Studies on the constituents of asclepiadaceae plant—LVII: The structures of six glycosides,wilfoside c1n,c2n,c3n,c1g,c2g and c3g,with novel sugar chain containing a pair of optically isomeric sugars

Six new glycosides named wilfoside C3N (l), C1N (2), C2N (3), C3G (4), C1G (5) and C2G (6) were isolated from Cynanchum wilfordi hemsley (Asclepiadaceae) and their structures were deduced on the basis of the chemical and spectral evidence. It is quite unusual that 2, 3, 5 and 6 include both D-cymarose and L-cymarose in each sugar chain.     

On the photoisomerization of bicyclo[3.2.n]dienones

Two bicyclo[3.2.n]dienones, which differ from one another only by the presence or absence of an O atom as the “n” bridge, show very different pbotoisomerization behavior. Irradation of hexamethyl-8-oxabicyclo[3.2.1]octadienone 12 gives endo-6-acetylpentamethylbicyclo[3.1.0]hexenone 16, probably via an initial [1,3] sigmatropic rearrangement (Scheme 3). In contrast, hexamethylbicyclo[3.2.0]heptadienone 14 photoisomerizes via an initial [3,3]-sigmatropic rearrangement, the isolated product being the relatively stable cyclopentadiene-ketene 26. The methylene analog of 14 (i.e.32) rearranges similarly. giving allene 33 and alkyne 34. The mechanisms of these photoisomerizations are discussed.     

Dactylospongiaquinone, a new meroterpenoid from the Australian marine sponge Dactylospongia n. sp.

Chemical investigation of the sponge Dactylospongia n. sp. collected near Mooloolaba, S.E. Queensland, has led to the isolation of dactylospongiaquinone (7) together with the known quinones (2-5). The new metabolite 7 possesses a different carbon framework from the known dictyoceratidaquinone (9) and is suggested to possess a cis-fused ring junction by extensive NOESY studies combined with molecular modelling calculations. The relative stereochemistry of the previously described cyclospongiaquinone-1 (3) and dehydrocyclospongiaquinone-1 (4) is also assigned on the basis of NOESY analyses. Full NMR spectroscopic assignments are provided for all compounds.     

Silylation as a protective method in acetylene chemistry. : Syntheses in the polyeneyne series,R3Si(CC)n(CHCH)4(CC)nSiR3 and H(CC)n(CHCH)4(CC)nH (n = 1, 2)

The Grignard reagents R₃Si(CC)_nMgBr (R = Me, n = 1; R = Et, n = 1,2) couple with cyclooctatetraene dibromide 1 in THF to give, as major products, the silyl-stabilised E, Z, Z, E-polyeneynes, Me₃SiCC(CHCH)₄CCSiMe₃3a, Et₃SiCC(CHCH)₄CCSiEt₃4a and Et₃Si(CC)₂(CHCH)₄(CC)₂SiEt₃6a together with minor proportions of configurational isomers Z, E, Z, Z 3c, all -E 3b, 4b, 6b and compounds in which a bicyclo-octadiene structure 2, 5 and 7 is retained. Irradiation converts the cis(Z)-rich isomers e.g. 3c into the all-trans(E) products. Treatment of the bissilyl compounds 3, 4 and 6 with aqueous base liberates the respective parent polyeneynes, H(CC)_n(CHCH)₄(CC)_nH, in each case.     

Flash vacuum thermolysis of dispiro[2.2.n.2]alkadienes

The Flash Vacuum Thermolysis (FVT) of dispiro[2.2.6.2]-tetradeca-4,13-diene (7a), dispiro[2.2.5.2]trideca-4,12-diene (7b) and dispiro[2.2.2.2]deca-4,9-diene (7e) at 500 – 750 °C is reported. The complicated reaction mixture from 7a and 7b (Scheme 3) included at lower temperatures vinylspiroalkadienes 9, ethylidenespiroalkadiene 10b, β-ethylcycloalkabenzenes 11, while at higher temperatures, p-n-alkyl- (5) and p-sec-alkylstyrenes 14 and p-divinylbenzene (15) dominated. Product formation is explained by invoking diradicals 8, 6 and 12 as well as the cyclophanes 1 and 13 as intermediates. For 7e, the product mixture was less complicated and consisted of p-ethylstyrene (5e), 15 and, unexpectedly, p-isopropylstyrene (14e) which contains one carbon more than the starting material. The analysis and interpretation of product formation largely confirms previously suggested reaction pathways and furnishes further interesting details. However, new and unexpected features are also encountered, especially in the fragmentations of 1 and 13 which may stimulate future investigations on the thermal behaviour of these relatively simple hydrocarbons.     

