A simple and efficient total synthesis of (±)-danshexinkun A, a bioactive diterpenoid from Salvia miltiorrhiza

An efficient 12-step route for the synthesis of the diterpenoid quinone (±)-danshexinkun A in 23% overall yield from the corresponding highly substituted stilbene using a photocyclization strategy is described.     

A trypanocidal diterpene with novel skeleton from Dracocephalum komarovi

A new diterpene, komarovispirone (1) with a spiro-octahydroindene skeleton, was isolated from Dracocephalum komarovi. The structure was elucidated by extensive analyses of spectral data. Komarovispirone (1) showed trypanocidal activity against epimastigote of Trypanosoma cruzi, the causative agent of American trypanosomiasis, with a minimum lethal concentration of 23 μM.     

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.     

Salviatalin A and salvitrijudin A, two diterpenes with novel skeletons from roots of Salvia digitaloides and anti-inflammatory evaluation

Salviatalin A (1) and salvitrijudin A (2), two diterpenes with novel skeletons, were isolated from the roots of Salvia digitaloides. Their structures were determined using 1D, 2D NMR, and HRESI-MS spectroscopic analyses. Salviatalin A (1) from bioassay-guided fractionation showed a potent inhibitory effect on superoxide anion production in GMLP/CB-activated human neutrophils as well as other anti-inflammatory effects. A plausible biosynthetic pathway is also discussed.     

Thermal degradation products derived from the smoke of Salvia divinorum leaves

Smoking of Salvia divinorum leaves is the most common method for its psychotropic effects. Eleven thermal degradation products, including a new neoclerodane diterpene derivative, were isolated from the smoke of S. divinorum leaves, and their structures were identified by spectroscopic methods. The isolated compounds were evaluated for their binding affinities at the opioid receptors, and salvinorin A is still the most potent kappa opioid receptor agonist.     

A novel labdane diterpene from Acritopappus longifolius

A novel labdane diterpene was isolated from the plant Acritopappus longifolius. The structure of this compound was established by 1D- and 2D-nuclear magnetic resonance spectroscopic techniques and mass spectrometry data. N-Methyl-4-hydroxy-trans-proline, stigmasterol-3-O-β-d-glycoside, and the flavonoids quercetin, luteolin, kaempferol, and rutin were also isolated.     

Kingamide A, a new indole alkaloid from the ascidian Leptoclinides kingi

Chemical investigation of the CH₂Cl₂/MeOH extract from the Australian ascidian Leptoclinideskingi led to the isolation of a new brominated indole alkaloid, kingamide A (1). The planar structure of kingamide A was elucidated following the interpretation of 1D/2D NMR and MS data, and the absolute configuration was determined using Marfey’s method. This is the first report of a natural product from L. kingi.     

Platypodiol a novel clerodane diterpene from Baccharis platypoda

There is an urgent need for effective leishmanicidal drugs to replace or supplement those in current use. Our group has been bioprospecting many Brazilian plants looking for potential new ‘hits’ to combat leishmaniasis. We found that Baccharis platypoda was one of the Asteraceae species that displayed leishmanicidal activity. We now describe the isolation of the new clerodane diterpene (1), named platypodiol after its ethanolic leaf extract. Its structure was determined by detailed NMR and ESI-TOF/MS/MS experiments. Considering the few publications about this species, this result has increased the phytochemical knowledge about B. platypoda.     

Pompanopeptins A and B, new cyclic peptides from the marine cyanobacterium Lyngbya confervoides

A new 3-amino-6-hydroxy-2-piperidone (Ahp) containing peptolide, pompanopeptin A (1), and a novel N-methyl-2-amino-6-(4′-hydroxyphenyl)hexanoic acid (N-Me-Ahpha) containing cyclic pentapeptide connected with a sixth amino acid residue via a rare ureido linkage, pompanopeptin B (2), were isolated from the marine cyanobacterium Lyngbya confervoides collected from the southeastern coast of Florida. Their planar structures were determined by a combination of NMR spectroscopic analysis and mass spectrometry. The absolute configurations were established using advanced Marfey's method and chiral HPLC analysis of the chemical degradation products. Compound 1 selectively inhibited trypsin over elastase and chymotrypsin, with an IC₅₀ value of 2.4 μM; selectivity is conferred by an arginine residue in the cyclic core.     

Crotomacrine, a new clerodane diterpene from the fruits of Croton macrostachyus

A new clerodane diterpene, crotomacrine 1, together with the known crotepoxide were isolated from the fruits of Croton macrostachyus. Their structures were elucidated on the basis of spectral evidence.     

Andrographolactone, a unique diterpene from Andrographis paniculata

Andrographolactone (1), possessing an unprecedented diterpene skeleton, was isolated from the EtOAc extract of the aerial parts of Andrographis paniculata. Its structure was established by NMR, IR, UV, and HRESIMS data and subsequently confirmed by X-ray diffraction analysis. A possible biogenetic pathway of 1 was also proposed. Bioassay showed that 1 exhibited cytotoxic activity.     

A novel polyprenylated phloroglucinol, garcinialone, from the roots of Garcinia multiflora

A novel polyprenylated phloroglucinol garcinialone (1) along with a known compound isoxanthochymol (2) have been isolated from the roots of Garcinia multiflora. The structures of 1 and 2 were elucidated spectroscopically, by 1D and 2D NMR and mass spectrometry.     

