Four new 9,10‐secocycloartane (=9,19‐cyclo‐9,10‐secolanostane) triterpenoidal saponins, named huangqiyenins G–J ( 1 – 4 , resp.), were isolated from Astragalus membranaceus Bunge leaves. The acid hydrolysis of 1 – 4 with 1M aqueous HCl yielded D ‐glucose, which was identified by GC analysis after treatment with L ‐cysteine methyl ester hydrochloride. The structures of 1 – 4 were established by detailed spectroscopic analysis as (3β,6α,10α,16β,24E)‐3,6‐bis(acetyloxy)‐10,16‐dihydroxy‐12‐oxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 1 ), (3β,6a,10α,24E)‐3,6‐bis(acetyloxy)‐10‐hydroxy‐12,16‐dioxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 2 ), (3β,6α,9α,10α,16β,24E)‐3,6‐bis(acetyloxy)‐9,10,16‐trihydroxy‐9,19‐cyclo‐9,10‐secolanosta‐11,24‐dien‐26‐yl β‐D ‐glucopyranoside ( 3 ), and (3β,6α,10α,24E)‐3,6‐bis(acetyloxy)‐10‐hydroxy‐16‐oxo‐9,19‐cyclo‐9,10‐secolanosta‐9(11),24‐dien‐26‐yl β‐D ‐glucopyranoside ( 4 ). 相似文献
Binary blends of poly(2,6–dimethyl–1,4–phenylene oxide) (PPE) with various styrene copolymers were investigated. Poly(styrene–co–acrylonitrile) (SAN), poly[styrene–co–(methyl methacrylate)] (SMMA), poly[styrene–co–(acrylic acid)] (SAA) and poly[styrene–co–(maleic anhydride)] (SMA) are only miscible with PPE when the amount of comonomer is rather small. From calculated binary interaction densities it can be concluded that the strong repulsion between PPE and comonomer limits miscibility. In blends of PPE with SAN, as well as with ABS, the inter-facial tension between the blend components is significantly reduced upon addition of polystyrene–block–poly–(methyl methacrylate) diblock copolymers (PS–b–PMMA) and polystyrene–block–poly (ethylene–co–butylene)–block–poly–(methyl methacrylate) triblock copolymers (PS–b–PEB–b–PMMA). They show a profound influence on morphology, phase adhesion and mechanical blend properties. 相似文献
Two novel compounds, 8–[2–(2–thienyl)vinyl]–10,10–dimethyl–10H–pyrido[1,2–a] indolium perchlorate ( 3a ) and 8–[2–(5–phenyl–2–thienyl)vinyl]–10,10–dimethyl–10H–pyrido[1,2–a]indolium perchlorate ( 3b ) were synthesized and characterized by IR, 1H–NMR, elemental analyses, and X–ray diffraction. Crystal structural analysis suggested that either 3a or 3b exhibited good coplanarity and rings and vinyl in the target molecule could make up a large conjugated system. Ultraviolet–visible absorption analysis indicated both 3a and 3b possessed large maximum absorptions, and 3b underwent a significant redshift (43.0 nm) in comparison with 3a . 相似文献
Building bridges : The title compound forms an unprecedented polymeric structure with bridging B–H–B three‐center two‐electron bonds in the solid state. This organoborane serves as an efficient precursor for the preparation of boron‐doped π‐conjugated polymers by hydroboration polymerization with a functionalized 1,4‐diethynylbenzene (see picture). These polymers form thin films that show intense green luminescence.
