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1.
Several π-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods. The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls , and . Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction. The second method,which consists of the Ni-or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides,has been used to prepare the bi-aryls , which contain two heteroaromatic units, and the ter-aryl . Compound has been also prepared starting from 2-(2-thienyl) furan () by selective lithiation, followed by bromination.The 13C NMR signals of and have been assigned on the basis of the literature data and by relaxation measurements. Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls , and the ter-aryls . 相似文献
2.
《Tetrahedron》1987,43(15):3471-3480
Biologically inactive but easily available chaparrin has been converted into potent antileukemic C-15 esters of glaucarubolone and quassinoid analogs in which the C-15 ester side chain has been replaced by an alkyl or alkenyl group.The synthetic methodology developed has been applied to the preparation of C-15 ester derivatives , , and quassinoid analogs , and . 相似文献
3.
Natural (?)-botryodiplodin() has been synthesized from an antibiotic methylenomycin A (). The absolute configurations of (?)-botryodiplodin( and methylenomycin A () have also been established as shown in and respectively. 相似文献
4.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
5.
Reaction of ,,,-[9]annulene anion () with electrophiles (-) leads to substituted ,,,-1,3,5,7-cyclononatetraenes (-) which are precursors for the preparation of 10- and 10,10′-donor-substituted nonafulvenes (e.g. ). The influence of solvent and temperature on the 1H-nmr spectra of the nonafulvenes - has been investigated. 相似文献
6.
Mohammad A. Hai Nigel W. Preston Henri-Philippe Hussont Christiane Kan-Fan Ralph C. Bick 《Tetrahedron》1984,40(21):4359-4361
The structure of the Aristorelia alkaloid aristoserratenine () has been determined by spectroscopic means, and confirmed by rearrangement to aristoteline (). The structure of tasmanine () has been confirmed similarly, and the configuration at the spiro carbon of each base has been determined by nOe experiments. 相似文献
7.
Thermal dimerisation of 3,4-epoxyprecocene II () in absence of solvents afforded high yields (65%) of tetrahydrofuran dimer and minor amounts of benzopyran-3-one . On the other hand, two new dimers, γ-hydroxyketone and dioxane have also been isolated from treatment of with different acids. Structural elucidations for all these dimers have been carried out by spectroscopic and analytical methods, combined with the use of selected deuteriated precursors in the corresponding dimerisation procedures. 相似文献
8.
A stereospecific synthesis of acetyl--valyl-detoxininolactone has been performed and the absolute stereochemistry of detoxinine has been revised to (2, 3, 1′)-2-(2′-carboxy-1′-hydroxyethyl)-3-hydroxypyrrolidine. 相似文献
9.
Shosuke Yamamura Seiji Kosemura Shigeru Ohba Masatoki Ito Yoshihiko Saito 《Tetrahedron letters》1981,22(52):5315-5318
Two new toxic substances, euphoscopins A and B, have been isolated from the plant L., and their absolute stereostructures also been elucidated on the basis of their spectral data coupled with an X-ray crystallographic analysis of the -bromobenzoate readily obtained on treatment of euphoscopin A with -bromobenzoyl chloride - pyridine. These antitumor substances belong to a group of jatrophone-type diterpenes. 相似文献
10.
Novel bis(perhaloalkyl) pentathiodipercarbonates have been synthesized by reaction of sulfenyl chlorides with metal trithiocarbonates, and the heptathio analog was prepared similarly. Lenthionine is the main product when diiodomethane is treated with sodium tetrathiopercarbonate. A rearrangement of bis(alkyldithio)chloromethanesulfenyl chlorides to alkyldithio) (alkyltrithio)dichloromethanes has been observed. Additions of sulfenyl chlorides and of thiosulfenyl chlorides to the thiocarbonyl compounds and were achieved in acetonitrile. The structures of the first crystalline pentathiodipercarbonate and α,α,α-tris(disulfide) , and of the first reported α,α,α-tris(trisulfide) have been determined by X-ray crystallography. 相似文献
11.
