Two new dimeric naphthoquinones with neuraminidase inhibitory activity from Lithospermum erythrorhizon

The crude methanol extract of roots of Lithospermum erythrorhizon was subjected to successive chromatographic fractionation which afforded two new dimeric naphthoquinone derivatives shikometabolin E (2) and shikometabolin F (3) as well as one known compound shikometabolin A (1). The structures of compounds 1–3 were elucidated by using UV, MS, 1D and 2D NMR spectroscopic analysis. The two new dimeric naphthoquinone derivatives showed significant neuraminidase inhibitory activities.     

A Novel Dimeric Eremophilane from Ligularia virgaurea spp. oligocephala

A novel dimeric eremophilane, ligulolide B, was isolated from the alcoholic extract of the whole plant of Ligularia virgaurea spp. oligocephala. The structure was elucidated by various spectroscopic methods including intensive 2D NMR techniques （^1H-^1H COSY, gHMQC, gHMBC and ^1H-^1H NOESY） and HR-ESI-MS.     

A new dimeric iridal triterpenoid from Belamcanda chinensis with significant molluscicide activity

An unprecedented dimeric triterpenoid, designated dibelamcandal A, with a six-membered ring linking two iridal type triterpenoid nuclei, was isolated from the rhizome of Belamcanda chinensis. Its structure was determined by extensive spectroscopic measurements, including IR, ESI-MS, HR-ESI-MS, and 1D and 2D NMR. It demonstrated significant molluscicide activity against Pomacea canaliculata.     

A novel dimeric diarylheptanoid from the rhizomes of Alpinia officinarum

A novel dimeric diarylheptanoid,named alpinin A(1),along with two known compounds,1,7-diphenyl-5-ol-3-heptanone and 7- (4’-hydroxy-3’-methoxyphenyl)-l-phenyl-4-heptene-3-one,were isolated from the rhizomes of Alpinia officinarum Hance.The structure of compound 1 was elucidated on the basis of spectral analysis,including HR-IT-TOF-MS,1D and 2D NMR.And a possible biogenetic pathway had been proposed for 1.     

A novel dimeric procyanidin glucoside from Polygonum aviculare

A novel dimeric procyanidin glucoside,catechin 3-O-acetate-(4 α→8)-catechin 3-O-acetate-3’-O- β-D-glucopyranoside(1), along with five flavonoids and one lignan were isolated from the aerial parts of Polygonum aviculare.Their structures were elucidated by spectroscopic analyses including 1D,2D NMR,MS and CD methods.     

Versatile formation of [2]catenane and [2]pseudorotaxane structures; threading and noncovalent stoppering by a self-assembled macrocycle

A self-assembled dimeric macrocycle between 4,4'-bis(4-pyridylmethoxy)biphenyl (L) and (en)Pd(NO(3))(2) was constructed, and its interactions with cyclodextrins of different cavity size resulted in the formation of [2]catenane and [2]pseudorotaxane systems, respectively. The structures were identified by 1D and 2D NMR spectroscopy and cold spray ionization mass (CSI-MS) spectrometry.     

Four new dimeric triterpene glucosides from Sanguisorba officinalis

In search for bioactive compounds from the roots of Sanguisorba officinalis L. (Rosaceae), four new dimeric triterpene glucosides, namely sanguidioside A, B, C, and D (1-4) were isolated. Alkaline hydrolysis of 1-2 afforded the corresponding dimeric aglycones (1a and 2a). Meanwhile, a ready intra-molecular transesterification was observed, providing dimeric triterpenes 1b and 2b. Alkaline hydrolysis of the crude dimmeric saponin also provided a new dimeric triterpene, sanguidiogenin (9). The structures of all these compounds are elucidated via spectroscopic and chemical methods, and are further confirmed by the X-ray diffraction analysis of the dimeric aglycone 2a. Compound 3 represents the first dimeric saponin of an oleanolic acid and an ursonic acid derivative, while compound 4 is the first dimeric saponin of oleanolic acid derivatives.     

Three new dimeric diterpenes from Rhododendron molle

Birhodomolleins A-C (1-3), three novel diterpenoids dimerized from two grayanane diterpenes through an oxygen bridge, were isolated from the flowers of Rhododendron molle. Their structures were elucidated by interpretation of their 1D and 2D NMR and other spectroscopic data. Birhodomollein A (1) contains a rare chloro-substitution on one of the grayanane moieties. These are the first examples of dimeric diterpenes from the Ericaceae family.     

