The structures of evonine and neoevonine alkaloids obtained from Euonymus Sieboldiana blume

Evonine (1) and neoevonine (2) were isolated from Euonymus Sieboldiana Blume. The structural studies of the principal alkaloid, evonine were carried out extensively by chemical and spectroscopic methods, resulting in the establishment of the structure of the alkaloid as 1: it is a highly oxygenated sesquiterpene of eudesman type, which is esterified with five moles of acetic acid and evoninic acid (33). The derivatives for the structure determination of 1 are summarized in Charts I–III. Interconversion of the two alkaloids, (1 and 2) was achieved and the structure of neoevonine was elucidated as 2.     

pH-Responsive Cy5 dyes having nucleophilic substituents for molecular imaging

pH-Responsive fluorescent pentamethine cyanine (Cy5) derivatives having nucleophilic substituents were synthesized. Cy5 derivatives 1-O having mercaptopropyl, hydroxypropyl, and aminopropyl groups on an indole nitrogen atom showed pH-dependent equilibria between a fluorescent open-ring structure (1-O) and a non-fluorescent closed-ring structure (1-C) in pH ranges 3–7, 6–7.5, and 8–9, respectively. pH-Responsive dyes 1a-C having a 1,3-thiazinane structure were easily internalized into A549 cells and converted to open-ring structure 1a-O in response to the relatively low pH of acidic compartments in the cells.     

Isolation of a new indoxyl alkaloid,Amoenamide B,from Aspergillus amoenus NRRL 35600: Biosynthetic implications and correction of the structure of Speramide B

A new prenylated indoxyl alkaloid, Amoenamide B (1), was isolated from Aspergillus amoenus NRRL 35600 along with Asperochramide A (2). Although many prenylated oxindole alkaloids, containing bicyclo[2.2.2]diazaoctane cores, have been isolated from the fungus of the genera Aspergillus and Penicillium to date, 1 is the fourth compound with the indoxyl unit containing the cores. During the structure elucidation of 1, we found that the planar structure matched to that of Speramide A (3), isolated from A. ochraceus KM007, but the reported structure of 3 was incorrect and turned out to be that of Taichunamide H (4), recently isolated from A. versicolor HDN11-84.     

Antimicrobial constituents of the sponge siphonodictyon coralliphagum

The burrowing sponge Siphonodictyon coralliphagum contains two phenolic aldehydes, siphonodictyal-A (1) and siphonodictyal-B (2). The structure of siphonodictyal-A (1) was determined by interpretation of spectral data and the synthesis of a derivative. The structure of siphonodictyal-B (2) resulted from interpretation of spectral data and the synthesis of a degradation product. Both compounds exhibit antimicrobial activity.     

Attenuol—structure,stereochemistry and synthesis

A new lignan, attenuol, isolated from Knema attenuata (Wall.) Warb., has been assigned structure (1) on the basis of spectral data. Lignan (1) and the stereoisomer (4) (2-epiattenuol) have been synthesized and the structure assigned to attenuol has been confirmed.     

Structural study of tubeimoside i,a constituent of tu-bei-mu

The structure of Tubeimoside I isolated from the bulb of Bolbostemma paniculatum [Maxim] Franquet (Tu-bei-mu) was determined as 1 mainly by comparative NMR studies of 1 and its degration products. The compound 1 has inter-saccharidechain bridging by a dicrotalic acid to from a unique macrocyclic structure.     

Katorazone,a new yellow pigment with a 2-azaquinone-phenylhydrazone structure produced by Streptomyces sp. IFM 11299

An unusual alkaloid with a 2-azaquinone-phenylhydrazone structure, katorazone (1), and other metabolites were isolated from the ethyl acetate extract of Streptomyces sp. IFM 11299. The chemical structure of katorazone (1) was elucidated by 1D and 2D NMR analyses together with HR-ESI mass spectrometry. Katorazone (1) showed a synergistic effect in combination with TRAIL and decreased the viability of human gastric adenocarcinoma (AGS) cells.     

Chemical studies of marine invertebrates—XXVIII: Diterpenes from clavularia inflata (coelenterata,octocorallia, stolonifera)

The presence of terpenoids in the order Stolonifera has been established by the isolation of three novel diterpenes, 1α,4β-dihydroxyclavular-17-ene (1), 4β-hydroxyclavulara-1(15),17-diene (2) and 3α.4β-dihydroxyclavulara-1(15), 17-diene (3) from Clavularia infiata. The structure of 1 has been determined by X-ray diffraction analysis and those of 2 and 3 by chemical intercorrelation with 1.     

Asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives

We herein report an asymmetric synthesis of α,α-disubstituted α-amino alcohol derivatives 3, key intermediates of a novel immunomodulator, using enzymatic desymmetrization of 2-alkyl-2-tert-butoxycarbonylamino-1,3-propanediols 1a and 1b. This method makes it possible to prepare a chiral analogue of FTY720 4. These synthetic procedures allow for a broad structure variation in order to evaluate structure–activity relationships and the mechanism of action for sphingosine 1-phosphate-1 (S1P₁) receptor agonist.     

Hydrogen-bond-assisted supramolecular 1-D tape-like structures of mesogenic bis-pyrazoles

Two new series of isomeric bis-pyrazoles 1a–b are prepared, characterized, and their mesomorphic properties investigated. These pyrazoyl derivatives were obtained from the condensation of α,β-diketones 2a–b with hydrazine monohydrate in refluxing THF. Two single crystallographic structures of compounds mesogenic 1a (n=14) and nonmesogenic 1b (n=8) were determined by X-ray analysis. Both 1a–14 and 1b–8 crystallize in a triclinic space group P?1 and monoclinic C2/c group, respectively. An extended H-bonded structure was formed in both crystal lattices, giving a pseudo 1D-polymeric tape-like structure. Derivatives 1a exhibited smectic A/C mesophases, in contrast, derivatives 1b were all nonmesogenic. The difference in mesomorphic behavior was attributed to the between linear conformation and the coplanarity of the five rings over than in 1a. The correlation between the molecular structures and the mesomorphic properties is discussed.     

Structure determination of lavendamycin- a new antitumor antibiotic from streptomyces lavendulae

The structure elucidation of lavendamycin (1a), a new antitumor antibiotic related to streptonigrin (2) is described. The NMR spectra of 1a and several model compounds 3,4 < and 5a-b are also discussed.     

The configuration and conformation of isogermacrone. The significance of crossed conformations in olefinic cyclisations

The 9,10-double bond of isogermacrone was assigned the Z configuration based on¹HNMR nOe measurements and the ¹³CNMR shifts of the methyl groups. An X-ray crystal structure determination verified this conclusion and the structure of isogermacrone was shown to be (2Z, 7E)-3,7-dimethyl-10(1-methylethyl-idene)-2,7-cyclodecadien-1-one (1). The molecule crystallised in an anti conformation, which according to ¹HNMR is the predominant conformation in solution at room temperature.¹H NMR spectroscopy revealed the presence of syn and anti conformers in the ratio 1:2 at about -60°. The stereochemistry of the base-induced formation of isogermacrone 1 from germacrone 2 and that of the transannular cyclisation of isogermacrone are discussed.     

Clitidine,a new toxic pyridine nucleoside from clitocybe acromelalga

From a poisonous mushroom, Clitocybe acromelalga, a new nucleoside clitidine (1) was isolated as a toxic principle. The structure was deduced to be 1 from spectral data and chemical degradation studies. Synthesis of 1 through condensation of methyl 4-aminonicotinate with 3, 5-di-O-benzoyl-D-ribofuranosyl chloride confirmed the structure, including absolute configuration.     

The structures of macbecin I and II : New antitumor antibiotics

Macbecin I 1, C₃₀H₄₂N₂O₈, and macbecin II 2, C₃₀H₄₄N₂O₈, were shown to be 2,6-disubstituted benzoquinone and hydroquinone derivatives by an oxidation-reduction relationship, UV. ¹H and ¹³C NMR spectra. Alkaline methanolysis of 1 gave a 2-aminobenzoquinone derivative 5, suggesting an ansa-structure for 1, and acid hydrolysis of 1 gave decarbamoyl products 9,10 and 11, indicative of the location of carbamoyloxy group in allylic position. Spin decoupling studies on 1,3 and 5clarified the partial structures [A], [B], [C] and [D]. From their mutual disposition two structures 1a and 1b, were proposed out of which 1a has been selected for the structure of 1 on the basis of the structure of oxidative degradation product 12. X-Ray analysis of the bromoacetyl derivative of 1 confirmed the above proposed structure and determined the absolute stereochemistry of 1 and 2.     

Naturally-occurring acetylenic compounds and derivatives : Regio- and stereocontrolled chloroformylation of 2-(1-propynyl)thiophene and 2-phenyl-5-(1-propynyl)thiophene

2-Phenyl-5-(1-propynyl)thiophene (1), isolated from Coreopsis grandiflora, and 2-(1-propynyl)thiophene (5), an immediate precursor in the synthesis of junipal (2), were synthesized in high yield by a Pd-catalyzed reaction between propyne and 2-iodo-5-phenylthiophene (4) or 2-iodothiophene (6), respectively. Reaction of 5 with the Vilsmeier reagent derived from POCl₃ and N-methylformanilide (MFA) afforded a mixture from which it was possible to isolate (E)-3-chloro-2-methyl-3-(2-thienyl)acrolein (10) in 37.7% yield. The structure and stereochemistry of 10 was unequivocally established by X-ray diffraction of a single crystal of the 2,4-dinitrophenylhydrazone of 10. GLC analysis showed that 10 was contaminated by ca 7% with an isomer to which, on the basis of ¹H-NMR and mass spectra, the structure of (Z)-3-chloro-2-methyl-3-(2-thienyl)acrolein (11) was attributed.Contrary to what was expected from the literature, junipal (2) represented only a minor component in the reaction mixture obtained by the Vilsmeier reaction on 5.Reaction of 1 with POCl₃ and MFA afforded (44.6% yield) a (E)-3-chloro-2-methylacrolein to which the structure 15 was attributed. Compound 15 was also contaminated by ca 10% of an isomer 16, which very probably corresponded to the (Z)-stereoisomer of 15.     

