Intricarene, an unprecedented trispiropentacyclic diterpene from the Caribbean Sea plume Pseudopterogorgia kallos

[structure: see text] A novel trispiropentacyclic diterpene, intricarene (1), was isolated from the hexane extract of the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly entangled structure was established by interpretation of NMR, IR, UV, and HREIMS data and subsequently confirmed by X-ray diffraction analysis. The unprecedented carbon skeleton of 1 constitutes a new addition to the already impressive architectural diversity of the diterpene class of marine secondary metabolites.     

Isolation and structure of providencin: a highly oxygenated diterpene possessing a unique bicyclo[12.2.0]hexadecane ring system from the sea plume Pseudopterogorgia kallos

[structure: see text] Providencin (1) is a naturally occurring cytotoxin isolated from the Caribbean gorgonian octocoral Pseudopterogorgia kallos. Its highly oxygenated hexacyclic structure is based on a previously undescribed bicyclo[12.2.0]hexadecane ring system and was established through spectroscopic analysis and X-ray crystallographic analysis. Providencin (1) was shown to exhibit modest anticancer activity against human breast (MCF7), lung (NCI-H460), and CNS (SF-268) cancer cell lines.     

Holophyllin A,a rearranged abietane-type diterpenoid from the trunk of Abies holophylla

Holophyllin A (1), a novel rearranged abietane-type diterpenoid was isolated, together with a new diterpene glycoside, holophyllin B (2), from the trunk of Abies holophylla. The structures of 1 and 2 were established by extensive spectroscopic analyses and their absolute configurations were determined by ECD calculation. All the isolates were tested for their inhibitory effects on NO production in LPS-activated murine microglial cells.     

Salvileucalin B, a novel diterpenoid with an unprecedented rearranged neoclerodane skeleton from Salvia leucantha Cav

Salvileucalin B (2), having an unprecedented rearranged neoclerodane skeleton, was isolated from the aerial parts of Salvia leucantha Cav. (Labiatae) along with salvileucalin A (1). The absolute structures were elucidated by spectroscopic analysis, X-ray crystallographic analysis, and vibrational circular dichroism. Compound 2 represents a novel neoclerodane, characterized by a tricyclo[3.2.1.0 (2,7)]octane substructure incorporating the exocyclic C-20 methylene of 1. This molecule exerted cytotoxic activity against A549 and HT-29 cells with IC50 values of 5.23 and 1.88 microg/mL, respectively.     

A crotofolane-type diterpenoid and a rearranged nor-crotofolane-type diterpenoid with a new skeleton from the stems of Croton cascarilloides

From the stems of Croton cascarilloides collected in the Okinawa Islands, a structurally rare crotofolane-type diterpenoid (1) and a rearranged nor-crotofalane, a new skeletal diterpenoid (2) were isolated. The structures were determined by X-ray crystallographic analyses, establishing their absolute stereostructures for the first time. Compound 2 was probably biosynthesized from 1 through several steps, such as decarboxylation, oxidation, C-C bond migration.     

The cumbiasins, structurally novel diterpenes possessing intricate carbocyclic skeletons from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer)

From the hexane extract of the West Indian gorgonian Pseudopterogorgia elisabethae, two diterpenes, cumbiasins A (1) and B (2), having a novel tetracyclic carbon skeleton named cumbiane, have been isolated. In addition, we have isolated cumbiasin C (3), a ring cleavage product of cumbiasin B that possesses an unusual carbocyclic framework named seco-cumbiane. The structures and relative configurations of metabolites 1-3 were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS). The carbocyclic skeletons of the cumbiasins are unprecedented and represent new classes of C20 rearranged diterpenes. Cumbiasins A and B display mild in vitro anti-tuberculosis activity.     

Isolation, structure elucidation, and synthesis of bisgersolanolide, a novel heptacyclic bis-diterpenoid from the gorgonian octocoral Pseudopterogorgia bipinnata

[formula: see text] A chemical study of the hexane extracts of the Caribbean gorgonian Pseudopterogorgia bipinnata (Verrill) collected in San Andrés Island, Colombia, has led to the isolation of an unprecedented heptacyclic C40 bis-diterpenoid, bisgersolanolide (1). The structure of this novel secondary metabolite, which was established by spectroscopic studies that included 2D NMR correlation methods, IR, UV, and accurate mass measurements, was confirmed by synthesis.     

Novel terpenoids from the West Indian sea whip Pseudopterogorgia elisabethae (Bayer). Elisapterosins A and B: rearranged diterpenes possessing an unprecedented cagelike framework

Four diterpenes and a nor-diterpenoid, all of which possess unusual carbocyclic skeletons, were isolated from the hexane solubles of the West Indian gorgonian Pseudopterogorgia elisabethae. The structures and relative configurations of novel metabolites elisabethin D (2), elisabethin D acetate (3), 3-epi-elisabanolide (5), elisapterosin A (6), and elisapterosin B (7) were elucidated by interpretation of overall spectral data, which included 2D NMR correlation methods, IR, UV, and accurate mass measurements (HREI-MS and HRFAB-MS), chemical reactions, and X-ray diffraction analyses. The tetracyclic carbon skeleton of the elisapterosins is undescribed and constitutes a new class of C(20) rearranged diterpenes. Elisapterosin B displays strong in vitro anti-tuberculosis activity.     

