Two New Seco-Labdane Diterpenoids from the Leaves of Callicarpa nudiflora

Two new seco-labdane diterpenoids, nudiflopene N (1) and nudiflopene O (2), and four known compounds were isolated from the leaves of Callicarpa nudiflora. The structures of the new compounds were established by 1D-, 2D-NMR, and HR-ESI-MS spectral analyses. Compounds 1–3 showed inhibitory activities on lipopolysaccharide-induced nitric oxide (NO) production in RAW264.7 cells, and new compounds 1–2 exhibited more potent inhibitory activity than compound 3. The cytotoxicity of compounds 1–3 against human hepatocellular carcinoma HepG2 cells and human gastric carcinoma SGC-7901 cells were evaluated, while all of them exhibited no cytotoxicity.     

Total Synthesis of Liangshanone

The first total synthesis of liangshanone, a hexacyclic ent-kaurane diterpenoid alkaloid, has been completed. Its intricate cagelike framework was assembled through several key transformations, including an oxidative dearomatization/Diels–Alder (OD/DA) cycloaddition sequence, a tandem alkene cleavage/Mannich cyclization, a Robinson-type annulation, and an intramolecular aldol reaction. Notably, an organocatalytic enantioselective α-hydroxymethylation process allowed the preparation of an enantiomerically enriched tricyclic intermediate that should enable asymmetric access to the target natural product.     

Vilsmeier—Haack reaction of methyl lambertianate and non-sensitized photocyclization of the resulting product

Vilsmeier—Haack formylation of methyl lambertianate results in its 16-formyl derivative as the predominant product, which readily enters the intramolecular reaction of photochemical [2+2]-cycloaddition in the absence of a sensitizer.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2514–2517, December, 1995.     

A Novel Atisane Diterpenoid from Spiraea japonica var. acuta

A novel ent‐atisane lactone, spiramilactone E ( 1 ), was isolated from Spiraea japonica var. acuta Yu . Its structure was elucidated by extensive spectroscopic analyses, and unequivocally confirmed by single‐crystal X‐ray diffraction (Fig. 2). Compound 1 contains a γ‐lactone moiety between the 6‐OH function and C(20), and β‐configuration for the 7‐OH group, in contrast to known related diterpenes previously isolated from the S. japonica complex.     

Two new eunicellin diterpenoids from the South China Sea gorgonian Muricella sibogae and their bioactivities

A systematic re-study on gorgonian Muricella sibogae from South China Sea yielded 10 eunicellin-based diterpenoids including two new ones, sibogins C and D (1 and 2). Their structures were elucidated by extensive spectroscopic analyses (1D and 2D NMR, IR and MS) and by comparison with data reported in literatures. All the isolates were tested for cytotoxic and antifouling activities. Compounds 3 and 5 showed significant antifouling activity against the green mussel Perna viridis, and especially 3 was suggested as a potent low-toxic antifouling agent with a large LC₅₀/EC₅₀ value of 18.6. This was the first report on the antifouling activity of the eunicellin-type diterpenoids against the green mussel.     

Nine New Norlabdane Diterpenoids from the Leaves of Austroeupatorium inulifolium

Nine new norlabdane diterpenoids were isolated from the leaves of Austroeupatorium inulifolium collected in Indonesia. All of them have an acyl‐furan unit connected to C(11), and oxygenated functions at C(2) and C(3). The structure elucidations and the assignment of the absolute configurations of the isolated natural products were carried out by extensive spectroscopic analysis and the extended Mosher method, as well as chemical correlations. Antimicrobial activities and cytotoxicity against HL‐60 cells were determined using bioassays.     

Asterolaurins G – J,New Xenicane Diterpenoids from the Taiwanese Soft Coral Asterospicularia laurae

Four new xenicane diterpenoids, asterolaurins G–J ( 1 – 4 , resp.) have been isolated from the Taiwanese soft coral Asterospicularia laurae. Their structures were determined by extensive spectroscopic analyses (UV, CD, IR, ¹H‐ and ¹³C‐NMR, ¹H,¹H‐COSY, HMBC, and NOESY). The cytotoxic activities of all compounds were evaluated.     

Two New Abietane Diterpenoids from the Stems of Clerodendrum kaichianum P. S. Hsu

Two new abietane diterpenoids, named 17‐hydroxyteuvincenone G ( 1 ) and 17‐hydroxyteuvincen‐5(6)‐enone G ( 2 ), together with four known diterpenoids, were isolated from the stems of Clerodendrum kaichianum P. S. Hsu . Their structures were elucidated by extensive NMR and MS analyses, and by comparison with literature data. The new compounds showed significant cytotoxicities against the HL‐60 and A‐549 tumor cell lines.     

New Casbane Diterpenoids from the Hainan Soft Coral Sinularia Species

Six new casbane diterpenoids, sinularcasbanes G–L ( 1 – 6 , resp.) were isolated from the soft coral Sinularia sp. Their structures were established by extensive spectroscopic analyses, especially 2D‐NMR and HR‐ESI‐MS. The configuration was confirmed by CD analyses and by comparison with data reported in the literature. The compounds were evaluated for cytotoxicity against ten human cancer cell lines (H1975, U937, K562, BGC823, MOLT‐4, MCF‐7, A549, HeLa, HL60, and Huh‐7) and showed no activity.     

1H and 13C NMR spectral assignments of some natural abietane diterpenoids

An NMR study of 11 naturally occurring abietane diterpenoids is described. In addition to one‐dimensional NMR methods, including DPFGSE 1D‐NOE spectra, two‐dimensional shift‐correlated experiments [¹H,¹H COSY, ¹H,¹³C‐gHSQC ¹J(C,H) and ¹H,¹³C‐gHMBC ⁿJ(C,H) (n = 2 and 3)] were used for the complete and unambiguous ¹H and ¹³C chemical shift assignments of these substances. Copyright © 2003 John Wiley & Sons, Ltd.