Dimeric Coumarin and Phenylpropanoids from Clausena lenis

A new dimeric coumarin, diseselin B ( 1 ), and three new phenylpropanoids, lenisin A–C ( 2 – 4 ), together with eight known O‐terpenoidal coumarins, were isolated from the aerial part of Clausena lenis. Lenisin A ( 2 ) was also isolated from the aerial part of C. excavata. The structures were elucidated on the basis of 1D‐ and 2D‐NMR experiments (HMQC, HMBC, and ¹H,¹H‐COSY).     

Aurasperone F--a new member of the naphtho-gamma-pyrone class isolated from a cultured microfungus, Aspergillus niger C-433

A novel dimeric naphtho-gamma-pyrone, named aurasperone F (1), was isolated from the fermentation broth of the culture extracts of Aspergillus niger C-433, isolated from grapes, along with the known compounds fonsecin (2), aurasperone B (3), aurasperone C (4), aurasperone D (5) and aurasperone E (6). The chemical structure of the new natural product was established by extensive one- and two-dimensional NMR spectroscopic studies (1H, 13C, COSY, HMQC, 1D NOE spectra), as well as on the UV, MS and IR spectral analysis.     

Silvaglenamin—a novel dimeric triterpene alkaloid from Aglaia silvestris

An unusual dimeric triterpene structure with two dammarane units linked with an enaminic -NH- group was isolated from the root extract of Aglaia silvestris. The structure was elucidated by 1D and 2D NMR analysis and ESI mass spectrometry.     

Bishyoscyamine, one unusual dimeric tropane alkaloid from Anisodus acutangulus

One unusual dimeric tropane alkaloid, bishyoscyamine, was isolated from the roots of Anisodus acutangulus, whose structure including the absolute stereochemistry was unambiguously determined based on extensive 1D NMR and 2D NMR, HR-ESI-MS [α]D and CD spectroscopic analyses. To our knowledge, bishyoscyamine is the first example of tropane alkaloid dimer condensed by a C-N bond.     

meso-tetraphenylporphyrin dimer derivatives as potential photosensitizers in photodynamic therapy. Part 2

Studies on the synthesis, singlet oxygen and fluorescence yields and pharmacokinetic properties of three different dimeric porphyrins with an amide linkage (D2-D4) are described and compared with the results recently reported for a dimeric porphyrin (D1). The pharmacokinetic behavior of all dimers were examined in Balb/c mice bearing MS-2 fibrosarcomas. The maximal efficiency and selectivity of photosensitizer accumulation in each tumor tissue takes place at 24 h after drug administration of 1.0 mg kg-1 into DL-alpha-dipalmitoylphosphatidylcholine liposomes by intravenous injection. Since the dimeric porphyrins exhibit high quantum yields of singlet oxygen generation, long triplet lifetimes and high photostability, the results obtained suggest that the evaluated dimeric structures may be promising candidates for further use in PDT experiments. The results also allow the possibility to establish a correlation between the chemical structure of the dyes and the efficiency/selectivity of the tumor accumulation and can be used for building up optimal photosensitizing agents for tumors.     

Lignans from the Bark of Zanthoxylum planispinum

A new dimeric lignan, named biplanispine A ( 1 ) which represents the first example of a dimeric 2,6‐diaryl‐3,7‐dioxabicyclo[3.3.0]octane skeleton from a Rutaceae plant, together with 13 known lignans 2 – 14 , was isolated from the bark of Zanthoxylum planispinum. Their structures were elucidated by spectroscopic methods, especially 2D‐NMR techniques. All isolated compounds were evaluated for their antibacterial activities by the disc diffusion method. Compounds 7 and 9 showed interesting antibacterial activities at 200 μg/disc; they were as effective as kanamycin sulfate at 10 μg/disc against Staphylococcus aureus and Bacillus subtilis.     

New naphthopyrones from aspergillus fonsecaeus

Four new dimeric naphthopyrones, fonsecinones A (7), B (8), C (9), and D (10), and two known ones, aurosperones A (6) and B (11), were isolated from Aspergillus fonsecaeus (N.R.R.L. 67, 0 16-1).     