Structure of salvioccidentalin, a diterpenoid with a rearranged neo-clerodane skeleton from Salvia occidentalis

From the aerial parts of Salvia occidentalis (Labiatae) a new diterpenoid with a rearranged neo-clerodane skeleton was isolated. This new compound was named salvioccidentalin and its structure was established by spectroscopic means. A probable biogenetic relationship with salvigenolide from S. fulgens and salvileucalin A and spiroleucantholide from Salvia leucantha is proposed.     

Structure of salvigenolide,a novel diterpenoid with a rearranged neo-clerodane skeleton from salviafulgens

From the aerial parts of Salvia fulgens Cav. (Labiatae) a new diterpenoid with a rearranged neo-clerodane skeleton was isolated. This novel compound named salvigenolide, showed a six-seven A/B ring system with a trans fussion. A probable biogenetic route is proposed. Its structure and relative stereochemistry as in $\text{1}$, were established by spectroscopic means and X-ray diffraction analysis.     

Gersolide,a diterpenoid with a new rearranged carbon skeleton from the soft coral Gersemia rubiformis

The structure of gersolide (4), a diterpenoid isolated from extracts of the soft coral Gersemia rubiformis, has been solved via single crystal x-ray diffraction analysis.     

Isolation,Structural Analysis and Biological Activity Assays of Biselisabethoxanes A and B: Two Dissymmetric Bis-Diterpenes from the Southwestern Caribbean Sea Gorgonian Coral Pseudopterogorgia elisabethae

Two novel dissymmetric diterpenoids, biselisabethoxanes A and B (1 and 2), were isolated from the hexane extracts of the gorgonian coral Pseudopterogorgia elisabethae. Biselisabethoxane A (1) represents the first example of a marine-derived C₄₀ dimer made of two distinct diterpene fragments, whereas biselisabethoxane B (2) is a fused heterodimer stemming from coupling of two amphilectane-based fragments. The structures of 1 and 2 were elucidated based on 1D and 2D NMR spectral data analysis. The molecular structure of 1 was subsequently confirmed by X-ray crystallographic analysis. When evaluated for their inhibitory effects in a series of well-established biological activity assays the isolated compounds were shown to moderately inhibit the growth of Mycobacterium tuberculosis.     

Total synthesis of (+/-)-13-methoxy-15-oxozoapatlin, a rearranged kaurane diterpenoid

A 21-step linear synthesis of the structurally novel and biologically intriguing diterpenoid (+/-)-13-methoxy-15-oxozoapatlin (6) is described. Of particular note in this work is the development of a new method for the construction of the functionalized bicyclo[3.2.1]octane unit present in the target substance.     

Sinutriangulin A, a novel diterpenoid from the soft coral Sinularia triangula

A novel compound, named sinutriangulin A (1), was isolated from the soft coral Sinularia triangula. The compound possesses a new carbon skeleton that is derived from the cubitane skeleton. The structure was determined by extensive spectroscopic analyses. In addition, compound 1 exhibited weak cytotoxicity toward human tumor cell lines CCRF-CEM and DLD-1.     

Rhizophorin A, a novel secolabdane diterpenoid from the Indian mangrove plant Rhizophora mucronata

The ethyl acetate extract of Rhizophora mucronata furnished rhizophorin A, a novel secolabdane diterpenoid, (6R,11S,13S)-6,11,13-trihydroxy-2,3-seco-14-labden-2,8-olide-3-oic acid (1).     

Isolation and characterization of a new benzofuran from the fungus Alternaria sp. (HS-3) associated with a sea cucumber

A new compound, 4-acetyl-5-hydroxy-3, 6, 7-trimethylbenzofuran-2(3H)-one (1), together with two known compounds, 2-carboxy-3-(2-hydroxypropanyl) phenol (2) and 5-methyl- 6-hydroxy-8-methyoxy-3-methylisochroman (3) were isolated from the fungus Alternaria sp. (HS-3) associated with a sea cucumber from the Yellow Sea in China. Their structures were elucidated by spectral methods.     

Chamobtusin A, a novel skeleton diterpenoid alkaloid from Chamaecyparis obtusa cv. tetragon

The novel diterpenoid alkaloid chamobtusin A (1) was isolated from the branches and leaves of Chamaecyparis obtusa cv. tetragon. Its structure and relative stereochemistry were mainly determined by MS, 2D NMR, and X-ray methods. The methanol extracts, total alkaloids of C. obtusa cv. tetragon, and chamobtusin A were tested for their cytotoxicities against A549 and K562 human tumor cell lines.