Marrusidins A and B,New Epimeric Labdane Diterpenes from Marrubium anisodon

Marrusidins A ( 1 ) and B ( 2 ), two new labdane‐type diterpenes, were isolated from the CHCl₃‐soluble subfraction of Marrubium anisodon, along with polyodonine. Their structures were assigned with the aid of ¹H‐ and ¹³C‐NMR spectra and by COSY, HMQC, NOESY, and HMBC experiments.     

Three New, 1‐Oxygenated ent‐8,9‐Secokaurane Diterpenes from Croton kongensis

Three new ent‐8,9‐secokaurane diterpenes, kongensins A–C ( 1 – 3 ), were isolated from the aerial parts of Croton kongensis, together with two known compounds, rabdoumbrosanin ( 4 ) and (7α,14β)‐7,14‐dihydroxy‐ent‐kaur‐16‐en‐15‐one ( 5 ). The structures of the new compounds were elucidated by HR‐MS as well as in‐depth 1D‐ and 2D‐NMR analyses. Compounds 1 – 3 showed an unusual oxygenation pattern, with an AcO or OH group at C(1), in combination with a Δ⁸⁽¹⁴⁾ unsaturation ( 1 ) or an 8,14‐epoxide function ( 2, 3 ).     

Synthetic studies of neoclerodane diterpenoids from Salvia splendens and evaluation of opioid receptor affinity

Salvinorin A (1), a neoclerodane diterpene from the hallucinogenic mint Salvia divinorum, is the only known non-nitrogenous and specific κ-opioid agonist. Several structural congeners of 1 isolated from Salvia splendens (2-8) together with a series of semisynthetic derivatives (9-24), some of which possess a pyrazoline structural moiety (9, 19-22), have been tested for affinity at human μ, δ, and κ opioid receptors. None of these compounds showed high affinity binding to these receptors. However, 10 showed modest affinity for κ receptors suggesting that other natural neoclerodanes from different Salvia species may possess opioid affinity.     

Acylated manoyl oxide diterpenes of Stemodia trifoliata

Two new labdane diterpenes, 6α‐malonyloxy‐ethyl ester manoyl oxide and bis‐6α‐dioxymanoylmalonate, together with the known 6α‐hydroxymanoyl oxide, 6α‐malonyloxymaloyl oxide and betulinic acid were isolated from leaves of Stemodia trifoliata. Their structures were elucidated by spectroscopic studies (IR and HR‐ESI‐MS), including an extensive NMR (COSY, HSQC, HMBC and NOESY) analysis. Copyright © 2010 John Wiley & Sons, Ltd.     

Eight new diterpenoids from soft coral Cespitularia hypotentaculata

Chemical investigation of the soft coral Cespitularia hypotentaculata resulted in the isolation of eight new diterpenes, cespihypotins E-L (1-8). The new metabolites comprise of six verticillene-type diterpenes, one cespitularane derivative, and one derivative with 14-membered lactone ring. The structures were determined through detailed spectroscopic analyses, especially high resolution ESIMS and 2D NMR techniques. The relative stereochemistry was deduced from NOESY spectrum and application of Mosher's ester technique. Immunomodulatory and antiviral activities of 1-8 were tested and evaluated. The biogenetic pathways for 1-8 were also proposed.     

Camphor sulphonic acid mediated quantitative 1,3–diol protection of major Labdane diterpenes isolated from Andrographis paniculata

Phytochemical survey of the methanol extract of the dried aerial parts of Andrographis paniculata led to the isolation of major labdane diterpenes, namely 14-deoxy-11,12-didehydroandrographolide, andrographolide and neoandrographolide. Andrographolide was found to be the major phytoconstituent of the plant which was biologically active. For better physiochemical characteristics and bioefficacy, andrographolide is subjected to semi-synthetic modifications. However, presence of several free hydroxyl groups associated with this molecule make it quite polar and poorly soluble in many organic solvents and hence unsuitable for synthetic modifications. One way of resolving its solubility issue is to protect 1,3-diol quantitatively under mild reaction condition without effecting other functional groups. Reaction conditions were optimised using different solvent systems and catalysts towards this direction. X-ray structure of 3,19-isopropylidene-14-deoxy-11,12-didehydroandrographolide is being reported here for the first time. Isolated compounds and derivatives were confirmed by spectral analysis or X-ray data analysis.     

An Improved Method of Total Synthesis of 2-Methoxypodocarpane-8,11,13-triene

12-Methoxypodocarpane-8,11,13-triene 1 is the key intermediate for synthesis of some important diterpenoids, such as Ferruginol 21, 6,7-dehydroferruginol 31, sugiol 42, 5-epixanthoperol 53 etc. These compounds posses significant bioactivities, such as fungicidal1, antimicrobial1 and cytotoxic activity2. Some methods of synthesis of the title compound 1 were reported, but the process is laborious and the yield is low. In connection with our effort to discovery and develop new anti-HIV drugs, …     

Facile and Simple Synthesis of Ring C Aromatic Diterpenes: Synthesis of (+)-13-Hydroxypodocarpa-8,11,13-triene and (+)-7-Deoxynimbidiol

Alpha alkylation of the nitro group of nitrochromenes was performed by trapping of the nitronate salt generated by NaBH₄ reduction with a Michael acceptor. The adducts were used for the synthesis of spiro-[N-hydroxy]-lactams.     

Synthetic studies on neoclerodane diterpenes from Salvia splendens: oxidative modifications of ring A

Salvinorin A (1), a neoclerodane diterpene from the hallucinogenic mint Salvia divinorum, is the only known naturally occurring non-nitrogenous and specific κ-opioid agonist. Some oxidative modifications of the A ring in the congeners of 1 isolated from Salvia splendens salviarin, splenolide B, splendidin, and in the non-natural 8-epi-salviarin gave new derivatives, some of which were tested as agonists at opioid receptors. However, none of these compounds was active. The presence of the C-18, C-19 lactone could be at the origin of the observed lack of binding affinity.     

Biomimetic Total Synthesis of (±)‐Pallavicinolide A

Piecing it together : The first total synthesis of naturally occurring diterpene pallavicinolide A was achieved. Notable features are highlighted by three key biomimetic transformations: a base‐promoted Grob fragmentation, a singlet oxygen oxidation, and an intramolecular Diels–Alder cycloaddition.