SYNTHESIS OF 6-AMINO, 6-METHOXY AND 6-ETHOXY PURINENUCLEOSIDE DERIVATIVES

A convenient route for the conversion of inosine to the corresponding 6-amino, 6-methoxy and 6-ethoxy derivatives is reported. This conversion can be achieved by ammoniation or etherification of the 6-pyridinium intermediate(3) which can be readily produced under mild reaction conditions. The chemistry and characterization of these compounds are presented, A plausible mechanism of the reaction is proposed.     

Isomerization of B6, B6 − and B6 + clusters

The interconversions between isomers with the same spin multiplicity of neutral B₆ and charged B₆ ^? and B₆ ⁺ clusters have been investigated at the B3LYP/6-311+G* level of theory, including determination of the minimum energy pathways with transition states connecting the corresponding reactants and products. In dynamic calculations, 26 isomers were optimized, including 11 novel isomers. In order to further refine the energies, single-point B3LYP/6-311+G(3df) calculations were carried out on the corresponding B3LYP/6-311+G* geometries of all isomers of B₆, B₆ ^? and B₆ ⁺ and the corresponding isomerization transition states. The stability of each isomer of B₆ (singlet and triplet states), B₆ ^? (doublet state) and B₆ ⁺ (doublet state) was analyzed from both thermodynamic and dynamic viewpoints.     

C60NH5/6, 6/6异构体的理论研究

用半经验的AM1, PM3及ab initio方法对C60NH两种异构体的结构及光谱进行了理论计算。结果表明, 具有开环结构的C60NH的5/6异构体稳定性要高于具有闭环结构的6/6异构体。计算了两种异构体开环与闭环过程的反应坐标, 发现6/6开环异构体是势能面上的一局部最小点, 而5/6闭环异构体不存在6/6异构体的H可以在两种镜面异构体之间快速翻转, 使其核磁共振谱呈现C2v对称性。通过振动分析确认了所优化的构型确实为势能面的能量最低点, 并得到了C60NH各异构体的红外光谱。     

C6H6Cl6正电性集团对其物理性质的影响

本文对C_6H_6Cl_6不同的三氢正电集团、独立双氢正电集团与溶媒的耦合适应性进行了研究,讨论了这些正电性集团对溶媒化程度的影响,并预测了一些物质的相对溶解度,阐述了C_6H_6Cl_6异构体间熔点差异的原因.     

Octahedral rhodium cluster [Rh6Cp6(μ6-C)]2+(PF6 -)2

The 86-electron dicationic octahedral rhodium cluster [Rh₆Cp₆(_μ6-C)]²⁺(PF₆ ^-)₂ containing Cp ligands and the interstitial carbon atom was synthesized by the reaction of Rh₃Cp₃(μ-CO)₃ with RhCp(C₂H₄)₂ Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 395–396, February, 1999     

Synthesis of oligo-6-bromo-6-deoxy-β-cyclodextrins

Two methods of synthesis of oligo-6-bromo-6-deoxy--cyclodextrins, with use of the Vilsmeier-Haack reagent and via tosyl derivatives of -cyclodextrin, were compared. The second method holds more promise, since it allows a desired number of bromine atoms to be introduced into the -cyclodextrin molecule instead of hydroxy groups. A correlation between the decomposition onset points of oligo-6-bromo-6-deoxy--cyclodextrins and the number of bromine substituents in them was revealed.Translated from Zhurnal Obshchei Khimii, Vol. 74, No. 10, 2004, pp. 1743–1745.Original Russian Text Copyright © 2004 by Kurochkina, Trushkin, Grachev, Nifantev.This revised version was published online in April 2005 with a corrected cover date.     

MoF6 and WF6: Nonrigid Molecules?

Calculations reveal that the octahedral-trigonal prismatic-octahedral rearrangement has particularly low-energy barriers for MoF6, WF6, and (hypothetical) CrF6. Experimental evidence is obtained from the dynamic 19F NMR spectra of the derivatives CF3-CH2-O-MoF5, CF3-CH2-O-WF5, C6F5-O-MoF5, C6F5-O-WF5, and (CF3)3C-O-WF5. The ground-state structure of all these compounds is octahedral; at elevated temperatures the nonequivalent metal-bound fluorine atoms undergo an intramolecular exchange. The exchange mechanism could be a 3+3 or a 2+4 twist; calculations favor the 3+3 twist.     

