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1.
A facile one-step condensation of the cyclopentenyl α,-tosylate with the alkali metal salts of 6-chloropurine and uracil, afforded the protected carbocyclic nucleosides and , respectively, which were converted to neplanocin a () and cyclopentenyl uracil () by established methods. 相似文献
2.
In the presence of 1-methylimidazole, 2--acyl guanine (as in ), thymine (as in ) and uracil (as in ) residues react readily with the phosphorylating agent derived from 2-chlorophenyl phosphorodichloridate () and 1-hydroxybenzotriazole. 相似文献
3.
Direct ring-opening of the epoxide ring in 1-(5′--trityl-2′,3′-anhydro-β-D-lyxo-furanosyl) uracil (1) by lithium acetylide or vinylmagnesium bromide/cuprous iodide affords the corresponding 5′--trity]-3′--substituted-3′-deoxy--uridine species. 相似文献
4.
Simon S. Jones Colin B. Reese Samson Sibanda Aiko Ubasawa 《Tetrahedron letters》1981,22(47):4755-4758
The protection of uracil and 2--acyl guanine residues with 4--phenyl [or 4--(2,4-dimethylphenyl)] and 6--(2-nitrophenyl) groups as in [or ] and , respectively, is described. These -aryl protecting groups, which appear to withstand the usual conditions of oligonucleotide synthesis, may readily be removed by treatment with 2-nitrobenzaldoximate ions. 相似文献
5.
6.
A theory of the infrared spectra of hydrogen bonds in molecular crystals of Ch symmetry, containing, like uracil, four molecules and eight hydrogen bonds in the unit cell, is presented. The theoretical spectra are in good agreement in both the frequency and intensity distribution with experiment. The changes in the fine structure introduced by deuteration are quantitatively reproduced. 相似文献
7.
J Leitich 《Tetrahedron letters》1980,21(32):3025-3028
The relative rates of formation of and [2+2]cycloadducts of benzyne to , - and , -1,5-cyclooctadiene, - and -cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described. 相似文献
8.
In contrast with the reaction of α-aminonitriles a, the corresponding -acylated α-aminonitriles b-f and oxalyl chloride do not yield pyrazinone derivatives, but 5-aminooxazoles - or 4(5)-imidazolones , the latter being converted in some cases into imidazo [2,1-]isoquinoline-2,5,6(3)-triones. Reactions of compounds b-f and ethyl chlorooxoacetate provide evidence for a 5(4)-iminooxazole intermediate , which aromatizes to yield 5-aminooxazoles -; however, unaromatizable īntermediates of type - isolable as 5(4)y-oxazolones after hydrolysis - undergo a catalyzed Dimroth-type rearrangement to give imidazolone derivatives . 相似文献
9.
Two steroids, 3-oxo-chol-4-ene-24-oic acid () andi ts unsaturated analog have been isolated from the dorid nudibranch , and the acid has been shown to have antifeedant properties. 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.
Eiichi Kitazawa Akira Ogiso Shuji Takahashi Masaaki Kurabayashi Harumitsu Kuwano Tadashi Hata Chihiro Tamura 《Tetrahedron letters》1979,20(13):1117-1120
Two new diterpenelactones named plaunol A () and B () exhibiting anti-Shay ulcer activity were isolated from Thai medicinal plant, . Structure of was determined by X-ray analysis of its -bromobenzoate and structure of was deduced from the results of chemical correlation and the spectral data. 相似文献
12.
For 12-- locked retinal analogues, thermal equilibria are established between 11-, 13--1c and 13--2c and between 9-, 11-, 13--1d and 9-, 13--2d; a photoisomerization occurs to transform 2c to --2a and 2d to 9--2b 相似文献
13.
Hans Achenbach Andreas Mühlenfeld Benno Weber G.U. Brillinger 《Tetrahedron letters》1982,23(45):4659-4660
The new compounds – and have been isolated from cultures of 相似文献
14.
Alkylation of dibutylstannylene complexes of 3,4,6-tri--benzyl--mannopyranose, methyl 6--trityl-α--mannopyranoside and methyl α--mannopyranoside gives respectively β--mannopyranoside and 3--alkyl derivatives with high selectivity. 相似文献
15.
The 1H and 13C nmr spectra of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d6 or alkaline D2O, clearly show that it exists in a --conformation with carboxyl groups, thus being the first case of - preference of a bicyclo[3.3.1] nonan-9-one due to the presence of ,-2,4- substituents. 相似文献
16.
A new synthesis of (±), (+)- and (-)-lineatin (3,3,7-trimethyl-2, 9-dioxatricyclo [3.3.1.04,7] nonane, ) was achieved. The stereochemistry of (+)-lineatin was established as 1, 4, 5, 7 by an X-ray crystallographic analysis of an intermediate . 相似文献
17.
Giovanni Fronza Claudio Fuganti Piero Grasselli Giulio Marinoni 《Tetrahedron letters》1979,20(40):3883-3886
The enantiomeric alcohols () and (), obtained from (2,3) tartaric acid and, respectively, -threonine, have been used to construct the C6, enantiomeric deoxy amino sugar derivatives () and () 相似文献
18.
Naoko Morisaki Jun Furukawa Hisayoshi Kobayashi Shigeo Iwasaki Shigeo Nozoe Shigenobu Okuda 《Tetrahedron letters》1985,26(39):4755-4758
Deuterium labeled -6-protoilludene () was synthesized and fed to the illudin-producing fungus (ATCC 11719). The hydrocarbon () was incorporated into illudin-M () and -S (). 相似文献
19.
Hideo Kigoshi Yoshikazu Shizuri Haruki Niwa Hiyoyuki Yamada 《Tetrahedron letters》1982,23(14):1475-1476
Isolation and structural elucidation of two new acetylenic polyenes, -laurencenyne and -neolaurencenyne from the marine red alga were carried out, the former compound very recently being proposed to be a biosynthetic precursor of the C15 halogenated cyclic ethers, and . 相似文献
20.
Hideo Kigoshi Makoto Ojika Yoshikazu Shizuri Haruki Niwa Kiyoyuki Yamada 《Tetrahedron letters》1982,23(51):5413-5414
From a red alga (10, 11)-(+)-squalene-10, 11-epoxide was isolated and its asymmetric synthesis has been achieved starting from -farnesol. 相似文献