共查询到20条相似文献,搜索用时 562 毫秒
1.
Masahiro Imoto Hiroyuki Yoshimura Nobuki Sakaguchi Shoichi Kusumoto Tetsuo Shiba 《Tetrahedron letters》1985,26(12):1545-1548
The first total synthesis of E. coli lipid A () is described. The synthetic compound was identical with a natural specimen and exhibited the full endotoxic activity. It was thus conclusively proved by this chemical synthesis that lipid A is the active principle of bacterial endotoxin. 相似文献
2.
M. Imoto S. Kusumoto T. Shiba E.Th. Rietschel C. Galanos O. Lüderitz 《Tetrahedron letters》1985,26(7):907-908
The chemical structure of E. coli lipid A was elucidated to be by determination of the nature of the individual acyl groups bound to the two hydroxyl groups in positions 3,3′ and the two amino groups of the D-glucosamine disaccharide phosphate backbone. 相似文献
3.
U. Zähringer B. Lindner U. Seydel E.Th. Rietschel H. Naoki F.M. Unger M. Imoto S. Kusumoto T. Shiba 《Tetrahedron letters》1985,26(51):6321-6324
The structure of the oligosaccharide portion of an Re lipopolysaccharide was determined as α-KDO-(2→4)-α-KDO-(2→6)-β-GlcN-α(1→6)-α-GlcN, bisphosphorylated at positions 1 and 4′. Taking into account the previous determination of the acylation pattern of the GlcN disaccharide, the total structure of Re LPS was thus established. 相似文献
4.
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
5.
Masaru Inage Haruyuki Chaki Shoichi Kusumoto Tetsuo Shiba 《Tetrahedron letters》1980,21(40):3889-3892
6-O-(2-Deoxy-2-myristoylamino-6-O-myristoyl-β-D-glucopyranosyl)-2-deoxy-2-myristoylamino-3,4-di-O-myristoyl-D-glucopyranose () was prepared in a synthetic approach to lipid A which is the active center of bacterial endotoxin. 相似文献
6.
Basil A. Burke Wilfred R. Chan Keith O. Pascoe John F. Blount Percy S. Manchand 《Tetrahedron letters》1979,20(36):3345-3348
A novel and highly functionalized crotofolane diterpene, crotofolin E (), has been isolated from Croton corylifolius L. (Euphorbiaceae) and its stereostructure determined from spectral and X-ray crystall crystallographic analyses. 相似文献
7.
A riboheptanucleotides G-C-A-A-C-C-A which has a sequence of the 3′-end of formylmethionine tRNA has been synthesized on a polyacrylmorpholide resin by the triester approach using dinucleotide blocks. 相似文献
8.
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
9.
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
10.
Contrary to the recent work of J. M. Thomas et al. (J. Chem. Soc. Chem. Commun., 678, 1981), it was found that a high-resolution neutron powder diffraction pattern of a sample of dehydrated Na zeolite A (with ratio 1.09) can be indexed and refined in the cubic groups (A. K. Cheetham and J. C. Taylor, J. Solid State Chem.21, 253, 1977) and , whereas in the rhombohedral space group refinement was unsuccessful. For two other samples having ratios of 1.03 and 1.12 the diffraction patterns again showed no evidence of rhombohedral distortion and can be indexed using a cubic unit cell. It appears that the Si, Al ordering of zeolite A, and hence the crystal symmetry, must depend upon the conditions of preparation of the zeolite. 相似文献
11.
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
12.
Two minor lipid components of the brown seaweed were characterized as (all Z) - 5′,7′-dihydroxy-2′-nonadeca-4,7,10,13,16-pentenyl-chrome chromone () and 5′,7′-dihydroxy-2′-pentadecylchrome (). 相似文献
13.
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
14.
Flow birefringence (FB) has been used to study sulphuric solutions of two homologous series of polyoxyphenylbenzoxazoleterephthalamides (POPhBT) differing in the position (para- or meta-) of phenyl ring in the chain. In the framework of the FB method alone by using the theory of flow birefringence for kinetically rigid wormlike chains, it was possible to determine quantitatively the optical anisotropy of the monomer unit Δa = (330 ± 30) 10?25 cm?3 and the length of the Kuhn segment and for para- and meta-isomers, respectively. Analysis of possible mechanisms of flexibility in the chains of both polymers gives theoretical values of the rigidity parameter A in good agreement with experimental values of A. confirming the validity of the molecular models used. 相似文献
15.
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
16.
Translational diffusion and intrinsic viscosity in 96% H2SO4 have been investigated for 20 samples of the para-isomer of polyoxyphenylbenzoxazoleterephthalamide (PpOPhBT) and 17 samples of its meta-isomer (PmOPhBT). The Mark-Kuhn equations have been obtained. The equilibrium rigidity of macromolecules in solution, calculated by using the wormlike chain theory, was characterized for PpOPhBT by the length of the Kuhn segment , the number of monomer units in a segment s = 17 and the coefficient of hindrance to intramolecular rotation in the chain σ = 1.5. For PmOPhBT the corresponding values are: , s = 5.9 and σ = 1.6. Analysis of flexibility mechanisms was carried out for PpOPhBT and PmOPhBT chains in solution. 相似文献
17.
A new hydrate of tungsten trioxide, has been obtained by hydrothermal treatment at 120°C of an aqueous suspension of either tungstic acid gel or crystallized dihydrate. This hydrate has been characterized by different methods. A crystallographic study was carried out from X-ray powder diffraction. The hydrate crystallizes in the orthorhombic system: a = 7.359(3) Å, b = 12.513(6) Å, c = 7.704(5) Å, Z = 12. The existence of structural relationships between the hydrate, , and the product of dehydration, hexagonal WO3, has permitted us to propose a structural model in agreement with the experimental data. must be regarded as an interesting compound because its dehydration leads to a new anhydrous tungsten trioxide, hexagonal WO3. 相似文献
18.
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
19.
The divinyl structure of protochlorophyllide (E443 F625) and of its chlorophyllide (E458 F674) photoreduction product was ascertained by nuclear magnetic resonance spectroscopy and by fast atom bombardment mass spectroscopy. These two phorbins are two newly discovered intermediates of the chlorophyll biosynthetic pathway in higher plants. Both tetrapyrroles exhibited recognizable ABX spin-spin splitting patterns which ar characteristic of divinyl tetrapyrroles. Fast atom bombardment mass spectroscopic data further confirmed the presence of two vinyl groups per molecule of protochlorophyllide (E443 F625) and of chlorophyllide (E458 F674). 相似文献
20.
The crystal structure of trisodium monophosphate hemihydrate was determined. The space group is and a unit cell contains eight formula units. The unit cell dimensions of are a = 9.631(3), b = 5.416(2), c = 16.938(8) Å, β = 102.60(5)°. The final R value is 0.027 for a set of 1430 independent reflections. This atomic arrangement is mainly a three-dimensional network of distorted NaO6 octahedra. The hydrogen bonding scheme is given. 相似文献