Novel pyrimidine and its triazole fused derivatives: Synthesis and investigation of antioxidant and anti-inflammatory activity

In the present study, we have carried out the synthesis of novel dihydropyrimidinecarbonitrile (1a–c), its dimethylated adduct (2a–c), and hydrazine derivative (3a–c) of 2a–c and its triazole fused derivatives (4a–c, 5a–c and 6a–c). The structure of newly synthesized compounds was confirmed by IR, ¹H NMR, mass spectral data and elemental analysis. Further the novel derivatives were investigated for their in vitro antioxidant and anti-inflammatory activity. The results revealed that some of the tested compounds showed potent antioxidant and anti-inflammatory activity. The mass spectral pattern of 6a has been investigated in order to elucidate the structure.     

Non-terpenoid C-15 metabolites from the red seaweed Laurencia pinnatifida

The structures of absolute configurations of the halogenated vinyl acetylenes which are natural products from the red alga Laurencia pinnatifica (Gmal. Lamour) are described. The structure of trans- pinnatifidenyne 2 was determined by spectral, chemical and X-ray diffraction analyses. The structure of cis-pinnatifidenyne 1 is based on spectral comparison and chemical interconversion with the trans-isomer 2. The structure of the acyclic trienyne 8 was secured as: (6R,7R)-3-cis, 9-cis,12-cis,6-acetoxy,7-chloropentadeca-3,9,12-trien-1-yne by synthesis from cis-pinnatifidenyne 1. The reactivity of these compounds to various conditions of catalytic hydrogenation has been examined in detail.     

Three iodometalate organic-inorganic hybrid materials based on methylene blue cation: Syntheses,structures, properties and DFT calculations

The functional dye of methylene blue (MB) has been employed for seeking new organic–inorganic hybrid photochromic materials. Although the photochromism has not been observed yet, three iodometalate compounds, namely (MB) (PbI₃) (DMF) (1), (MB)₄(Cu₂I₄)₂ (2), and (MB)₃(Bi₂I₉) (DMF)₂ (3), have been synthesized and characterized. The iodometalate anion features as a [PbI₃]_∞⁻ chain in 1, a dinuclear unit of Cu₂I₄^2- in 2, and a dinuclear unit of Bi₂I₉³⁻ in 3. Due to the synergy of cations and anions, the MB⁺ cations present supramolecular column stacks in 1 and 3, but a novel supramolecular octamer structure in 2. Their thermogravimetric analyses reveal that the polymeric inorganic anion structure is helpful to increase the stability of cation whereas the discrete structure is adverse. For seeking some clues which is significant to searching new photochromic systems, the density functional theory (DFT) studies have been performed on 1, in which the electronic structure analyses suggests that the stacking mode of cations and anions could be also an important factor influencing the charge transfer between them. In addition, dielectric hysteresis loop testing has been performed on 1 due to its polar space group of Cc.     

Polyaza-macrocycles of cyclophane type: Synthesis,structure of a chloroform inclusion complex and anion binding.

Polyazamacrocycles (1)–(7) have been obtained via efficient (amine + aldehyde) polycondensation processes. The tetraimine (1) forms a chloroform inclusion complex whose crystal structure has been determined; the protonated tetraamine (5) binds dicarboxylate substrates.     

La polysilylation directe: une voie rapide d'accès à des modèles d'encombrement stérique très élevé

Reductive tetrasilylation of t-butyl-, trimethylsilyl- and o-bis(trimethylsilyl)benzenes with Me₃SiCl/Li/THF was carried out in high yields, giving the corresponding cyclohexene derivatives [one (1), two (2a and 2b) and one (3) isomers, respectively]. X-Ray structure analysis of 1 and comparison of NMR (¹H, ²⁹Si) data of the four products allowed complete structure assignments. The presence of a t-Bu or Me₃Si group in the vinylic position requires that the Me₃Si group attached to the vicinal Csp³ atom be in the pseudo-axial position. For the first 1,2,3,4,5,6-hexasilylated cyclohexene 3 we propose a pseudo-chair structure in which the four silyl groups attached to Csp³ atoms are in pseudo-axial positions.