Construction of [Cu n I n ]-based coordination polymers via flexible benzimidazolyl-based ligands

Four new [Cu _n I _n ]-based coordination polymers, [{ Cu₄(µ₃-I)₄(mbbm)₂}·2DMF] _n (1), [(CuI)₂(mbbm)₂] _n (2), [{Cu₂(µ-I)₂-(ebbm)₂}·2MeCN] _n (3), and [Cu₂(µ-I)₂(prbbm)₂] _n (4), were prepared from solvothermal reactions of CuI with three flexible ligands [(bzim)(CH₂) _n (bzim)] (bzim = benzimidazole; n = 1, mbbm; n = 2, ebbm; n = 3, prbbm). These compounds were characterized by elemental analysis, IR and X-ray crystallography. 1 consists of cubanelike [Cu₄(µ₃-I)₄] fragments that link the neighboring ones via mbbm bridges to form a 1D ladder-type chain. 2 contains mononuclear [CuI] fragments that are bridged by mbbm ligands to yield a 1D zigzag chain. 3 or 4 contains a [Cu₂(µ-I)₂] dimeric fragment, which works as a four-connecting node to link its four equivalent ones to form a 2D (4,4) network (3) or acts as a two-connecting node to connect its two equivalent ones via two pairs of prbbm bridges to form a 1D double chain (4). The photoluminescent properties of 1–4 in the solid state at ambient temperature were investigated.     

Novel 1D coordination polymer {Tm(Piv)3}n: Synthesis,structure, magnetic properties and thermal behavior

The new 1D coordination polymer {Tm(Piv)₃}_n (1), where Piv=OOCBu^t?, was synthesized in high yield (>95%) by the reaction of thulium acetate with pivalic acid in air at 100 °С. According to the X-ray diffraction data, the metal atoms in compound 1 are in an octahedral ligand environment unusual for lanthanides. The magnetic and luminescence properties of polymer 1, it’s the solid-phase thermal decomposition in air and under argon, and the thermal behavior in the temperature range of ?50…+50 °С were investigated. The vaporization process of complex 1 was studied by the Knudsen effusion method combined with mass-spectrometric analysis of the gas-phase composition in the temperature range of 570–680 K.     

Conformational behavior of dithia[n.3.3](1,3,5)cyclophanes and dithia[n.3.3](1,2,6)cyclophanes

The conformational behavior of a series of crown-fused dithia[n.3.3](1,2,6)cyclophanes (126-CPs) and dithia[n.3.3](1,3,5)cyclophanes (135-CPs) was investigated by variable-temperature ¹H and ¹³C NMR spectroscopy, X-ray crystallography and density functional theory (DFT) calculations. Single crystal X-ray structure analysis showed that two thia-bridges in 126-CPs adopted a pseudochair-pseudochair (cc) conformation and the cyclophane decks underwent a ring-tilting motion in the case of [10.3.3](1,2,6)cyclophane (1a). In contrast, the thia-bridges in 135-CPs took both cc and pseudoboat-pseudochair (bc) conformations, and the ring-tilting process was also found in [10.3.3](1,3,5)cyclophane (2a). Variable temperature ¹H NMR study revealed that there was no wobbling-motion for two thia-bridges in 126-CPs while thia-bridges in 135-CPs experienced a wobbling-process with a conformational barrier of 9.21 and 8.80 kcal mol⁻¹, respectively, for 2a and [13.3.3](1,3,5)cyclophane (2b). DFT calculations for the two cyclophanes series revealed that 126-CPs preferred a cc conformation which was consistent with the experimental observation; similarly, 135-CPs took a preferential cc conformation, agreeing with 2a having a predominant cc conformer (cc:bc ratio=70:30), but not 2b having a predominant bc conformer (cc:bc ratio=15:85) in the solid state.     

Synthesis,Structure and Characterisation of One Two-Dimensional Layered Vanadium Tellurite [H2en] n [V2Te2O10] n

A two-dimensional layered organic templated vanadium tellurite, [H₂en] _n [V₂Te₂O₁₀] _n 1 (en = ethanediamine) has been synthesized through a conventional hydrothermal reaction and structurally characterized by X-ray powder diffraction, X-ray single-crystal diffraction analysis, FTIR, UV-DRS, thermogravimetric analysis (TGA), thermal-dependent 2D-IR correlation spectroscopy (2D-COS IR) and element analysis. Compound 1 is allomorphic to [H₂en][V₂Te₂O₅]₂ which is reported by Jung et al. According to the data of compound 2 got from the Cambridge Crystallographic Data Centre (CCDC) and Mercury, we optimize the H-bondings of compound 2. The two compounds are compared in weak interactions, IR and TGA characterizations, and UV and thermal-dependent 2D-IR spectroscopy of compound 1 was supplementary reported. Furthermore, we calculated the topology type of both two compounds.     

