biologically active 2-aminoimidazoles.     

Sphinxolide,a 26-Membered Antitumoral Macrolide Isolated from an Unidentified Pacific Nudibranch

It is shown that an unidentified nudibranch of Hawaiian waters contains a 26-membered macrolide, sphinxolide ((?)- 1 ) with potent activity against the KB cell line. The structure of sphinxolide, a 2:1 mixture of (E/Z)-isomers at the formamide moiety, is established to be (–)- 1 on the basis of extensive NMR and FAB-MS analysis, in combination with data for the products of mono- (→(?)- 2 ) and diacetylation (→(+)-3).     

From Inactive Nortopsentin D,a Novel Bis(indole) Alkaloid Isolated from the Axinellid Sponge Dragmacidon sp. from Deep Waters South of New Caledonia,to a Strongly Cytotoxic Derivative

Nortopsentin D ( 5 ), a bis(indole) alkaloid unique for bearing a 2-amino-methylimidazole appendage at the central 1H-imidazol-5(4H)-one nucleus, was isolated in abundance, besides the putative biogenetic precursor 6 of its appendage, from the deep-water axinellid sponge Dragmacidon sp. Structural elucidation of 5 by NMR and MS methods heavily relied on its N-methyl derivatives 8–11 . Unusually for topsentin-type structures, natural 5 and semisynthetic methyl derivatives 8 and 10 proved inactive on KB tumoural cells, while introduction of the last three methyl groups, amazingly led to highly cytotoxic 11 .     

Relative Configuration of JBIR-129, a Cytotoxic 34-Membered Glycosidic Polyol Macrolide from Streptomyces sp. RK74

JBIR-129 was isolated as the potent cytotoxic compound, which consists of the 34-membered polyol macrolide skeleton with five sugar moieties. The relative configuration of the aglycone moiety (C7-C27 and C33-C39) was established by the J-based configuration analysis using vicinal (1)H-(1)H (from (1)H NMR and PS-DQF-COSY spectra) and long-range (1)H-(13)C coupling constants (from sge-HETLOC and several J-resolved HMBC spectra) with steric information obtained from ROESY.     

Densazalin,a New Cytotoxic Diazatricyclic Alkaloid from the Marine Sponge Haliclona densaspicula

Densazalin, a polycyclic alkaloid, was isolated from the marine sponge Haliclona densaspicula collected in Korea. The complete structure of the compound was determined by spectroscopic methods, including 1D and 2D nuclear magnetic resonance techniques, high-resolution mass spectrometry, and comparison of the calculated and measured electronic circular dichroism spectra. Densazalin possesses a unique 5,11-diazatricyclo[7.3.1.0^2,7]tridecan-2,4,6-triene moiety, which is connected by two linear carbon chains. This compound was derived from the biogenetic precursor bis-1,3-dialkylpyridnium. Densazalin exhibited cytotoxic activity on two human tumor cell lines (AGS and HepG2) in the Cell Counting Kit-8 (CCK-8) bioassay, with IC₅₀ values ranging from 15.5 to 18.4 μM.     

Novel Naamidine-Type Alkaloids and Mixed-Ligand Zinc(II) Complexes from a Calcareous Sponge,Leucetta sp., of the Coral Sea

As compounds from a calcareous sponge, Leucetta sp., of the Coral Sea, we isolated a series of novel naamidine-type alkaloids, 6 – 10 , which are oxidized at a single benzylic position. We also report on the first marine, mixed-ligand metal complex 5 and on the first natural metal complexes 3 and 4 derived from classical naamidines, i.e., 1 and 2 . The latter are also present in free form in the sponge.     

New Sesquiterpenes from a Taiwanese Marine Sponge of the Genus Parahigginsia

An undescribed Taiwanese marine sponge of the genus Parahigginsia yielded two new sesquiterpene hydrocarbons-parahigginine ( 1 ) and parahigginone ( 2 ). The structures of the new compounds were established on the basis of NMR spectroscopic and mass spectrometric data. Compounds 1 and 2 exhibited moderate cytotoxicity against murine P-388 and human KB-16, A-549, and HT-29 tumor cells.     

Phyllofenone A, a New Scalarane Sesterterpene from the Sponge Phyllospongia Foliascens(Pallas)

The present paper covers the structure of a new sesterterpene, phyllofenone A(1) , isolated from the South China Sea sponge Phyllospongia foliascens. Phyllofenone A is a member of the scalarane class of sesterterpenes with a (C-20, C-24)-bishomo-(C-25)-nortetra-cyclic skeleton. The structure charcterization was based on one- and two-dimensional NMR and mass spectroscopy with the assistance of molecular modeling. Phyllofenone A shows weak antifungal activity against Candida pseudotropicalis.     

Ent-untenospongin A, a New C21 Furanoterpene from the Indian Marine Sponge Hippospongia sp

Many marine sponges of the family Spongiidae, in particular, the genus HiPPospongiafrequently afford terpenoids containing ZI carbons and displaying two Asubstitutedfuran moieties at the end of the molecule2. These unusual compounds are probablyderived from higher terpenoids from a biogenetic point of view. During our studies onbioactive substances from marine organisms, we investigated the extracts of the indiansponge HiPPospongia sp. and isolated a new C,, furanoterpene, named enluntenos…     

Adriadysiolide,the First Monoterpenoid Isolated from a Marine Sponge

Spectra and chemical transformations allow to establish the gross structure 6,7-epoxy-4,7-dimethyl-l-oxa-spiro[4.4]non-3-en-2-one for adriadysiolide ( 1 ), the first monoterpenoid isolated from a marine sponge, a Dysidea sp. of the Adriatic Sea. Its configuration 5R*, 6S*, 7S* as given in 1a is derived from diastereoselective total syntheses of both 1a and its diastereoisomer 1b via stereochemically predictable peracid epoxidations of olefinic precursors. Thus, OH assistance in allylic alcohol 8 leads to oxirane 13 which is subjected to methyl cuprate conjugate addition to give epiadriadysiolide ( 1b ), whilst electronic deactivation by a neighboring heterocyclic O-atom in intermediate 5 , derived from 8 mainly leads to adriadysiolide ( 1a ). Comparative ¹H-NMR shift-reagent effects with 1a and 1b , evaluated with the aid of molecular-mechanics calculations, support these conclusions.     

Isolation,Structure Determination and Synthesis of New Acetylenic Steroids from the Sponge Calyx nicaaensis

Two acetylenic steroids, cholest-5-en-23-yn-3β-ol ( 5 ) and 26,27-dinorcholest-5-en-23-yn-3β-ol ( 3 ), and another unsaturated steroidalcohol, stigmasta-5,23-dien-3β-ol ( 7 ), were isolated from the sponge Calyx nicaaensis. The structures of these two acetylenic steroids were established by synthesis. Several attempts to synthesize the marine steroids alcohol calysterol ( 1 ), with a cyclopropene-containing side chain, starting from cholest-5-en-23-yn-3β-ol are also recorded. Addition of ethyl-diazo-acetate to the triple bond was performed, but the reduction to the methyl derivative yielded decomposition products.     

Hemislin B Glucoside,a New Lignan from Hemistepta Lyrata

From the ethanolic extract of the whole plant of Hemistepta lyrate Bunge., a new lignan, named hemislin B glucoside,has been isolated and identified as α-(trans-3-methoxy-4-O-β-D-glucopyranosylbenzylidene)-β-(3,4-dimethoxybenzyl)-γ-butyrolactone. Its structure has been established on the basis of UV,IR,FABMS,^1H-NMR,^13C-NMR,HMQC and HMBC spectral analysis.