Bioactivity‐guided isolation of the rare gorgonian Muricella sibogae (Nutting ) yielded the two new eunicellin diterpenes sibogin A and B ( 1 and 2 ), the three new 9,10‐secosteroids sibogol A–C ( 6 – 8 ), together with the three known eunicellin diterpenes 3 – 5 and the five known 9,10‐secosteroids 9 – 13 . Their structures were established by extensive spectral analysis (1D‐ and 2D‐NMR, IR, and MS). The cytotoxicity of the isolates 1 – 13 was evaluated in vitro against the selected tumor cell lines P388 and BEL‐7402. All the compounds showed only weak activity against P388 cell lines, with an inhibition rate ranging from 10 to 60% at a concentration of 50 μg/ml, whereas the were inactive against BEL‐7402 cell lines. 相似文献
The syntheses of the zwitterionic spirocyclic λ5Si-silicates 6–9 are described. These chiral zwitterions contain a pentacoordinate (formally negatively charged) silicon atom and a tetracoordinate (formally positively charged) nitrogen atom. Compounds 6 · 1/2 HO(CH2)2OH, 7 , 8 · CH3CN, and 9 were studied by solution-state (1H, 13C, 29Si) and solid-state (29Si CP/MAS) NMR experiments. In addition, all compounds were structurally characterized by single-crystal X-ray diffraction. The dynamic behavior (Berry-type enantiomerization) of 7–9 in solution was studied by VT 1H NMR experiments. These experimental studies were completed by ab initio investigations of the related anionic model species 10–12 . 相似文献
The ‘click synthesis’ of some novel O‐substituted oximes, 7a – 7t , which contain 1,2,3‐triazolediyl residues, as new analogs of β‐adrenoceptor antagonists is described (Schemes 1–4). The synthesis of these compounds was achieved in four to five steps. The formation of oximes of 9H‐fluoren‐9‐one and benzophenone, i.e., 9a and 9b , respectively, followed by their reaction with propargyl bromide, afforded O‐propargyl oximes 10a and 10b , respectively, which by a subsequent CuI‐catalyzed Huisgen cycloaddition with prepared β‐azido alcohols 11a – 11j (Schemes 2 and 3), led to the target compounds 7a – 7t in good yields. 相似文献
In the crystal structure of the l ‐His–cIMP complex, i.e.l ‐histidinium inosine 3′:5′‐cyclic phosphate [systematic name: 5‐(2‐amino‐2‐carboxyethyl)‐1H‐imidazol‐3‐ium 7‐hydroxy‐2‐oxo‐6‐(6‐oxo‐6,9‐dihydro‐1H‐purin‐9‐yl)‐4a,6,7,7a‐tetrahydro‐4H‐1,3,5,2λ5‐furo[3,2‐d][1,3,2λ5]dioxaphosphinin‐2‐olate], C6H10N3O2+·C10H10N4O7P−, the Hoogsteen edge of the hypoxanthine (Hyp) base of cIMP and the Hyp face are engaged in specific amino acid–nucleotide (His...cIMP) recognition, i.e. by abutting edge‐to‐edge and by π–π stacking, respectively. The Watson–Crick edge of Hyp and the cIMP phosphate group play a role in nonspecific His...cIMP contacts. The interactions between the cIMP anions (anti/C3′–endo/trans–gauche/chair conformers) are realized mainly between riboses and phosphate groups. The results for this l ‐His–cIMP complex, compared with those for the previously reported solvated l ‐His–IMP crystal structure, indicate a different nature of amino acid–nucleotide recognition and interactions upon the 3′:5′‐cyclization of the nucleotide phosphate group. 相似文献
