共查询到20条相似文献,搜索用时 15 毫秒
1.
Kay H. Boswell Leon F. Christensen Dennis A. Shuman Roland K. Robins 《Journal of heterocyclic chemistry》1975,12(1):1-9
A series of 6,8-disubstituted-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphates were prepared employing preformed 9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate precursors. Three synthetic approaches were utilized to accomplish the syntheses. The first approach involved a study of the order of nucleophilic substitution, 6 vs 8, of the intermediate 6,8-dichloro-9-β-D-ribofuranosyipurine 3′,5′-cyclic phosphates ( 2 ) with various nucleophilic agents to yield 8-amino-6-chloro-, 8-chloro-6-(diethylamino)-, 6-chloro-8-(diethylamino)-, 6,8-bis-(diethylamino)- and 8-(benzylthio)-6-chloro-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate (4, 9, 10, 11, 13) respectively and 6-chloro-9-β-D-ribofuranosylpurin-8-one 3′,5′-cyclic phosphate ( 5 ) and 8-amino-9-β-D-ribofuranosylpurine-6-thione 3′,5′-cyclic phosphate ( 6 ). The order of substitution was compared to similar substitutions on 6,8-dichloropurines and 6,8-dichloropurine nucleosides. The second scheme utilized nucleophilic substitution of 6-chloro-8-substituted-9-β-D-ribofuranosylpurine 3′,5′-cyclic, phosphates obtained from the corresponding 8-subslituted inosine 3′,5′-cyclic phosphates by phosphoryl chloride, 6,8-bis-(benzylthio)-, 6-(diethylamino)-8-(benzylthio),8-(p-chlorophenylthio(-6-(diethylamino)- and 6,8-bis-(methyl-thio)-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphates ( 14, 12, 20 , and 21 ) respectively, were prepared in this manner. The final scheme involved N1-alkylation of an 8-substituted adenosine 3′,5′-cyclic phosphate followed by a Dimroth rearrangement to give 6-(benzylamino)-8-(methylthio)- and 6-(benzylamino)-8-bromo-9-β-D-ribofuranosylpurine 3′,5′-cyclic phosphate ( 24 and 25 ). 相似文献
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Misbah Ul Hasan 《Magnetic resonance in chemistry : MRC》1980,14(4):309-311
meso-and dl-Diastereomers of a number of α,α′-disubstituted succinic acids have been shown to give different 13C NMR chemical shifts. The results can be satisfactorily explained on the basis of their conformational analyses. A discussion of the observed chemical shifts is presented, and the preferred conformation for each of several compounds is predicted on the basis of these chemical shifts. 相似文献
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Mahmoud Ahmed Amin Helen Stoeckli-Evans Albert Gossauer 《Helvetica chimica acta》1995,78(7):1879-1886
In 10 steps, 3′,4′-diethynyl-2′,3′,5′-trideoxy-5′-noruridine ( 14 ) was synthesized in 5% overall yield from commercial uridine, using conventional methods of nucleoside chemistry. As two functional groups capable to react with each other are present in the same molecule, the synthetic compound is able to form polymers, similar to the polynucleotides, by an acetylene coupling reaction. 相似文献
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The analysis of the 13C FT NMR spectra of 2-hetera[3](1,1′)ferrocenophanes containing an oxygen, sulphur, selenium atom, phenyl-substituted nitrogen or a methylene group in the 2-position of the bridge has been carried out. The electronegativity of this fragment affects both chemical shifts and coupling constants, but no simple relationship was found. 相似文献
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Victor J. Bauer Helen H. Ong Raymond W. Kosley 《Journal of heterocyclic chemistry》1982,19(5):1069-1072
The 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro[isobenzofuran-1,4′-thiopyran] ring system ( 2a ) has been prepared from o-bromobenzoic acid. The 1,2′,3,3′,5′,6′-hexahydro-3-phenylspiro[isobenzofuran-1,4′-pyran] ring system ( 3a ) has been prepared from 2-bromobenzhydrol methyl ether. Several 3-(dimethylaminoalkyl) derivatives of both 2a and 3a were prepared by lithiation followed by alkylation. 相似文献
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The synthesis of the polyhalogenated phenylalanines Phe(3′,4′,5′-Br3) ( 3 ), Phe(3′,5′-Br2-4′-Cl) ( 4 ) and DL -Phe (2′,3′,4′,5′,6′-Br5) ( 9 ) is described. The trihalogenated phenylalanines 3 and 4 are obtained stereospecifically from Phe(4′-NH2) by electrophilic bromination followed by Sandmeyer reaction. The most hydrophobic amino acid 9 is synthesized from pentabromobenzyl bromide and a glycine analogue by phase-transfer catalysis. With the amino acids 4, 9 , Phe(4′-I) and D -Phe, analogues of [1-sarcosin]angiotensin II ([Sar1]AT) are produced for structure-activity studies and tritium incorporation. The diastereomeric pentabromo peptides L - and D - 13 are separated by HPLC. and identified by catalytic dehalogenation and comparison to [Sar1]AT ( 10 ) and [Sar1, D -Phe8]AT ( 14 ). 相似文献