Alkylation of the distal double bond of pseudoionone has been carried out with isoprene epoxide (ZnCl2 /MeNO2 ) leading directly to α-, α- and γ hydroxyprenylionones. The α- and γ-isomers have been converted in few steps into the C50 carotenoids decaprenoxanthin and C.p. 450 respectively. 相似文献
12.
Inactive chaparrin has been converted in seven steps and in 16% overall yield to castelanone which is known to inhibit significantly growth of the murine lymphocytic leukemia P-388 cell line. The methodology developed has been applied to the preparation of quassinoid analogs , and . 相似文献
13.
Alireza Hoorfar W. David Ollis J. Fraser Stoddart David J. Williams 《Tetrahedron letters》1980,21(43):4211-4214
The tetra-anthranilide derivatives ()–() have been synthesised. X-Ray crystallography shows that ,′,″-trimethyltetra-anthranilide () adopts a conformation with three - and one -amide linkages in the solid state. Dynamic 1H n.m.r. spectroscopy indicates that -benzyl-′,″,′″-trimethyltetra-anthranilide () exists as an interconverting ternary mixture of chiral non-planar conformational diastereoisomers in solution. 相似文献
14.
11-Deoxyanthracyclinone precursors and have been prepared regiospecifically by the reaction of bromojuglone methyl ethers and with vinylketene acetal , prepared from the Hagemann's ester ketal . 相似文献
15.
John A. Edgar Nigel J. Eggers Alan J. Jones Graeme B. Russell 《Tetrahedron letters》1980,21(27):2657-2660
A series of 14-membered ring macrocyclic pyrrolizidine alkaloids have been isolated from and . 相似文献
16.
Mahmoud Al-Talib Ibrahim Jibril Johannes C. Jochims Gottfried Hunter 《Tetrahedron》1985,41(3):527-536
2-Azaallenium salts react with diisopropyl carbodiimide to afford the formal dihydro-1,3-diazetium salts . The structure of has been confirmed by an X-ray diffraction analysis. With the carbodiimide the tetraphenyl-2-azaallenium salt reacts to give the guanidinium compound .The diazetium salts react with further carbodiimide to afford the formal 2-azaallenium salts . With tert-butyl isocyanide the 2-azaallenium salts undergo an Ugi reaction to yield the nitriles . 相似文献
17.
Subodh Bhatnagar Judith Polonsky Marc Vuilhorgne Thierry Prangé Claudine Pascard 《Tetrahedron letters》1982,23(49):5159-5162
Laurycolactone A and B are new quassinoids with a C18 basic skeleton isolated from the Vietnamese Simaroubaceae, Eurycoma longifolia Jack. The structure of Eurycomalactone, a C19 quassinoid isolated previously from the same plant, has been revised and shown to be . The structures have been established by spectral means and those of and confirmed by X-ray diffraction analysis. 相似文献
18.
Philip Warner Suae-Chen Chang Douglas R. Powell Robert A. Jacobson 《Tetrahedron letters》1981,22(6):533-536
The carbonic dimers of some tricyclic cyclopropylidenoids have been isolated. The X-ray structure of one () has been determined. These are derivatives of tetra--butylethylene (). 相似文献
19.
G. Bruce Guise W. David Ollis Judith A. Peacock Julia Stephanidou Stephanatou J. Fraser Stoddart 《Tetrahedron letters》1980,21(43):4203-4206
The trithiosalicylide derivatives () - () have been synthesised and shown to exist in solution as ring inverting (?*) enantiomeric helical conformations. 相似文献
20.
Simon J. Edge W.David Ollis Julia Stephanidou Stephanatou J.Eraser Stoddart David J. Williams Kwamena A. Woode 《Tetrahedron letters》1981,22(23):2229-2232
The tri-3-methyltrianthranilide derivatives ()–() have been synthesised. Dynamic 1H n.m.r. spectroscopy indicates that the ,′,″-trimethyl derivative () exists in solution as slowly ring inverting ( ? *) enantiomeric helical conformations. X-Ray crystallography shows that the ,′-dimethyl-″-benzyl derivative () undergoes spontaneous resolution when it crystallises as a 1:1 adduct from toluene. The host molecules adopt a helical conformation (Figure 1) within a lattice structure that contains chiral channels (Figure 2) occupied by guest solvent molecules. 相似文献