共查询到20条相似文献,搜索用时 911 毫秒
1.
Koichi Hirai Katsumi Fujimoto Yuji Iwano Tetsuo Hiraoka Tadashi Hata Chihiro Tamura 《Tetrahedron letters》1981,22(11):1021-1024
The Δ1-carbapenem derivative() was prepared by the aldol condensation of the dialdehydic compound() with piperidinium acetate. Careful hydride reduction followed by benzoylation gave b, which was successfully decarbalkoxylated to . The X-ray structure analysis of showed the C-3 carboxylate group and C-5 H are each other. 相似文献
2.
Oxidation of palmatine () choride with -chloroperbenzoic acid in methylene chloride in the presence of sodium bicarbonate at near ?78° C yields polycarpine (). A new biogenetic route to the aporphines is proposed which does not involve phenolic oxidative coupling, and proceeds through the intermediacy of protoberberinium salts. 相似文献
3.
A short, stereoselective synthesis of (±)-warburganal (), its C-9 epimer () and the related sesquiterpene dialdehyde (±)-isotadeonal is presented. 相似文献
4.
produces the new dimer kalashine (), together with the previously reported pakistanamine () and pakistanine (). Kalashine is the first aporphine-benzylisoquinoline known to be substituted at C-11. Acid catalyzed rearrangement of pakistanamine () in 3N HCl leads to 1-0-methylpakistanine () together with small amounts of 1-0-methylkalashine () and (+)-armepavine (). Rearrangement of using methanol containing a little 3N HCl gives about equal amounts of and 1,10-di-O-methylpakistanine (). 相似文献
5.
A new synthesis of the pyranoquinolone alkaloids flindersine (), 8-methoxyflindersine (), N-methylflindersine (), zanthobunglanine () oricine () and veprisine () and the prenylquinolone alkaloids atanine (), preskimmianine () N-methylatanine (), O-methylglycosolone () and N-methylpreskimmianine () is described. 相似文献
6.
Methyl 4-0-benzoyl-6-bromo-6-deoxy-α-D-glucopyranoside (, Figure 1) was converted, via the corresponding ditosylate , into methyl 2,3-di-0-p-toluenesulfonyl-4-0-benzoyl-6-S-acetyl-6-thio-α-D-glucopyranoside () by a selective nucleophilic displacement of 6-bromo-group with thioacetate. Unexpectedly, on treating the compound with an excess of sodium methoxide in benzene-methanol (1:1) at room temperature, methyl 2-0-p-toluenesulfonyl-4,6-thioanhydro-α-D-gulopyranoside () was obtained in a yield of 84%. In order to determine the structure of the relatively unstable oily product , some stable crystalline derivatives (, and ) were prepared. Detailed analysis of the 1H-NMR-spectra (200 MHz) of and gave the conclusive evidence for the structure of A self-imposing mechanism of the clean and smooth transformation of to is proposed, involving: a) formation of (Figure 2) as a crucial intermediate and b) a highly regioselective epoxide opening in (at C-4) by an intramolecular nucleophilic attack of the mercaptide anion from C-6. 相似文献
7.
Tekant Gözler Belkis Gözler Amarendra Patra John E. Leet Alan J. Freyer Maurice Shamma 《Tetrahedron》1984,40(7):1145-1150
Konyanin (), obtained from (Rutaceae), is the first known 1,4-dihydroarylnaphthalene lignan in which the lactone carbonyl is bonded to C-3 rather than to C-2. Detailed NMR spectral data have been complied for the accompanying lignans (-)-kusunokinin () and diphyllin (). 相似文献
8.
《Tetrahedron》1986,42(16):4413-4420
(2,3,1')-Stegobinone [2,3-dihydro-2,3,5-trimethyl-6-(1'-methyl-2'-oxobutyl)-4H-pyran-4-one], the pheromone of L., was synthesized with stereocontrol at C-2 and C-1' starting from ethyl ()-3-hydroxybutanoate and methyl ()-3-hydroxy-2-methylpropanoate. The dihydro-γ-pyrone ring of the pheromone was constructed by an intramolecular acylation followed by acid-catalyzed cyclization. 相似文献
9.
A very convenient procedure for the conversion of (),O-5′-protected deoxyribonucleosides () into the triethylammonium salts of the corresponding 3′-(-chlorophenyl) phosphates () is described. Good yields of partially-protected 3′→5′-dinucleoside phosphates () are obtained from the latter () and 3′-unprotected nucleoside building blocks (). 相似文献
10.