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Cong Zhang Christian Ludin Marcel K. Eberle Helen Stoeckli-Evans Reinhart Keese 《Helvetica chimica acta》1998,81(1):174-181
(S)-5,5,5,5′,5′,5′-Hexafluoroleucine ((S)- 13 ) of 81 % ee is prepared from hexafluoroacetone ( l ) and ethyl bromopyruvate (= ethyl 2-oxopropanoate) in 7 steps with an overall yield of 18% (Schemes 1 and 2). Key step in this sequence is the highly enantioselective reduction of the carbonyl group in α-keto ester 4 either by bakers' yeast (91 % ee) or by ‘catecholborane’ 6 utilizing an oxazaborolidine catalyst, yielding hydroxy ester (R)- 5 with 99% ee. The absolute configuration was determined by X-ray analysis of the HCl adduct (S,R)- 9b of (2S)-N-[(R)- l-phenylethyl]-5,5,5,5′,5′,5′-hexafluoroleucine ethyl ester. 相似文献
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The preparation of 1′-and 3′-amino-5′,6′,7′,8′-tetrahydro-2′-acetonaphthones (IIIa and IIIb) is described, by reduction of the low temperature nitration products of 5′,6′,7′,8′-tetrahydro-2′-acetonaphtone (I). The structures of the nitro isomers (IIa and IIb), and the reduction products, IIIa and IIIb, were elucidated spectroscopically. By known reactions, a series of new heterocyclic compounds prepared from the o-aminoketones, IIIa and IIIb, resulted in two series of new heterocyclic compounds. 相似文献
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J. W. Mcfarland B. M. Howe J. D. Lehmkuhler D. C. Myers 《Journal of heterocyclic chemistry》1995,32(6):1747-1750
Formylation of 2,2′,5′,2′-terfuran ( 1 ) with N-methylformanilide and phosphorus oxychloride gave 5-formyl-2,2′,5′,2′-terfuran ( 2 ) and 5,5′-diformyl-2,2′5′,2′-terfuran ( 3 ). Reduction of 2 and 3 afforded 5-hydroxymethyl-2,2′,5′,2′-terfuran ( 4 ) and 5,5′ dihydroxymethyl-2,2′,5′,2′-terfuran ( 5 ), respectively. Terfuran 1 reacted with phenylmagnesium bromide to give 5-(phenylhydroxymethyl)-2,2′,5′,2′-terfuran ( 6 ), and was carbonated to 5-carboxy 2,2′,5′,2′-terfuran ( 7 ) and 5,5′-dicarboxy-2,2′,5′,2′-terfuran ( 8 ). Bromination of 1 with N-bromosuccinimide gave 5,5′-dibromo 2,2′,5′,2′-terfuran ( 9 ). 相似文献
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Eduardo Diaz Hctor Barrios Francisco Yuste Jos Luis Aguilera William F. Reynolds Marie Rose Van Calsteren Christopher Jankowski 《Journal of heterocyclic chemistry》1993,30(1):97-104
The reaction of dibenzalcyclohexanone with hydroxylamine hydrochloride afforded three compounds 1–3 including the aziridine 3 showing a 3′,3a′-trans configuration. Now we report on the isolation of a new aziridine 4 , possessing a 3′,3a′-cis configuration. Its structure was deduced by 2D nmr and single crystal X-ray diffraction studies. 相似文献
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Raman spectra of Fe3+ and Pd2+ octaethylporphyrin (OEP) and their α′, β′, γ′, and δ′ deutero derivatives were measured with the 5145, 4880 and 4765 Å lines of an Ar ion laser. Raman bands due to methine-bridge stretching vibrations were assigned and their vibrational amplitudes were calculated from the observed frequency shifts on deuterium substitution of methine-bridge hydrogens. These vibrations correspond to the spin-state sensitive Raman bands of heme proteins. On the basis of symmetry considerations and the observed polarizations, vibrational assignments of other Raman bands were made. 相似文献
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Yeonjoong Yong Seunghyun Ahn Doseok Hwang Hyuk Yoon Geunhyeong Jo Young Hwa Kim Sang Ho Kim Dongsoo Koh Yoongho Lim 《Magnetic resonance in chemistry : MRC》2013,51(6):364-370
Chalcones are of interest to medicinal chemists because their structures can be easily modified with various functional groups. The syntheses and biological activities of chalcones from natural sources are well known. In this study, 24 2′‐hydroxychalcones bearing methoxy substituents were synthesized, among which five are new. The NMR data for all synthesized chalcones are described for the first time. The complete assignments of the 1H and 13C NMR data can be used for the identification of newly discovered and widely isolated, synthesized chalcones. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Aiping Yang Stephen Hughes Masami Kuroda Yotaro Shiraishi Takayoshi Kobayashi 《Chemical physics letters》1997,280(5-6)
By analyzing the stationary absorption spectrum of 2,2′:5′,2″-terthiophene in dichloromethane at room temperature, the zero–zero S1←S0 transition energy is determined. Time-resolved fluorescence measurements show that the S1→S0 radiative relaxation in various solvents decays exponentially with a common time constant of 170±10 ps. The fluorescence anisotropy of 2,2′:5′,2″-terthiophene in dichloromethane is also studied and the transient dichroism is interpreted in terms of the revolution of a hydrodynamic prolate ellipsoid with the emission dipole aligned parallel to the long molecular axis. 相似文献