Lycopladine H, a novel alkaloid with fused-tetracyclic skeleton from Lycopodium complanatum

A novel Lycopodium alkaloid, lycopladine H (1), with a fused-tetracyclic ring system consisting of an azocane ring connected to a [2,2,2]-bicyclooctane ring and a 3-piperidone ring, was isolated from the club moss Lycopodium complanatum. The structure and relative stereochemistry of 1 were elucidated on the basis of spectroscopic data.     

Withaphysanolide A, a novel C-27 norwithanolide skeleton, and other cytotoxic compounds from Physalis divericata

A novel C-27 norwithasteroid, withaphysanolide A (1) containing a pyran ring was isolated from the aerial parts of Physalis divericata. Four known withaphysalins (2-5) and five physalins (6-10) were also isolated. The structural assignment for 1 was done based on spectroscopic and single-crystal X-ray diffraction data. Logical biosynthetic pathways were postulated. Compounds 6, 7, and 10 displayed potent cytotoxic activity against HCT-116 and H460 human cancer cell lines, with IC₅₀ values less than 2.0 μM.     

Naupliolide, a sesquiterpene lactone with a novel tetracyclic skeleton from Nauplius graveolens subsp. odorus

The aerial parts of Nauplius graveolens subsp. odorus (Schousb) Wikl. afforded a novel sesquiterpene lactone (1) named naupliolide together with the known 6,7,9,10-tetradehydroasteriscanolide 2 and asteriscunolides A-D 3a-d. The structure of compound 1 corresponds to a novel skeleton of 14,15-dimethyl-7,13-dioxotricyclic[6.4.0.0^9,11]dodeca-12,13-olide, and was established on the basis of spectroscopic methods including 2D-NMR. The coexistence of naupliolide 1 together with the structurally related sesquiterpene lactones asterisculolides A-D (3a-d) and 6,7,9,10-tetradehydroasteriscanolide 2, seems to indicate their biosynthetic relationship.     

Premnalatifolin A, a novel dimeric diterpene from Premna latifolia Roxb

Premnalatifolin A (1), a unique icetexane diterpene dimer was isolated from the stem-bark of Indian medicinal plant, Premna latifolia. Its structure and relative stereochemistry were elucidated on the basis of detailed spectroscopic analysis, including HRESIMS and 2D NMR (COSY, HSQC, HMBC, and NOESY) spectra. The compound has dimeric carbon skeleton composed of two icetexane skeletal diterpenes linked via ether bond. Further, premnalatifolin A (1) was also evaluated for its cytotoxicity against cancer cell lines (HT-29, A-431, MCF-7, Hep-G2, PC-3, A-549, B-16 F10, and ACHN), which displayed potent activity against HT-29 and MCF-7 cell lines with the IC₅₀ values of 12.15 and 1.11 μg/mL, respectively.     

Castanolide and epi-castanolide, two novel diterpenoids with a unique seco-norabietane skeleton from Salviacastanea Diels f. pubescens Stib.

Castanolide (1) and epi-castanolide (2), two novel diterpenoids possessing a unique seco-norabietane skeleton, were isolated from Salviacastanea Diels f. pubescens Stib. Their structures and relative stereochemistry were elucidated by extensive NMR analysis and confirmed by single-crystal X-ray diffraction study. A possible biosynthetic pathway of these two compounds was also proposed.     

Neoverataline A and B, two antifungal alkaloids with a novel carbon skeleton from Veratrum taliense

Bioassay-guided fractionation of the ethanol extract of the roots and rhizomes of Veratrum taliense yielded two new and thirteen known steroidal alkaloids. The structures of the two new compounds, neoverataline A and B, were established by extensive spectroscopic analyses to be 3,4-secocevane-4,9-olid-14,15,16,20-tetra-ol-3-oic acid and 3,4-secocevane-4,9-olid-7,14,15,16,20-penta-ol-3-oic acid, respectively, and are a novel carbon skelton. All of the fifteen alkaloids were subjected to in vitro antifungal assays, which showed that the verazine- (veramitaline, stenophylline B, stenophylline B-3-O-β-d-glucopyranoside, veramiline-3-O-β-d-glucopyranoside) and jerveratrum-type (jervine, jervine-3-O-β-d-glucopyranoside) alkaloids exhibited strong antifungal activities against the phytopathogenic fungus Phytophthora capisis with MICs of 160, 120, 160, 80, 80 and 120 μg·L⁻¹, respectively. Furthermore, the verazine-type alkaloids stenophylline B, stenophylline B 3-O-β-d-glucopyranoside and veramiline 3-O-β-d-glucopyranoside were shown to also inhibit the growth of another fungal phytopathogen Rhizoctonia cerealis with MICs of 160, 120 and 120 μg mL⁻¹. The MICs of triadimefon (an antifungal agrochemical used herein as a positive control) against P. capisis and R. cerealis were 120 and 80 μg mL⁻¹, respectively. A preliminary structure-activity relationship regarding these alkaloids has been formulated.     

Gomerones A-C, halogenated sesquiterpenoids with a novel carbon skeleton from Laurencia majuscula

The structures and relative sterochemistry of three halogenated sesquiterpenoids gomerones A-C, 1-3, isolated from Laurencia majuscula are described. They are representative of a novel carbon skeleton, gomerane, biogenetically derived from cyclization of a β-chamigrene precursor. A biogenetic relationship with related sesquiterpenoids from lower terrestrial plants Hepaticae of genera Bazzania, Mannia, Mylia, and Rebouli as well as higher plants of genera Cupressus and Juniperus has been established.     

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.