Juglanones A and B: Two Novel Tetralone Dimers from Walnut Pericarp (Juglans regia)

Two novel tetralone dimers, with an O‐bridge, named juglanones A and B ( 1 and 2 , resp.), were isolated from the AcOEt extract of walnut pericarps. These compounds are the first examples of O‐bridged dimeric tetralones. Their structures were determined by spectroscopic methods, including HR‐TOF‐MS, and 1D‐ and 2D‐NMR. Biological evaluation of these two isolates against a number of human cancer cell lines is also described.     

Molecular tectonics: self-complementary supramolecular Se...N synthons directing assembly of 1D silver chains into 3D porous molecular architectures

Reaction of 2,1,3-benzoselenadiazole (bsd) with AgNO3 results in the formation of a novel model example of a Se...N synthon directed molecular network of different polymorphs at different temperatures. Alpha-[Ag(bsd)2(NO3)] x 0.5bsd formed at ambient temperature, has a 3D porous molecular network constructed with monomeric [Ag(bsd)2(NO3)] motif, and has 1D channels that are encapsulated with 1D arrays of two-fold-disordered dimeric (bsd)2 guests aggregated by the self-complementary nonbonded Se...N interactions. This is the first molecular net directed by supramolecular Se...N synthons. The second polymorph, beta-[Ag(bsd)2(NO3)] x 0.5bsd, formed from an analogous reaction at 50 degrees C, contains a similar 3D molecular network constructed with tetrameric [Ag4(bsd)8(NO3)4] motif and 1D arrays of well-ordered dimeric (bsd)2 guests are encapsulated in the channels. Such ordered (bsd)2 dimers provide an excellent simplified dimeric model for MO calculations of intermolecular nonbonded Se...N interactions.     

Interaction between dyes and polyelectrolytes. XI. Photoreduction of methylene blue bound to potassium polystyrenesulfonate

The effect of potassium polystyrenesulfonate (PSSK) on the quantum yield (Φ) in the photoreduction of methylene blue (MB) by allylthiourea was investigated. MB was bound to PSSK in monomeric, dimeric, or slightly aggregated form, depending on the polyanion–dye ratio (P/D). At a relatively lower P/D in which most MB molecules were bound to PSSK in dimeric or slightly aggregated form, the value of Φ was smaller than that at a P/D of zero. On the other hand, at a higher P/D, in which most MB molecules were bound to PSSK in monomeric form, the value of Φ was larger than that at a P/D of zero. It was suggested that the lower reactivity of dimeric or slightly aggregated MB on PSSK was caused by the length of its lifetime which is shorter than that of the monomeric form. It was also suggested that the increase in Φ at higher P/D was caused by the decreased deactivation of the triplet excited MB by the ground-state MB.     

A New Dimeric Secoiridoid Glycoside from the Leaves of Olea ferruginea Royle

A new dimeric secoiridoid glycoside, trivially named oleferrugine B ( 1 ), has been isolated from the AcOEt‐soluble part of the MeOH extract of leaves of Olea ferruginea Royle . The structure of the isolated compound was established on the basis of ESI‐MS fragmentation patterns, and 1D‐ and 2D‐NMR techniques, including ¹H‐ and ¹³C‐NMR, HSQC, ¹H,¹H‐COSY, HMBC, and NOESY experiments, and by comparison with literature data.     

Shuangancistrotectorines A–E,Dimeric Naphthylisoquinoline Alkaloids with Three Chiral Biaryl Axes from the Chinese Plant Ancistrocladus tectorius

Five novel dimeric naphthylisoquinoline alkaloids, shuangancistrotectorines A ( 3 a ), B ( 3 b ), C ( 4 ), D ( 5 a ), and E ( 5 b ), have been isolated from the twigs of the Chinese plant Ancistrocladus tectorius. Their absolute stereostructures were determined by spectroscopic and chiroptical methods in combination with quantum chemical CD calculations. In contrast to all other known dimeric naphthylisoquinoline alkaloids, in which the central binaphthalene axis is 6′,6′′‐coupled and thus not rotationally hindered, the dimers described here are linked via the sterically more hindered 3′,3′′‐ or 1′,1′′‐positions of the naphthalene units. They are thus the first such dimers—and even the very first natural products at all—that have three consecutive stereogenic axes. Hence, including the stereogenic centers, they have up to seven stereogenic units in total. Some of the compounds, in particular shuangancistrotectorines A, B, and D ( 3 a , 3 b , and 5 a ) exhibit very good, and specific, antiplasmodial activities.