Zum verhalten von steroiddienen gegenüber Pb(OAc)4-n(N3)n

The reaction of 7-dehydrocholesterylbenzoate with the title reagent at a temperature of ?20° yields 50% 1, 3β-benzoyloxy-5α,14α-diazidocholest-7-en-6-one, and 25% 2, 3β-benzoyloxy-5α- azido-cholest-7-en-6-one. Under the same conditions 3,5-cholestadiene yields 3α,6β-diazidocholest-4- ene (40%; 3) and 6β-azido-cholest-4-en-3-one (6%; 4). The structure elucidation of the compounds 1–4 is supported by spectroscopy.     

Phosphorus heterocycle synthesis by RPX2 · ALX3 addition to [1,n]dienes—IX : The synthesis and structure of several oxaphosphabicyclic compounds

Several oxaphosphabicyclic compounds were synthesized by the reaction of methyl dihalophosphane under various conditions with 1,6-diketones and βγ-unsaturated ketones. The structure of one of the new compounds (11) was established by X-ray diffraction analysis. The ¹H- and ¹³C-NMR spectra of the new compounds, which, except for 11, served for their structure elucidation, are discussed.     

Benzannelated [9] and [13] annulenes: Formation,structural properties and the effect of benzannelation on the aromaticity of the (4n+2) π anionic sy

The synthesis of benzannelated [9] and [13] annulenenes is described, 1,2:3,4-dibenzocyclononatetraene 3 and its diphenyl derivative 10 show upon deprotonation the initial formation of a non-planar partially delocalized anions 4 and 11 respectively, which undergo into the planar aromatic-diatropic dibenzocyclononatetraenyl anions 4a and 12. The immediate formation of the aromatic 1,2:5,6 - dibenzocyclononatetraenyl anion 14 upon deprotonation of 1,2:5,6 - dibenzocyclononatetraene 13 precludes peri H-H repulsions in the aromaticity development of the dibenzocyclononatetraenyl anions. The deprotonation of tetrabenzo[13]annulene 15 afforded anion 17, which shows reduced diatropic character as compared with non-benzannelated[13] annulenyl anion. The spatial arrangement of 17 is discussed.     

Umsetzungen von Δ5-steroidolefinen mit Pb(OAC)4-n(N3)n: Studien zur erreichung einer ausgangsbasis zur gewinnung von ring-b-steroidheterocyklen

From Δ⁵-steroid olefins the seco-forms 1, 3, 7, 9, 11, 13 and 15 have been prepared using Pb(OAC)_4-n(N₃)_n as reagent. 7, 9 and 11 were transformed into the ring-B-steroid heterocycles 16 and 17 as well as 18, 19, 20 and 21 by means of catalytic hydrogenation.     

Zum verhalten von Pb(OAc)4-n(N3)n gegenüber androsta-4,9(11)-dien-3,17-dion : Pb(OAc)4-n(N3)n Als oxigenierungsmittel

An entirely new property of Pb(OAc)_4-n(N₃)_n consists in direct transfer of an O atom to the 9-,11-doublebond of the title compound with formation of the oxirane 2 and the introduction of an OH function in the allylic position at C 12 with formation of 1. In addition to the new concept,² 12α-azide 3 and the triketon 4 were also formed.     

Crystal and molecular structure of [RuNO(NO2)4OHCuPy n ] heterometallic complexes

Heterometallic complexes [RuNO(NO₂)₄OHCuPy₂(H₂O)] (I) and [RuNO(NO₂)₄OHCuPy₃] (II) are described structurally for the first time. In complex I, the ruthenium anion is coordinated to the copper atom by the bridging OH group and two bridging nitro groups; in complex II, by the bridging OH group and one bridging nitro group. Dimers are formed in the crystal lattice of complex II due to the interaction of the copper atom and the nitro group of the ruthenium anion in trans position to the bridging NO₂ group.     

Diphenyl N-halosulfilimines : Preparation,decomposition, and reactions with nucleophiles

Diphenyl N chloro (l)-N bromo (2) and N-iodo-sulfilimines (3) were prepared by halogenation of diphenyl free sulfilimine. Compound 1 decomposed in benzene at room temperature. The decomposition of 1 is a chain reaction since the reaction was induced by chlorine or t-butyl hypochlorite affording diphenyl(diphenylsulfilimino) sulfonium chloride(4a) while it was inhibited by styrene or stilbene. Compound 4a was also obtained by the reaction of 1 with diphenyl sulfide in benzene. Decomposition of 1 in acetic acid proceeded smoothly affording various products. Compound 1 reacted with sulfides sulfoxides triarylphosphines and triethylamine affording the N-substituted iminosulfonium salts. Compounds 1 and 2 were hydrolyzed with sodium hydroxide affording diphenyl sulfoximine. The reaction of 1 with sodium cyanide gave diphenyl N cyanosulfilimine(17). The reaction of 1 with Grignard reagent gave diphenyl free sulfilimine. Compounds 2 and 3 are more stable than 1. Decomposition of 2 in benzene or acetic acid gave diphenyl(diphenylsulfilimino)sulfonium perbromide(4c)     

