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1.
trans- -Isopropenyl-4-methylene-spiro[2.x]alkanes ( and ) react at 0°C with CSI to give as major products the trans bicyclic cycloazanondienones (-) and as the minor products bicyclodihydro-azepinones ( and ), and the respective cis isomer of bicyclic cycloazanondienones ( and ). 相似文献
2.
Irradiation of thioxanthenethione with the alkyl- and alkoxysubstituted butatrienes a-d gives the thietanes a-d the cyclobutanethione is formed as a byproduct. Free radical addition of iC3H7SH to a predominantly occurs via terminal attack of the thiyl radical on the π-system. 相似文献
3.
A synthesis of (2S,3S,7S)-3,7-dimethylpentadecan-2-yl acetate () and propionate () is described. (2S)-2-Methyldecan-1-yl lithium () was reacted with (3S,4S)-3,4-dimethyl-γ-butyrolactone () to yield the ketoalcohol which upon Huang-Minlon reduction furnished (2S,3S,7S)-3,7-dimethylpentadecan-2-ol (). Acylations gave the esters and . The (2S)-2-methyldecan-1-yl lithium was obtained via asymmetric synthesis. The chiral lactone was obtained from (2S,3S)-trans-2,3-epoxybutane and dimethyl malonate. 相似文献
4.
4-O-(2,6-diamino-2,3,4,6-tetradeoxy-3-C-methyl-β-L-arabino and lyxo-hexopyranosyl) and 4-O-(2-amino2,3,4,6-tetradeoxy-5-c-methyl-L-threo-hexopyranosyl-6-O-(3-amino-3-decxy-α-D-glucopyranosyl)-2-deoxystreptamine (, and ) were synthesized from a kanamycin B derivative () by regiospecific methylation and stereospecific hydrogenation followed by removal of masking groups, converting a D-sugar moiety (4-O-glycoside portion) into L-sugar. The usual conformation of and were determined as boat and skew by 250 MHz PMR spectra respectively. 相似文献
5.
Methyl 5(S), 6(S)-oxido-11-oxo-7-cis-9-trans-undecadienoate was prepared and used for the synthesis of the novel 7-cis-LTD4 () as well as, after isomerization to the all-trans dienal ester , for that of the natural leukotrienes. 相似文献
6.
The N-hydroxyazetidines and are prepared startinfrom 2,3-dihydroazete 1-oxides ( and 0 by reduction with sodium borohydride and by reaction with a nucleophile, respectively. The N-thydroxyazetidines and can be oxidized with mercury (II) oxide to the corresponding nitrones ; oxidation of the N-hydroxyazetidine (unsubstituted at C-4) with equivalent of lead tetraacetate tyields the N-tacetoxy β-lactam . 相似文献
7.
Jean-Raymond Gavarri Claude Carel Dominique Weigel 《Journal of solid state chemistry》1979,29(1):81-95
The structure of wüstite Fe1?zO is studied by neutron diffraction on one polycrystalline sample under equilibrium conditions at high temperature. The mean isotrope temperature factor B is expressed as a sum of two parts, BTh and BSt, which vary linearly with a single parameter, respectively temperature and z. A classification is established for clusters () settled from m vacancies in octahedral sites and n FeIII ions in interstitial sites. Sixteen values have been experimentally determined for the vacancies to interstitials ratio . A constant value of ?, which is lower than 3, is observed. This result characterizes the short-range order. It eliminates several possibilities of clusters like those obeying the relation . Other clusters, namely () or (), might agree. The () and () clusters obtained from () clusters joined by an edge would be the more likely. An analysis of diffuse scattering eliminates the hypothesis of large domains with inverse spinel structure. The structural differences between the three varieties W1, W2 and W3 would not be found in a structural change of clusters. 相似文献
8.
Tatsuhiko Kanmera Sannamu Lee Haruhiko Aoyagi Nobuo Izumiya 《Tetrahedron letters》1979,20(46):4483-4486
A series of cyclo (Δaminoacyl-L-Ala) () (Δ=α,β-dehydro) were prepared from cyclo(Gly-L-Ala) and corresponding aldehyde, and hydrogenated with Pd black in MeOH. Chiral inductions producing cyclo (L-aminoacyl-L-Ala) () from were 96–99% in the case of L-Aba (2-aminobutanoic acid), L-Val, L-Leu, and L-App (2-amino-5-phenylpentanoic acid) as an L-aminoacyl moiety in . Pure L-Leu, L-Aba, and L-App were synthesized in preparative scale from corresponding through asymmetric hydrogenation and acid-hydrolysis. 相似文献
9.
Motomasa Kobayashi Tohru Yasuzawa Minoru Yoshihara Hideo Akutsu Yoshimasa Kyogoku Isao Kitagawa 《Tetrahedron letters》1982,23(50):5331-5334
The structures of four new prostanoids named claviridenone-a, -b, -c, and -d, which were isolated from the Okinawan soft coral Clavularia viridis, were elucidated as , , , and , respectively. 相似文献
10.