Continuous photochemical generation of catalytically active [CpRu]+ complexes from CpRu(η6-C6H6)PF6

Inter- and intramolecular ene-yne coupling reactions catalyzed by a species generated in situ via photolysis of CpRu(η(6)-C(6)H(6))PF(6)--an inexpensive, readily available, and shelf-stable complex--have been demonstrated under conditions of continuous flow. Importantly, the catalyst can be recovered quantitatively at the end of the reaction. Various functional groups are tolerated by the reaction, which affords skipped diene products in high yields.     

The Benzoylation of 6-Methyluracil and 5-Nitro-6-methyluracil

6-Methyluracil and 5-nitro-6-methyluracil react with variable molar quantities of benzoyl chloride in acetonitrile-pyridine at room temperature to give I-N, 3-N-dibenzoyl-6-methyluracil 3b and l-N-benzoyl-5-nitro-6-methyluracil 4b. The reactive rates of debenzoylation of 3b and 4b were investigated.     

The estimation of ν6 of octahedral XY6 species

The inactive F_2u vibration frequency of octahedral XY₆ type species for which this frequency is known, was estimated from the remaining frequencies using the Urey—Bradley (UBFF) and orbital valency (OVFF) force fields and their modifications. Various modifications of the generalized valency force field (GVFF) were also considered. Estimated values were scattered within a wide range and the average discrepancy varied from 20 (UBFF) to 68% (modified OVFF). The condition ν₆ = ν₅/√2 (Wilson's rule), with an average discrepancy of 15% gave the closest estimate of the assigned values.     

A Novel Method for Synthesizing 6-Chloro and 6-Methoxypurinenucleoside

Starting from tetraacetylribofuranose (Ⅰ) and 6-chloropurine (Ⅲ), in the presence ofp-toluenesulfonic acid as catalyst, the intermediate 2',3',5'-tri-O-acetyl-6-chloropurine nucleoside (Ⅲ) was synthesized for the first time under microwave irradiation in the yield of 80.1%. The title compounds 6-chloro-9-β-D-purinenucleoside (Ⅳ) and 6-methoxy9-β-D-purinenucleoside (Ⅴ) were easily obtained by treatment the intermediate (Ⅲ) with NH3/CH3OH and Na2CO3/CH3OH in the yields of 78.8% and 76.9%, respectively. Structures of Ⅳ and Ⅴ have been identified by 1H NMRand elementary analysis. The optimal conditions for condensation were as follows: n(Ⅰ): n(Ⅱ)= 1: 1, m(TsOH):m(6-chloropurine)=3 × 10-2, microwave irradiation at 595 W for 4.5 min, at 462 W for 1 min, at 119 W for 0.5 min;aminolysis condition for Ⅳ: room temperature for 5 min; alkaline hydrolysis conditions for Ⅴ: reflux for 5 h.     

Electron Transfer Reaction between M-C_6H_6 and M~ -C_6H_6 Complexes in the Gas Phase: Density Functional Theory Study

Significant progress has been made in understanding the nature of the transition state andthe paths for electron transfer, especially the influences of environmental factors and themolecular properties on the electron transfer rate. These classical and semi-classical, aswell as quantum-mechanical theory, have been very successful in rationalizing severalstructure-reactivity relationships and in predicting novel features of reactivity. Thesemodels established some links between the electron tra…     

SF6-UF6体系中六氟化铀的振动弛豫研究

本文以脉冲CO_2激光激发SF_6, 经碰撞再使UF_6分子激发, 通过测定振动受激UF_6的紫外吸收变化, 研究了六氟化铀分子的振动弛豫过程。对于2.0. Torr SF_6+2.0 Torr UF_6体系, 在220-320 nm范围内测定了UF_6的紫外吸收信号随时间的变化, 测得UF_6三类不同振动受激态分子间的V-V能量弛豫时间分别为6.8, 9.0和26 μs, 相应的V-T能量弛豫时间为42, 8和1 ms。此外, 还讨论了SF_6-UF_6体系中振动能量弛豫的机理。     

