The rhodophytin and chondriol natural products; structures of several new acetylenes from laurencia, and a reassignment of structure for cis-rhodophytin

The structures of five new halogenated vinyl acetylenes are described which are natural products from various species of the red seaweed Laurencia. The structure of epoxyrhodophytin (1) was determined by spectral, chemical, and X-ray diffraction analyses. The structures of trans-rhodophytin (5) and trans-chondriol (8) are based on chemical and spectral comparisons with the previously reported compounds cis-rhodophytin (4) and cis-chondriol (7). The structures of cis-chondrin (14) and trans-chondrin (15) were secured by synthesis from cis- and trans-chondriol, respectively. The reactivity of these enol-ethers to various conditions of catalytic hydrogenation has been examined in detail. Hydrogenation yields an unexpected and facile incorporation of oxygen into the reaction products. Based upon these studies, and upon combustion analysis, the structure of rhodophytin has been revised as the vinyl ether rather than the vinyl peroxide originally proposed.     

Isocaespitol,a new halogenated sesquiterpene from Laurencia caespitosa

The halogenated sesquiterpene isocaespitol (1) has been isolated from the marine alga Laurencia caespitosa Lamx and its structure determined by X-ray crystallography.     

Chemical studies of marine invertebrates—XLIII: Novel sesquiterpenes from clavularia inflata and clavularia koellikeri (Coelenterata,Octocorallia,Stolonifera)

Two novel sesquiterpenes, 12-acetoxycyclosinularane (1) and 12-acetoxysinularene(2),have been isolated from Clavularia inftata. Their structures have been determined by X-ray diffraction analysis and chemical correlation respectively. Moreover, the new aromadendrane sesquiterpene(1R^*, 1aS^*, 4R^*, 7R^*, 7aS^*, 7bS^*, 5Z)-4,4a,7-trihydroxyaromadendr-5-en-8-oic acid methyl ester (19) has been isolated from the related species C. koellikeri. Its structure has been established by X-ray diffraction analysis. These compounds are the first sesquiterpenes isolated from Octocorallia of the order Stolonifera.     

Non-terpenoid C-15 metabolites from the red seaweed Laurencia pinnatifida

The structures of absolute configurations of the halogenated vinyl acetylenes which are natural products from the red alga Laurencia pinnatifica (Gmal. Lamour) are described. The structure of trans- pinnatifidenyne 2 was determined by spectral, chemical and X-ray diffraction analyses. The structure of cis-pinnatifidenyne 1 is based on spectral comparison and chemical interconversion with the trans-isomer 2. The structure of the acyclic trienyne 8 was secured as: (6R,7R)-3-cis, 9-cis,12-cis,6-acetoxy,7-chloropentadeca-3,9,12-trien-1-yne by synthesis from cis-pinnatifidenyne 1. The reactivity of these compounds to various conditions of catalytic hydrogenation has been examined in detail.     

Itomanindoles A and B. Methylsulfinylindoles from Laurencia Brongniartii

Optically active 2- and 3-methylsulfinylindoles 2 and 3 have been isolated from the red alga Laurencia brongniartii. The structure of 2, and hence 3 by comparison, was determined by X-ray and revealed a pair of hydrogen-bonded molecules possessing a center of inversion.     

The structure of spirolaurenone,a halogenated sesquiterpenoid from the red alga laurencia glandulifera kützing

The structure of spirolaurenone (1), a halogenated metabolite isolated from the red alga Laurencia glandulifera Kützing, was determined on the basis of the chemical and spectroscopic evidence. The absolute configuration of spirolaurenone (1) was established as shown in formula 1 by the chemical correlation with glanduliferol (18), a halo-chamigrene derivative isolated from the same alga.     

A new ent-norabietant diterpenoid from roots of Euphorbia lathyris L.

