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1.
Manfred Braun 《Tetrahedron letters》1979,20(31):2885-2888
A new synthesis of the naturally occurring anthraquinones catenarin () and erythroglaucin () involves regioselective addition of to the anhydride . 相似文献
2.
The photochemical reactions of tetracyclic azo compounds () giving and via diazoethane derivatives () were investigated in addition to the nitrogen extrusion reactions leading to tetracyclo[4.3.0.02,9.05,7nonenes (). 相似文献
3.
A stereoselective synthesis of the known synthetic intermediate () for (-)-carpetimycin a () has been achieved starting from the monocyclic β-lactcon () by the novel use of the direct aldol condensation of with acetone via the titaniun enolate. 相似文献
4.
Miyoji Hanaoka Shingo Yasuda Kazuyoshi Nagami Keiko Okajima Takeshi Imanishi 《Tetrahedron letters》1979,20(39):3749-3752
Irradiation of the berberinephenolbetaines (, , and ) effected valence tautomerization to give the 8,14-cycloberbines (, , and ), the aziridine derivatives, in high yield. The 8,14-cycloberbines were efficiently converted to the spirobenzylisoquinolines by regioselective C bond cleavage. 相似文献
5.
Nb-oxides and in the presence of acetic anhydride led to products , or with participation of the indole nucleus during the fragmentation reaction. 相似文献
6.
Condensation of 3-fluoro-2-butanone () with alkyl diethylphosphonoacetates () gave alkyl 4-fluoro-3-methyl-2-pentenoates (). Addition of bromine yielded alkyl-2,3-dibromo-4-fluoro-3-methylpentanoates () which were dehydrobrominated to alkyl 2-bromo-4-fluoro-3-methyl-2- pentenoates (). Since these compounds could not be hydrogenated to the desired alkyl 2-bromo-4-fluoro-3-methylpentanoates (), another route was taken. The esters were hydrogenated to alkyl 4-fluoro-3- methylpentanoates () which were converted to their carbanions. Treatment with bromine gave esters , and iodine gave alkyl 4-fluoro-2-iodo- 3-methylpentanoates (). Esters and were converted to alkyl 2-azido-4-fluoro-3-methylpentanoates () whose hydrogenation gave alkyl 2-amino-4-fluoro-3-methylpentanoates (). Hydrolysis afforded γ-fluoroisoleucine (). 相似文献
7.
Wolfgang Oppolzer Samuel Siles Roger L. Snowden Bartholomeus H. Bakker Martin Petrzilka 《Tetrahedron letters》1979,20(45):4391-4394
The opposite regiochemistry, observed for the reactions → and → , as compared with additions → , → and → , supports the hypothesis that in the transition state of nitrone-olefin additions the new C,C bond is more advanced than the C,0, bond. Further examples show the superimposition of substituent effects on this intramolecular control. 相似文献
8.
The regiospecific synthesis of an established 11-desoxyanthracycline synthon () from aloe-emodin () is described. 相似文献
9.
The vinylbromides and are allowed to react ith AgBF4 and AgPF6 in the presence of various olefins in CH2Cl2 as the solvent. Except for the reaction of cyclopentene with all other olefins used, react with vinyl cation to form the cycloaddition products , and in high yields. 相似文献
10.
The cationic cyclization of the carbinol (Z) occurred stereoselectively and resulted in a mixture of the hydrindane and the octalin , both with configuration of side chain and angular methyl group. Cyclization of (E) yielded in and , both with -configuration. The structure of , was proved by transformation to the diketones ,. 相似文献
11.
Junzo Nokami Toshio Ono Shoji Wakabayashi Atsuo Hazato Seizi Kurozumi 《Tetrahedron letters》1985,26(16):1985-1988
PGJ2 analogues, the title compound () and its related derivatives (, ), were synthesized the three-component coupling process involving 1,4-addition reaction of phenylsulfinylallylic carbanion (′) to cyclopentenone derivative () followed by trapping the generated enolate with aldehyde (). 相似文献
12.
The ketol and its acetate when refluxed in methanolic potassium hydroxide (5%) were found to rearrange to 4-methyl-8-acetyl-5,6,7,8-tetrahydro-1-naphthol . The epimeric acetate also behaved likewise. A mechanism is suggested for the rearrangement. 相似文献
13.
《Tetrahedron letters》1986,27(19):2117-2120
Highly stereoselective addition of Grignard reagents to chiral open-chain α,-ketoacetals (,) has been attained. Application of the reaction to syntheses of the key intermediates (,) for (R)- and (S)-mevalolactone is also described. 相似文献
14.
New tetracyclic derivatives (3a,, 5, 8) similar to protoberberines, but containing a lactam structural element and other hetero atoms besides the bridge-head nitrogen in rings B and C, were prepared by cycloaddition of 6,7-dimethoxy-2H-1,3-benzothiazine (1a) with -substituted aromatic carboxylic acid derivatives (2a,, 4) and from 4- methyl-6,7-dimethoxy-2-1,3-benzothiazine (1b) with 3.5-dinitrobenzoyl chloride. 相似文献
15.
Reduction of the racemic α-hydroxy ketones((±)-) with fermenting baker's yeast followed by fractional recrystallization and oxidation was found to readily afford optically pure anthracyclinone intermediates((R) (?)- and their partially optically active antipodes ((S)(+)-). The useless enantiomers ((S)(+)- and diastereomeric -diols((+)- ) could be recycled to (±)- and the achiral ketones() by racemization and oxidative cleavage, respectively. 相似文献
16.
Through the insertion of a carbon dioxide molecule, the oxazolidin-2-ones () and () were prepared by treataent of the salts () and () with carbonate anion on polymeric support. The hydrolysis under basic conditions of () and () afforded the erythro-3-amino-1,2-diols () and () which were fully acetylated: the 2-amino-2-deoxyerythritol derivative () was obtained in 91% yield. 相似文献
17.
Photochemical rearrangements of 2,5-cyclohexadienones and to bridged triazenes and zwitterions and are described. 相似文献
18.
Treatment of , , and with methyllithium affords , ; , ; and respectively in serviceable yields carbenoid cyclization. 相似文献
19.
Yasuo Sakai Shingo Toyotani Yoshito Tobe Yoshinobu Odaira 《Tetrahedron letters》1979,20(40):3855-3856
Oxidative decarboxylation of [n.2.2]propellane carboxylic acids (-) with lead tetraacetate gave the bicyclic acetates (, ) having a bridgehead double bond and/or the tricyclic acetates (, ) in good yields. Vapor phase thermolysis of or afforded the bridgehead olefin or quantatively. 相似文献
20.
I.T. Chizhevsky N.V. Rastova N.E. Kolobova F.V. Petrovskii L.E. Vinogradova L.A. Leites 《Tetrahedron letters》1985,26(30):3605-3608
Cationic hydroxyallylolefin π-complexes whose stabilization of the α-carbocationic centre is achieved with simultaneous participation of both rhodium and oxygen atoms were prepared from the reaction of HCl or F2POOH with aldehyde in ether. 相似文献