Boron trifluoride reacted with dipyrid-2-ylamine 6 , its N-methyl and 6,6′-dimethyl derivatives 8 and 10 , and 3,3′,5,5′-tetraphenyl-6-azapyrromethene 13 to give fluorescent β-azavinamidine (1,3,5-triazapenta-1,3-diene) dyes: 10-azapyridomethene–BF2 complex 5 (λf 422 nm, λlas 426 nm), its quaternary 10-methyl tetrafluoroborate and 4,6-dimethyl derivatives 9 (λf 362 nm) and 11 (λf 416 nm), and 1,3,5,7-tetraphenyl-8-azapyrromethene–BF2 complex 17 (λf 696 nm). Treating 3,3′,4,4′-tetraphenyl-5,5′,6-trimethylpyrromethene (prepared in situ from ethyl 3,4-diphenyl-5-methylpyrrole-2-carboxylate in a reaction with acetyl chloride) with boron trifluoride gave 1,2,6,7-tetraphenyl-3,5,8-trimethylpyrromethene–BF2 complex 21 . Absorption for the vinamidine chromophore differed from that for the β-azavinamidine chromophore by a hypsochromic shift of 86 nm in a comparison of pyridomethene–BF2 complex 3 with its 10-aza derivative 5 and by a bathochromic shift of 105 nm in a comparison of the pyrromethene–BF2 complex 20 with the 8-azapyrromethene–BF2 complex 17 . 相似文献
The reaction of 9,10‐dibromo‐9,10‐dihydro‐9,10‐diboraanthracene (9,10‐dibromo‐DBA, 3 ) with two equivalents of 9‐lithio‐2,6‐ or 9‐lithio‐2,7‐di‐tert‐butylanthracene gave the corresponding 9,10‐dianthryl‐DBAs featuring two ( 4 ) or four ( 5 ) inward‐pointing tert‐butyl groups. Compound 4 exists as two atropisomers, 4 and 4′ , due to hindered rotation about the exocyclic B? C bonds. X‐ray crystallography of 5 suggests that the overall interactions between facing tert‐butyl groups are attractive rather than repulsive. Even in solution, 4 / 4′ and 5 are stable toward air and moisture for several hours. Treatment of 3 with 10‐lithio‐9‐R‐2,7‐di‐tert‐butylanthracenes carrying phenyl (R=Ph), dimesitylboryl (R=Mes2B), or N,N‐di(p‐tolyl)amino (R=Tol2N) groups gave the corresponding 9,10‐dianthryl‐DBA derivatives 9 – 11 in moderate to good yields. In these molecules, all four solubilizing tert‐butyl groups are outward pointing. The solid‐state structures of 4 , 5 , 9 , and 10 reveal twisted conformations about the exocyclic B? C bonds with dihedral angles of 70–90°. A significant electron‐withdrawing character was proven for the Mes2B moiety, but no appreciable +M effect was evident for Tol2N. Compounds 5 , 9 , and 11 show two reversible DBA‐centered reduction waves in the cyclic voltammogram. In the case of 10 , a third reversible redox transition can be assigned to the Mes2B–anthryl substituents. The UV/Vis absorption spectrum of 5 is characterized by a very broad band at λmax=510 nm, attributable to a twisted intramolecular charge‐transfer interaction from the anthryl donors to the DBA acceptor. The corresponding emission band shows pronounced positive solvatochromism (λem=567 nm, C6H12; 680 nm, CH2Cl2) in line with a highly polar excited state. The charge‐transfer bands of 10 and 11 , as well as the emission bands of 9 and 10 , are redshifted relative to those of 5 . The Tol2N derivative 11 is essentially nonfluorescent in solution, but emits bright wine‐red light in the solid state. 相似文献
2,3,6,7‐Tetrahydroxy‐9,10‐dimethyl‐9,10‐dihydro‐9,10‐ethanoanthracene crystallizes with 1,4‐dioxane to give a bis‐solvate, C18H18O4·2C4H8O2. The bis(catechol) molecule is located on a twofold axis and the two aromatic rings form a dihedral angle of 130.61 (4)°. Hydrogen bonds are formed between the hydroxyl groups and either a neighbouring bis(catechol) molecule or the ether‐O atom of a dioxane molecule. 相似文献