A new highly oxidized ent-norabietane diterpenoid named lathyrisol A (1) was isolated from roots of Euphorbia lathyris L. The structure and absolute configuration of 1 were elucidated on the basis of data obtained by HRESIMS, NMR, and the Cu-Kα radiation X-ray diffraction analysis. This compound is the first example of naturally occurring norabietane diterpenoid with an exocyclic olefin at the C-4 position.     

Helicenes: an intramolecular insertion reaction involving the helicene skeleton

1-Formyl[6]helicene tosylhydrazone (1a) heated in benzene solution in the presence of NaH gave a carbene insertion product, whose structure (2) was determined by ¹H and ¹³C-NMR spectroscopy and fully confirmed by an X-ray diffraction study carried out by A. Van Meerssche et al. The resolution of the new hydrocarbon (2) has been achieved by hplc, using a silica-gel column impregnated with (?)TAPA.     

Structure and absolute configuration of penicilliumine,a new alkaloid from Penicillium commune 366606

Penicilliumine (1), a new structure was isolated from the fermentation Penicillium commune 366606, a marine-derived fungus isolated from the sea water collected at Qingdao, China. HPLC chiral separation of 1 afforded two enantiomers (−)-penicilliumine and (+)-penicilliumine, respectively. The structure of 1 was established by comprehensive spectroscopic data, and single-crystal X-ray diffraction. The absolute configuration of enantiomers was determined by quantum mechanical computation of electronic circular dichroism (ECD).     

Streptopyrazinones A−D,rare metabolites from marine-derived Streptomyces sp. ZZ446

Secondary metabolites from marine-associated actinomycetes are important source for the discovery of novel bioactive compounds. In this study, an actinomycete Streptomyces sp. ZZ446 was isolated from coastal soils and different media were used to culture this isolated marine actinomycete. It has been found that this actinomycete in the liquid medium of 2216?E with sea salt produced five new compounds of streptopyrazinones A?D (1–4) and N-acetyl-l-isoleucine-l-leucinamide (5) as well as six known diketopiperazines (6–11) and one alkaloid (12). Structures of the new compounds were determined by extensive NMR analyses, HRESIMS data, electronic circular dichroism (ECD) calculation, chemical degradation, Marfey's method, and X-ray diffraction analysis. This type of streptopyrazinones A?D (1–4) is rarely found in the natural resources. New compounds 1–5 showed activity in inhibiting the growth of Candida albicans and methicillin-resistant Staphylococcus aureus.     

(+)- and (−)-Eurotone A: A pair of enantiomeric polyketide dimers from a marine-derived fungus Eurotium sp. SCSIO F452

(±)-Eurotone A [(±)-1], a pair of new enantiomeric polyketide dimers, as well as six known biogenetically related polyketides (2–7) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by comprehensive spectroscopic methods, X-ray diffraction and quantum chemical calculations. Compound 1 represented the first pair of spirodihydrobenzanthracene enantiomers isolated from marine fungi with their absolute configurations assigned. A plausible biosynthetic pathway involving a key acid-mediated dimerization was proposed for 1. The antioxidative activities of the new enantiomers were evaluated.     

Sesquiterpene metabolites from laurencia filiformis

The major lipid components of Laurencia filiformis have been shown to be aplysistatin 1 and 6β-hydroxyaplysistatin 2. The structure and absolute configuration of these sesquiterpenes has been confirmed by X-ray diffraction methods. An interesting thermal rearrangement of2 is described.     

Mersiphyllines A and B from Kopsia. Determination of relative configuration at a quaternary center via formation of an alkaloid-borane complex

Two new pentacyclic alkaloids, mersiphyllines A (1) and B (2), belonging to the novel mersinine group, and incorporating carboxylic acid functionalities on a quaternary center, were isolated from Kopsia singapurensis. The structures were determined by spectroscopic analysis. Determination of the relative configuration at the quaternary center bearing the acid function was facilitated by the formation of an alkaloid-borane complex. The structure of 1 was also confirmed by X-ray diffraction analysis.     

