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1.
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
2.
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
3.
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
4.
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
5.
Martine Bonin José R Romero David S Grierson Henri-Philippe Husson 《Tetrahedron letters》1982,23(33):3369-3372
The cis 2,6-dialkylpiperidine alkaloid (±) dihydro-pinidine and the trans alkaloid (±) solenopsin A were synthesized from a common α-aminonitrile synthon . The key step in this synthesis was the stereoselective reductive decyanation of the 1-benzyl-2cyano-2′, 6-dialkylpiperidines and . 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.
8.
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
9.
Dehydrotripeptides, X-CH(Ri)-ΔPhe-CH(Rk)COOMe (: X = tBOC-NH,CBZ-NH, CF3CONH and N3), were employed for the asymmetric hydrogenation catalyzed by chiral rhodium complexes and it was found that tBOC- brought about by far the best results. Stereoselective dideuteration of a tBOC- was successfully performed. 相似文献
10.
Total synthesis of the Cannabis alkaloid cannabisativine () was stereoselectively achieved for the first time in a racemic form starting from a dihydropyridine derivative () by way of , , and . 相似文献
11.
The cycloaddition of α,β-epoxyaldehydes or ketones () with the ketene acetal MeHC=C(OMe)2 () gives epoxyoxetanes () in high yields. Without isolation they can be transformed into 4-hydroxy-5-(1-hydroxyalkyl)-γ-butyrolactones () via the epoxy esters and trihydroxy esters (). The lactones appear to be valuable precursors for the synthesis of 5-(1-hydroxyalkyl)-3-methyl-2-5H-furanones () and 3-methyl-5-ylidene-2-5H-furanones () 相似文献
12.
Takashi Ishizu Kazunobu Harano Masami Yasuda Ken Kanematsu 《Tetrahedron letters》1981,22(17):1601-1604
The cyclocoupling reaction of 2-oxyallyl-Fe(II) cation () with cycloheptatrieneiron tricarbonyl () gave the σ,π-allyliron tricarbonyl complex (). Structure of the complex () was fully established by X-ray analysis. Oxidative degradation of the complex () with o-chloranil afforded a single iron free compound () which was indicated that a carbonyl insertion took place during oxidation. 相似文献
13.
14.
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
15.
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
16.
1-Methyl-2-(1′-cyano-1′-trimethylsilyloxy)alkyl-1H-imidazoles () were easily prepared from the corresponding stable carbonyl compounds, 1-methyl-2-acyl- 1H-imidazoles (). When the quarternary salts of were treated with various nucleophiles, reactive acyl species, which was presumed to be acylcyanide (), was generated in situ under CC bond fission to result in producing the corresponding acylated compounds (–) in good yields. 相似文献
17.
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
18.
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
19.
Irradiation of 2,4,6-tri-(tert,-butyl)thiobenzaldehyde with some alkoxy-, alkylthio-, and phenyl-allenes - gave one stereoisomer of a (2+2)-cycloadduct, viz. thietane in high yields (75–95%). Ringclosure is in agreement with MNDO-calculations. 相似文献
20.
Under both static and flow thermolysis conditions, several compounds with an “aspidosperma” framework rearranged to “vinca” derivatives. Thus (-)1,2-dehydroaspidospermidine () rearranged to (-) gave vincane . Compound rearranged to vincamine () and 16-epi vincamine () under either condition ; increasing the temperature resulted in formation of apovincamine () (pyrolysis) or vincamone thermolysis). 相似文献