The new compounds Pr8(C2)4Cl5 (1), Pr14(C2)7Cl9 (2), Pr22(C2)11Cl14 (3), Ce2(C2)Cl (4), La2(C2)Br (5), Ce2(C2)Br (6), Pr2(C2)Br (7), Ce18(C2)9Cl11 (8), and Ce26(C2)13Cl16 (9) were prepared by heating mixtures of LnX3, Ln and carbon or in an alternatively way LnX3, and “Ln2C3–x” in appropriate amounts for several days between 750 and 1200 °C. The crystal structures were investigated by X‐ray powder analysis (5–7) and/or single crystal diffraction (1–4, 8, 9). Pr8(C2)4Cl5 crystallizes in space group P21/c with the lattice parameters a = 7.6169(12), b = 16.689(2), c = 6.7688(2) Å, β = 103.94(1) °, Pr14(C2)7Cl9 in Pc with a = 7.6134(15), b = 29.432(6), c = 6.7705(14) Å, β = 104.00(3) °, Pr22(C2)11Cl14 in P21/c with a = 7.612(2), b = 46.127(9), c = 6.761(1) Å, β = 103.92(3) °, Ce2(C2)2Cl in C2/c with a = 14.573(3), b = 4.129(1), c = 6.696(1) Å, β = 101.37(3) °, La2(C2)2Br in C2/c with a = 15.313(5), b = 4.193(2), c = 6.842(2) Å, β = 100.53(3) °, Ce2(C2)2Br in C2/c with a = 15.120(3), b = 4.179(1), c = 6.743(2) Å, β = 101.09(3) °, Pr2(C2)2Br in C2/c with a = 15.054(5), b = 4.139(1), c = 6.713(3) Å, β = 101.08(3) °, Ce18(C2)9Cl11 in P$\bar{1}$ with a = 6.7705(14), b = 7.6573(15), c = 18.980(4) Å,α = 88.90(3) °, β = 80.32(3) °, γ = 76.09(3) °, and Ce26(C2)13Cl16 in P21/c with a = 7.6644(15), b = 54.249(11), c = 6.7956(14) Å, β = 103.98(3) ° The crystal structures are composed of Ln octahedra centered by C2 dumbbells. Such Ln6(C2)‐octahedra are condensed into chains which are joined into undulated sheets. In compounds 1–4 three and four up and down inclined ribbons alternate (4+4–, 4+3–3+4–, 4+4–3+4–4+3–), in compounds 8 and 9 four and five (4+5–, 5+4–4+5–4+4–), and in compounds 4–7 one, one ribbons (1+1–) are present. The Ln‐(C2)‐Ln layers are separated by monolayers of X atoms. 相似文献
Six new compounds, phochinenins A–F ( 1 – 6 ), dimerized from 9,10‐dihydrophenanthrene and dihydrostilbene through direct coupling or an oxygen bridge, along with eight known compounds, were isolated from the whole plants of Pholidota chinensis. Their structures were elucidated on the basis of extensive spectroscopic investigations (1D‐, 2D‐NMR, and HR‐EI‐MS). 相似文献
9,10‐Diphenyl‐9,10‐epidioxyanthracene, C26H18O2, (I), was accidentally used in a photooxygenation reaction that produced 9,10‐dihydro‐10,10‐dimethoxy‐9‐phenylanthracen‐9‐ol, C22H20O3, (II). In both compounds, the phenyl rings are approximately orthogonal to the anthracene moiety. The conformation of the anthracene moiety differs as a result of substitution. Intramolecular C—H⃛O interactions in (I) form two approximately planar S(5) rings in each of the two crystallographically independent molecules. The packing of (I) and (II) consists of molecular dimers stabilized by C—H⃛O interactions and of molecular chains stabilized by O—H⃛O interactions, respectively. 相似文献
In the presence of water, benzene‐1,4‐diboronic acid (1,4‐bdba) and 4,4′‐bipyridine (4,4′‐bpy) form a cocrystal of composition (1,4‐bdba)(4,4′‐bpy)2(H2O)2, in which the molecular components are organized in two, so far unknown, cyclophane‐type hydrogen‐bonding patterns. The asymmetric unit of the title compound, C6H8B2O4·2C10H8N2·2H2O, contains two 4,4′‐bpy, two water molecules and two halves of 1,4‐bdba molecules arranged around crystallographic inversion centers. The occurrence of O—H...O and O—H...N hydrogen bonds involving the water molecules and all O atoms of boronic acid gives rise to a two‐dimensional hydrogen‐bonded layer structure that develops parallel to the (01) plane. This supramolecular organization is reinforced by π–π interactions between symmetry‐related 4,4′‐bpy molecules. 相似文献