Kenji Mori Hiroko Nomi Tatsuji Chuman Masahiro Kohno Kunio Kato Masao Noguchi 《Tetrahedron letters》1981,22(12):1127-1130
The absolute configuration at C-6 and C-7 of serricornin was established as (6, 7) by synthesizing its (6, 7- and (6, 7- isomers. 相似文献
11.
5-Azido-4-methoxycarbonyl-1-phenyl-1,2,3-triazole () and its phenyl substituted derivatives , rearrange at 60–80°C to give tetrazolyldiazoacetates , which have been isolated. When the reactions are allowed to go to completion, products derived from the diazo compounds are obtained; i.e. norcaradienes () from benzene solutions and imidazotetrazoles () from nitrite solutions. The latter decompose photochemically into diazacyclopentadienonimines (). A kinetic study of the rearrangement → has been carried out and the mechanism (Scheme VI) is discussed in comparison with the Dimroth rearrangement. 相似文献
12.
Merle A Battiste Donna.D McRitchie Paul G Gassman William F Reuss Jonathan N Chasman John Haywood-Farmer 《Tetrahedron letters》1979,20(23):2097-2100
Methyl substituent probes at the C-2 and C-2,C-4 positions of -tricyclo[3.2.1.02,4] octan-8-one() have provided kinetic evidence confirming the simultaneity of C-2,C-4 cyclopropane bond cleavage in the rate-determining step for thermal extrusion of carbon monoxide. 相似文献
13.
The acid catalysed reaction of 4-oxa-homoadamantan-5-one () with benzene yielded a mixture of 4a-phenyladamantan-2-one (), the equatorial isomer' () and 2-phenyl-2,4-o- benzenoadamantane () A plausible reaction pathway for the occurrence of . is put forward. The structure of , was deduced from spectroscopic data and reaction of the proposed intermediate 2,4a-diphenyladamantan-2-ol () with acid. 2,4-o-Ben-zenoadamantane () is prepared likewise. 相似文献
14.
On heating the furan endoperoxide () rearranges into the enol ester () and the bicyclic ozonide () affords instead the rearranged ozonide (). The process () → () represents an intramolecular Baeyer-Villiger rearrangement presumably via the dioxirane (D-2), while the process () → () represents intramolecular trapping of the carbonyl oxide (C-3). 相似文献
15.
The acid catalysed rearrangement of 8-methyl-pentacyclo(5.4.0.02,6.03,10.05,9)undecan-8-endo-o1 () to 3-methyl-(D3)-trishomocuban-4-o1 () provided the key step to the synthesis of the title compound (). 相似文献
16.
The stereoselective synthesis of 3-O-methyl-7α--toluenesulphonyl-8α, 9α, 14β-estradiol () and its 11-oxo derivative () thermolysis of 1β--butoxy-2α-[2-(4-methoxybenzocyclobutenyl)ethyl]-2β-methy1-3α-[2-(-toluenesulphonyl)ethenyl] cyclopentane () and its oxo derivative (), which were derived from condensation product () of optically active aldehyde () and 1-cyano-4-methoxybenzocyclobutene through and to selenides and , is described. 相似文献
17.
Novel carbon nucleophilic displacement reactions on Kamiya's azetidinone disulfide and the synthesis of the C-2 modified penams , and from the intermediates , , and are described. 相似文献
18.
Three quettamine type alkaloids, which incorporate either a benzofuran or a dihydrobenzofuran moiety within the molecular framework, have been obtained from . These are dihydrosecoquettamine (), secoquettamine (), and quettamine chloride (). Alkaloids and are racemates. Hofmann degradation of quettamine () provides secoquettamine () and the styrene which has a trans relationship between the hydrogens at C-1 and C-α, thus indicating the identical stereochemistry in quettamine. Emde reduction of quettamine leads to dihydrosecoquettamine () and the stilbene . Two other polar alkaloids in the plant are (+)-armepavine methochloride () and oblongine chloride (). An oblongine type alkaloid must be the biogenetic precursor for the quettamines. Arguments are presented favoring direct oxidative coupling in the biogenesis of the cularine alkaloids. 相似文献
19.
A new synthesis of oxindoles () isoquinolones () and benzazepinones () by the intramolecular amidoalkylation of aromatic amides of bismethoxycarbonylaminoacetic acid (, , ) is described. 相似文献
20.
The chiral bicyclic lactam () derived from levulinic acid and (S)-valinol is sequentially alkylated and then cleaved to 2,2-dialkyl levulinaldehyde () which is cyclized to the title products () in > 99% ee. 相似文献