Dolastanes from the brown alga Dilophus spiralis: absolute stereochemistry and evaluation of cytotoxicity

Five new dolastanes (1-5) were isolated from the brown alga Dilophus spiralis. The structural elucidation of the isolated compounds and the assignment of relative stereochemistry were based on analyses of their spectroscopic data. The structure proposed for 1 was confirmed by single crystal X-ray diffraction analysis, whereas its absolute stereochemistry was determined using the modified Mosher's method. The cytotoxicity of 1-4 was evaluated against seven cell lines.     

The alkaloids from the fruits of the plant Daphniphyllaceae

Six alkaloids have been isolated from the fruits of the plant Daphniphyllaceae. Two of them are new alkaloids, namely methyl homodaphniphyllate (1) and daphnilactone-B (2). The structure of the former was deduced by chemical transformation from daphniphylline (3). The structure of daphnilactone-B was estimated by the exhaustive spectral analysis as well as by chemical evidences, and finally determined by an X-ray crystallographic analysis of the free base.     

New cytotoxic sesquiterpenes from the red algae Laurencia obtusa and Laurencia microcladia

Three new sesquiterpenes (1-3), along with five known (5-9), were isolated from the organic extract of the red alga Laurencia obtusa, collected from the coastal rocks of Serifos in the Aegean Sea. A new dimeric sesquiterpene of the cyclolaurane-type (4) along with four previously reported (7, 10-12) metabolites, were isolated from the extract of Laurencia microcladia, collected at Chios island in the North Aegean Sea. The structures and the relative stereochemistry of the compounds are proposed on the basis of their spectral data. The cytotoxicity of the isolated metabolites was evaluated against several cell lines including human tumor cell lines.     

Humulene derivatives from Saharian Asteriscus graveolens

Three new sesquiterpene-humulenes, (?)- asteriscunolides I (1), J (2) and (?)-(2Z,6E,9Z)-8-oxo-1α-acetoxy-2,6,9-humulatrien-12-oic acid (3) were isolated from the leaves-flowers of the Saharan medicinal plant Asteriscus graveolens along with six known compounds. The structures of the compounds were determined on the basis of spectroscopic mono and bidimensional NMR, mass spectrometry and by single-crystal X-ray diffraction. Compounds 1–3 were evaluated for cytotoxic assay, no significant activity was detected.     

The coraxeniolides,constituents of pink coral, corallium sp

From a deep-sea (?350m) gorgonian, Corallium sp., we have isolated five diterpenes, which are structurally related to the xenicins, previously known from soft corals and brown algae. The structure of the principal constituent, coraxeniolide-A (1) was determined by X-ray diffraction studies. Spectral analysis and chemical correlations elucidated the structures of coraxeniolides B(3), C(7), C'(10), and of corabohcin (13).     

Synthesis, structure, and absorption spectra of complex neptunium(V) chromate with the guanidinium cation, [C(NH2)3]3[NpO2(CrO4)2] · (H2O)

A new complex of Np(V) with the chromate ion and an organic outer-sphere guanidinium cation is isolated from an aqueous solution. Its composition and structure are determined by X-ray diffraction analysis. The structure of [C(NH₂)₃]₃[NpO₂(CrO₄)₂](H₂O) (I) is based on anionic chains [CpO₂(CrO₄)₂][ _n ^3nt- between which guanidinium cations and crystallization water molecules are localized. Coordination polyhedra of the Np atoms (pentagonal bipyramids) in the anionic chains are joined in pairs through common equatorial edges. Singularities of the electronic and IR absorption spectra of compound I are discussed.     

Phomactin H, a novel diterpene from an unidentified marine-derived fungus

Phomactin H (1), a diterpene has been isolated from cultures of an unidentified marine-derived fungus. The structure and relative stereochemistry of phomactin H (1) was determined by X-ray diffraction analysis. Phomactin H (1), having an oxepane moiety, is a new phomactin with a novel skeleton.