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41.
The stabilized phosphoranes, obtained from the three-component reaction between dialkyl acetylenedicarboxylates and urea or
N-methylurea in the presence of triphenylphosphine, undergo a smooth reaction in boiling toluene to produce iminophosphoranes
in good yields. Under the same reaction conditions, the phosphorane obtained from N-methylurea and dimethyl acetylenedicarboxylate yields methyl 1-methyl-2,6-dioxo-1,2,3,6-tetrahydro-pyrimidine-4-carboxylate. 相似文献
42.
M-Uracil复合物(M=Ca2+和Mg2+)特征振动的密度泛函理论分析 总被引:1,自引:0,他引:1
采用密度函数理论的B3LYP交换关联能泛函在6-311 G(2df,2p)基组水平上,对Ca2 、Mg2 与尿嘧啶(简称U)三种各互变异构体(简称U1、U2和U3)形成的复合物进行了优化计算,获得稳定复合物的构形,并对这些稳定复合物进行振动频率计算.分析计算结果发现由于离子的参与,单体分子振动的力常数和折合质量均会发生变化,导致红外振动谱线发生不同程度移动;进一步分析发现C-H和O-H键的氢原子作弯曲振动和伸缩振动的谱线移动不确定,直接与离子作用的氧原子参与的振动谱线会发生红移,不直接与离子作用的氧原子参与的振动谱线会发生蓝移. 相似文献
43.
Subodh Kumar Dharam Paul Harjit Singh 《Journal of inclusion phenomena and macrocyclic chemistry》2000,37(1-4):371-382
The reactions of uracil/benzimidazol-2(1H)-one with 1,3-bis(bromomethyl)benzene provide respectively1 3-bis[(3-bromomethylbenzene)methyl]uracil/benzimidazol-2(1H)-onewhich on subsequent cyclization with1,3-bis[(uracil-1-yl/benzimidazol-2(1H)-one-1-yl)methyl]benzenederivatives provide respectively calix[m]uracil[n]benzimidazoI-2(1H)-one[3]arenes[m =3, n = 0 (9); m = 2, n = 1 (10);m = 1, n = 2 (11) and m = 0, n = 3 (12)]. The heterocalixarenes 9–12, both in liquid–liquid and solid–liquid extraction experiments, selectively extract ammonium picrates over the similarly sized K+ picrate. The selectivity is much more pronounced in the case of solid-liquid extractions. Both in L-L and S-L extractions, 10 exhibits the highest order oft-BuNH3
+/K+ selectivity. 相似文献
44.
含嘧啶碱基和膦甲酸乙酯的聚磷酸酯的合成及其抗肿瘤活性 总被引:3,自引:0,他引:3
本文通过十一种二羟基嘧啶衍生物单体与P,P-二氯膦甲酸乙酯进行缩聚反应,合成了十一种新的含5-氟脲嘧啶、尿嘧啶、胸腺嘧啶和膦甲酸乙酯的聚磷酸酯。用核磁、红外光谱及元素分析确定了聚合物的结构。进行了部分聚合物抗动物肿瘤活性试验,含5-氟脲嘧啶和膦甲酸乙酯的聚磷酯对小鼠艾氏腹水癌的抑制率可达56%。 相似文献
45.
46.
47.
1-(3,4-二甲氧基)苯乙基-3-环氧丙基-5-氰基-6-甲基脲嘧啶的合成及晶体结构 总被引:1,自引:0,他引:1
标题化合物1-(3,4-二甲氧基)苯乙基-3-环氧丙基-5-氰基-6-甲基脲嘧啶是 由1-(3,4-二甲氧基)苯乙基-5-氰基-6-甲基脲嘧啶在NaOH水溶液中与环氧氯丙 烷反应制得。结构通过单晶X射线衍射分析确定,其晶体属于单斜晶系,空间群 P2_1/a, 晶胞参数:a = 1.09(10) nm, b = 1.43(10) nm, c = 1.20(8) nm, V = 1.868 nm~3,Z = 4, D_c = 1.32 Mg/m~3, F(000) = 784。并用波谱法对分离得 到的副产物进行了结构表征。 相似文献
48.
A. Zielenkiewicz G. Roux-Desgranges A. H. Roux J. P. E. Grolier K. L. Wierzchowski W. Zielenkiewicz 《Journal of solution chemistry》1993,22(10):907-918
Densities and specific heat capacities of aqueous solutions: 1,3,5,6-tetramethyluracil, 1,6-dimethyl-3-ethyluracil, 1,6-dimethyl-3-propyluracil, 1,6-dimethyl-3-butyluracil, 1,N4-trimethylcytosine, 1,N4-dimethyl-5-ethylcytosine, 1,N4 dimethyl-5-propylcytosine, 1,N4-dimethyl-5-butylcytosine were determined using flow calorimetry and flow densimetry at 25°C. Apparent molar volumes and heat capacities, van der Waals volumes and accessible surface areas were determined. It was stated that for alkylcytosines and alkyluracils partial molar volumes and heat capacities correlate linearly with the number of substituted methylene groups-CH2-as well as with the van der Waals volumes and accessible surface areas of the compounds studied; for cyclooligouracils the cyclization effect was discussed. 相似文献
49.
The PCILO method is used to calculate the stabilization energies of the anionic forms of uracil by water molecules forming the first hydration shell of the tautomers. The results show that the 1-HU– tautomer is more stabilized by the solvent effect than the 3-HU– tautomer by about 8 kcal/mole. The effect brings closer together the energies of the two tautomers which differ intrinsically by about 13 kcal/mole in favour of the 3-HU– form. It operates in the direction inferred from experimental studies.This work was supported in part by R.C.P. 173 of the Centre National de la Recherche Scientifique of France and in part by the Polish Academy of Sciences within the project 09.3.1. 相似文献
50.
Enthalpies of solution of thymine and uracil in water and in dimethylsulfoxide (DMSO) were measured calorimetrically in the temperature range 25–40°C. H
s
o
at 25°C for thymine and uracil in water were found to be 23.1±0.5 and 29.5±0.3 kJ-mol–1, respectively. In DMSO, H
s
o
were 7.9±0.1 and 10.2±0.1 kJ-mol–1, respectively. In aqueous solution C
p
o
for the two nucleic acid bases were relatively large and positive with C
p
o
of thymine being larger. Both transfer quantities H
t
o
and C
p,t
o
for the proceses H2ODMSO for the two nucleic acid bases were negative. It is proposed that, the differences in the values obtained for the two bases is due principally to increased order in the water adjacent to the methyl group in thymine. 相似文献