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1.
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
2.
Herbert Muffler Guenter Siegemund Werner Schwertfeger 《Journal of fluorine chemistry》1982,21(2):107-132
4.5-Perfluoro-1.3-dioxolanes are available by reaction of 2(α-chloroalkoxy)perfluoro-carbonyl halides or -ketone with fluoride ions. A mechanism for the intramolecular ring- closure-reaction is proposed. Hydrogen atoms at C-2 in can be exchanged photochemically by chlorine. Starting from the 2-monochloro-derivatives the 2-monofluoro-4.5-perfluoro- 1.3-dioxolanes are formed by reaction with triethylamine- hydrofluoride. 相似文献
3.
T. Tanaka N. Okamura K. Bannai A. Hazato S. Sugiura K. Manabe S. Kurozumi 《Tetrahedron letters》1985,26(45):5575-5578
(5)-Prostaglandin E2 methyl ester was synthesized from ()-4--butyldimethylsiloxy-2-cyclopentenone by 2-alkenyloxycarbonylation of the organocopper conjugate-addition adduct followed by intramolecular palladium-catalyzed decarboxylative 2-alkenylation. A ()-2-butenylated cyclopentanone derivative was obtained from either 2-[()- or ()-2-butenyloxy-carbonyl]cyclopentanone derivative under the similar reaction condition. 相似文献
4.
3,4-Tetramethylene- and -3,4-diethyl-1,2-dioxetane ( and ) were prepared and characterized (for - Ea = 22.5 kcal/mole, log A = 12.8; for - Ea = 24.5 kcal/mole, log A = 13.1). 相似文献
5.
A new and convenient synthesis of 2-isopropylfuro-(2,3-b)quinolines () from 3-(3-methylbut-1-enyl)-2-quinolones () is described. A neat synthesis of the alkaloids (±)-lunacrine (), (±)-lunasine () and (±)-demethoxylunacrine () is also reported. 相似文献
6.
The new building blocks , , and have been effecively synthesized starting from 2-hydroxymethyl-4-phenylthio-1-butene (). A convenient synthesis of retinoic acid methyl ester () using is also described. 相似文献
7.
A simple preparation of 2-carbomethoxy-2-azabicyclo[3.3.1]nonan-6-one ( and its conversion to the racemic benzomorphans: , , are described. 相似文献
8.
Yitzhak Apeloig Dorit Arad Dieter Lenoir Paul Von Ragué Schleyer 《Tetrahedron letters》1981,22(9):879-882
A 5-cyano substituent decelerates the solvolysis rate of exo-2-norbornyl brosylate by a factor of 1790. A much smaller deceleration (24–90 fold) is observed for the secondary and for both and tertiary 2-norbornyl derivatives. These results support the occurrence of σ-participation in the solvolysis of . 相似文献
9.
Eiichi Kitazawa Akira Ogiso Shuji Takahashi Masaaki Kurabayashi Harumitsu Kuwano Tadashi Hata Chihiro Tamura 《Tetrahedron letters》1979,20(13):1117-1120
Two new diterpenelactones named plaunol A () and B () exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, . Structure of was determined by X-ray analysis of its -bromobenzoate and structure of was deduced from the results of chemical correlation and the spectral data. 相似文献
10.
Kanzo Sakata Hajime Masago Akira Sakurai Nobutaka Takahashi 《Tetrahedron letters》1982,23(20):2095-2098
A very unusual dithiokikeptopiperazine structure () has been assigned to aspiroclorine, C9H12N2O5S2Cl, produced as a biologically active substance together with canadensolide by , which has been found to be identical with the antibiotic A 30641 from . 相似文献
11.
A general route for synthesis of 6--alkyl-2∝deoxyguanosine nucleosides is described. The key step is conversion of the 6--TPS derivative to the 6-trimethylamino compound . The trimethylamino group is readily displaced by alcohols in the presence of DBU. Using this route the 6--methyl, ethyl and n-butyl 2∝-deoxyguanosine derivatives have been prepared in excellent overall yields. 相似文献
12.
A sequence of formylation followed by a carbene insertion reaction has led to the stepwise introduction of additional ethano bridges into 4,5,7,8- tetramethyl [22](1,4)cyclophane (), providing syntheses of 5,7,8-trimethyl- [23](l,2,4)cyclophane (), a mixture of 5,8-dimethyl[24(1,2,4,5)cyclophane () and 5,7-dimethyl[24(1,2,3,5)cyclophane (, and-4-methyl[25](1,2,3,4,5)-cyclophane (). This route to completes a formal eight-step synthesis of [26](1,2,3,4,5,6)cyclophane (, superphane) with an overall yield of 17%. A Birch reduction of readily gave 12,15-dihydro-5,7,8-trimethyl[23](1,2,4)-cyclophane () in 85% yield. 相似文献
13.
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
14.
A proton nmr follow-up provided conclusive evidence for the involvement of two sequential Claisen rearrangements in the thermal rearrangement of 1,4-diaryloxy-2-butynes to 11a-methylpterocarpans . A detailed study of the rearrangement of 1,4-diaryloxy-2-butynes in polyethyleneglycol-200 (PEG-200), indicated a definite possibility of selective synthesis of either benzofuron (3,2-b )benzofuran or benzofuro(2,3-b)benzofuran by varying the temperature of the reaction alone 相似文献
15.
A short-step synthesis of , the right-hand half of antibiotic saframycin (), is described. The key steps of this synthesis are the acid catalyzed intramolecular double cyclization of and the oxidative demethylation of to the quinone (). 相似文献
16.
With the aid of nanosecond laser flash photolysis OH is chemically produced and observed “collision free”. The rotational states show inverted population in the A doublets J = , , , and of 2Π and anti-i higher rotational states. The intensities of the main and satellite absorption lines further indicate an inversion in special hyperfine states. Application to interstellar OH maser emission is considered. 相似文献
17.
The conversion of quadricyclane () to norbornadiene () is catalyzed by stannous chloride and stannous chloride-phosphine complexes. A newly synthesized polymer-bound phosphine-stannous chloride complex also proved effective in the catalytic conversion of to . 相似文献
18.
Biogenetic-type synthesis of (±)-dictyopterene A () was achieved employing 1,-5-undecadien-3-ol () postulated to be a biosynthetic intermediate of : this synthesis means that transformation of dictyoprolene () into dictyopterene A () was formally made. 相似文献
19.
A new backbone rearrangement is observed in A/B methyl lithocholate derivatives. It is initiated from the C-3 carbon either by dehalogenation of the chloroesters by AgSbFg6 or by the action of the triflic anhydride on the si1y1ated ether . This rearrangement leads to methyl diacholenate and new lactones in D-homoandrostane series and . The differences of behaviour between A/B and A/B series and the mechanism of rearrangements are discussed. 相似文献
20.
The biosynthesis of the tetrahydroanthraquinone, altersolanol A (), by has been established by the incorporation of [1,2-13C2]-acetate. A blocked culture of was utilized to reveal that is metabolized to altersolanol B and macrosporin. 相似文献