Molecular geometry and electronic structures of stable organic derivatives of divalent germanium and tin [(\operatorname{Me} _3 \operatorname{Si} )_2 \operatorname{N} {\kern 1pt} ---{\kern 1pt} Me_2 ]_n (M = Ge, n = 1; M = Sn, n = 2): a theoretical study

The molecular geometry and electronic structure of stable organic derivatives of divalent germanium and tin, [(Me₃Si)₂N-M-OCH₂CH₂NMe₂]_n (M = Ge (4), n = 1; M = Sn (5), n =2) and their isomers with broken (4a, 5a) and closed (4b, 5b) intramolecular coordination bonds M←NMe₂, were studied by the density functional (PBE/TZ2P/SBK-JC) and NBO methods. Factors responsible for stability of their dimers 4c and 5c were established. Dimerization of 5b in the gas phase is a thermodynamically favorable process (ΔG ⁰ = ?2.1 kcal mol^?1) while that of 4b is thermally forbidden (ΔG ⁰ = 10.1 kcal mol^?1), which is consistent with experimental data. The M←NMe₂ coordination bond energies, ΔE ⁰, were found to be ?5.3 and ?8.6 kcal mol^?1 for M = Ge and Sn, respectively. NBO analysis showed that the metal atoms M in molecules 4 and 5 are weakly hybridized. The lone electron pairs of the M atoms have strong s-character while vacant orbitals of these atoms, LP* M, are represented exclusively by the metal np_z-AOs. The strongest orbital interactions between subunits in dimers 4c and 5c involve electron density donation from the lone electron pairs of oxygen atoms (LP O) to the LP* M orbitals.     

Chemoenzymatic syntheses of N-trifluoroacetyl-l-daunosamine,N-trifluoroacetyl-l-acosamine,N-benzoyl-d-acosamine,and N-benzoyl-d-ristosamine from an achiral precursor,methyl sorbate

A conjugated addition of benzylamine to methyl (4R,5S)-4,5-(isopropylidenedioxy)-(2E)-hexenoate 8a followed by lactonization under acidic condition proceeds to the formal total syntheses of l-daunosamine 4 and l-acosamine 2. On the other hand, direct conjugated addition of benzylamine to methyl (4S,5S)-4,5-epoxy-(2E)-hexenoate 5 and the subsequent intramolecular nucleophilic attack by the ester carbonyl group on the epoxy ring of the substrates leads to the formal total syntheses of d-acosamine 2 and d-ristosamine 1.     

Three new terpenoids,sterebins O,P1, and P2, isolated from Stevia rebaudiana fermented by Saccharomyces cerevisiae

The diversity of natural compounds is extensive but not unlimited. We therefore studied the feasibility of fermenting plant extracts to increase the diversity of natural compounds for use as drug candidates. Three new terpenoids, sterebins O (1), P1 (2), and P2 (3), were isolated from an extract of Stevia rebaudiana fermented by Saccharomyces cerevisiae. The structures of these compounds were established using NMR, MS, and IR methods. The absolute configuration of 1 was determined by X-ray diffraction analysis, and that of 2 and 3 from the ECD spectrum of their benzoate derivatives. These three compounds were not observed in S. rebaudiana extracts by TLC, suggesting that the compounds were generated during the fermentation process. Compounds 1, 2, and 3 all inhibited melanogenesis in theophylline-stimulated B16 melanoma cells, with 1 exhibiting the lowest IC₅₀ value (9.8 μM). The results indicate that fermentation of plant extracts may provide a route for generating many useful compounds.     

Synthesis of 12-acetoxy-1, 3-dodecadiene,an insect sex pheromone of the red bollworm moth,from a butadiene telomer

8-Phenoxy-1, 6-octadiene (1) formed by the Pd-catalyzed telomerization of butadiene with phonol was converted to 8-phenoxy-6-octen-1-ol (3). The alcohol 3 was converted to 8-iodo-1-phenoxy-2-octene (5). The Grignard reagent 7 prepared from 4-chloro 1-butyl tetrahydropranyl ether was coupled with the iodide 5 by the catalysis of CuI and bipyridyl to give 12-phenoxy-10-dodecen-1-ol (9), which was converted to 12-acetoxy-1-phenoxy-2-dodecene (10). Finally, 12-acetoxy-1, 3-dodecadiene (11) was obtained by the palladium catalyzed elimination of phenol from phenoxyacetoxy-dodecene (10).