A tritriacontanucleotide which has the sequence of the 5half molecule of E.coli glycine tRNA2, was synthesized by the phosphotriester method involving p-anisidate protection for the 3phosphate ends. Di- and trinucleotide units were prepared from 5dimethoxytrityl-2O-tetrahydrofuranyl-3?-O-(o-chlorophenyl)phosphoryl derivatives of uridine, N-benzoylcytidine, N-benzolyadenosine and N-iso-butyrylguanosine by condensation with 35unprotected nucleosides followed by phosphorylation to give 3phosphodiester blocks. The 3terminal dimers and trimers were synthesized by using 3(o- chlorophenyl)phosphoro-p-anisidates instead of 3?,5?-unprotected nucleosides. The 3?-phosphodiesters of oligonucleotides with a chain length of larger than 5 were obtained by removal of the 3?-phosphoro-p-anisidate with isoamyl nitrite. The 5dimethoxytrityl group was removed by treatment with zinc bromide under anhydrous conditions. Fragments were designed to use common dimer blocks and to reduce the step for 5deblocking of larger fragments. Finally a 3phosphodiester block with a chain length of 20 was condensed with a 5OH component (tridecanucleotide). The fully protected 33 mer was deblocked and purified by chromatography. The structural integrity of the product was confirmed by mobility shift analysis and complete digestion with RNase T2. 相似文献
11.
Neolupenyl acetate (), tarolupenyl acetate () and their corresponding alcohols ( and ) were isolated from the roots of Taraxacum japonicum, and their structures were established as the members of migrated lupane series. 相似文献
12.
tert-Butyl azidoformate () reacts with the conjugate bases of , , (R1 = R2 = CH3), and (R1 = CH3, R2 = H) to give products [, , , and , respectively] in addition to the expected N-(tert-butoxycarbonyl)indole derivatives. 相似文献
13.
Asymmetric cyclizations of methyl (E)-3-oxo-9-phenoxy-7-nonenoate () or methyl (E)-3-oxo-9-(methoxycarbonyl)oxy-7-nonenoate () without added base were carried out in the presence of a catalytic amount of palladium(II) acetate and chiral diphosphine as ligands. Allylic carbonate reacted by use of Pd(OAC)2-(S)-(R)-BPPFA at room temperature to give (R)-3-vinylcyclohexanone (), after decarboxylation, in up to 48% e. e. 相似文献
14.
Three new high molecular weight bromotyrosine-related metabolites, , and , were isolated from the sponge Aplysina ( Verongia) fistularis forma fulva, and their structures were determined from high resolution 1H NMR and other spectroscopic data. The new metabolites are formally derived by combination of major segments of two known Aplysina metabolites and . 相似文献
15.
Marek Chmielewski Piotr Guzik Bogumiła Hinjtze Włodzimierz M. Daniewski 《Tetrahedron》1985,41(24):5929-5932
Butyl 2-0-acetyl-4,5-anhydro-3,6-dideoxy-DL-xylo-hexaldonate () in the presence of SnCl4 underwent an intramolecular rearrangement to give 2,5-anhydro ester . On the other hand the lyxo epimeric epoxide under the same conditions afforded esters and . Ester was transformed into racemic epiallomuscarine (), whereas the isomer into racemic epimuscarine (). 相似文献
16.
Irradiation of xanthenethione with bis(tert-butylthio)ethyne yielded both the expected α,β-unsaturated dithioester and surprisingly its proposed intermediate thiete as crystalline compounds. In solution an equilibrium between both compounds has been observed. 相似文献
17.
Two new triterpenoid acids, designated as plectranthoic acid A and plectranthoic acid B, have been isolated from P. rugosus and are characterised as (20-S)-3α-hydroxy-18α,19α--urs-12-en-30β-oic acid and (14-S)-3α-hydroxy-18α, 19α -urs-12-en-27α-oic acid. 相似文献
18.
Tert-butylisocyanide inserts into the carbon-sulfur bond of α-cyano sulfides - to give thioimidates -. The thioimidates can also be obtained via the chlorine substitution of the tert-butylimino chloro sulfides -, which is a more general method. These thioimidates rearrange to E and Z isomers of N-vinylcarbamates - via a 1,3 C to N migration of the alkoxycarbonyl group. 相似文献
19.
Ronald D. Brown Peter D. Godfrey Donald C. McGilvery Jonathan G. Crofts 《Chemical physics letters》1981,84(3):437-439
Microwave—optical double resonance signals have been detected in a mass-selected ion-beam spectrometer for 12C16O+. With the optical excitation of fluorescence from the R1 () line of the (0,0) band of the A2Π ← X2∑ transition of 20350.6 cm?1, the microwave resonances occurred at 118101.8 ± 0.2 MHz and at 117694 ± 2 MHz corresponding to the N= 1, J = ← N = 0, J = and the N = 1, J = ← N = 0, J = transitions. 相似文献
20.
《Tetrahedron》1987,43(13):3021-3030
A new synthesis of 9,10-dimethoxy-1,3,4,6,7,11b-hexahydro-2H-benzo aquinolizin-2-one ( and its 3-ethyl derivative via the corresponding 2-(3,4-dimethoxyphenyl)-4-piperidone ethylene acetals is reported. Alkylation of 2-arylpipendires with 2-bromoethanol followed by oxidation of the resulting amino alcohols with oxalyl chloride and dimethyl sulfoxide afforded the aldehydes , which were cyclized with hydrochloric acid to give 7-hydroxybenzo[α]quinolizidines . The reduction of with trinethylsilane and subsequent acid hydrolysis led to benzo aquinolizidin-2-ones . 相似文献