△~6-6-甲基甾体的合成

本文报告△~6-6-甲基化合物S,△~6-6-甲基可的唑、△~6-6-甲基可的伀及△~6-6-甲基-17α-乙酰氧基黄体酮的合成。     

STRUCTURE OF 6-EPICHASMANINE

ＳＴＲＵＣＴＵＲＥＯＦ６－ＥＰＩＣＨＡＳＭＡＮＩＮＥ￥ＺｈｅｎｇＢａｎｇＬＩａｎｄＦｅｎｇＰｅｎｇＷＡＮＧ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙｏｆＭｅｄｉｃｉｎａｌＮａｔｕｒａｌＰｒｏｄｕｃｔｓ．ＳｃｈｏｏｌｏｆＰｈａｒｍａｃｙ，ＷｅｓｔＣｈ...     

铽锰基化合物TbMn6Sn6的结构和磁性

研究了重稀土金属化合物ＴｂＭｎ６Ｓｎ６的晶体结构、内禀磁性及其矫顽力随和外场变化的规律。ＴｂＭｎ６Ｓｎ６为ＨｆＦｅ６Ｇｅ６型六角型结构，晶格常数为：ａ＝０．５５６１ｎｍ，ｃ＝０．９０４７７ｎｍ，单胞体积为０．２４１ｎｍ＾３，居里温度ＴＣ＝４２１Ｋ。ＴＭｎ６Ｓｎ６化合物在外场较弱时，热磁曲线呈亚铁磁性；当外场较强时，则表现出铁磁行为，具有变磁性，ＴｂＭｎ６Ｓｎ６的矫顽力随温度变化，当温度Ｔ＝２００Ｋ     

SF_6-UF_6体系中六氟化铀的振动弛豫研究

本文以脉冲CO_2激光激发SF_6,经碰撞再使UF_6分子激发,通过测定振动受激UF_6的紫外吸收变化,研究了六氟化铀分子的振动弛豫过程。对于2.0.Torr SF_6+2.0Torr UF_6体系,在220-320 nm范围内测定了UF_6的紫外吸收信号随时间的变化,测得UF_6三类不同振动受激态分子间的V-V能量弛豫时间分别为6.8,9.0和26μs,相应的V-T能量弛豫时间为42,8和1ms。此外,还讨论了SF_6-UF_6体系中振动能量弛豫的机理。     

Zn掺杂对量子点Cd_6Se_6及其配合物Cd_6Se_6-(OPMe_3)_6结构和性质影响的密度泛函理论研究

采用密度泛函理论对有机配体三甲基氧膦OPMe_3吸附到掺杂量子点ZnmCdnSe_6(m+n=6)上形成吸附产物的结构和性质进行了研究。金属原子Zn和Cd与配体OPMe3中的O原子形成Zn-O和Cd-O配位键,其吸附能、电荷分布、HOMO、LUMO和电子吸收光谱等性质随着掺杂Zn原子的增多而逐渐变化。研究表明向Cd6Se6中掺杂Zn原子使其电子吸收光谱出现蓝移,随着掺杂原子的增多,蓝移现象就越明显,研究结果有助于纳米材料的设计和合成。     

P6（D6h）和P12（D6h的从头算研究

利用Ｇａｕｓｓｉａｎ－９２从头算程序，在６－３１Ｇ￣＊基组下优化Ｐ_６（Ｄ_６ｈ）分子和Ｐ_（１２）（Ｄ_（６ｈ））原子簇，并进行了振动频率的计算．得到２Ｐ_６（Ｄ_（６ｈ））→Ｐ_（１２）（Ｄ_（６ｈ））总能量的相对值，即△Ｅ＝Ｅ_Ｐ_（１２_（Ｄ_（６ｈ））－２ＥＰ_６（Ｄ_（６ｈ））＝－１．１９７ｅＶ．　Ｐ_（１２）（Ｄ_（６ｈ））原子簇较２Ｐ_６（Ｄ_（６ｈ））分子在热力学上更为稳定。基组下，Ｈｐ＝ＨＰ优化的Ｐ＝Ｐ双键键长为０．２００５ｎｍ，Ｈ２Ｐ─ＰＨ２优化的Ｐ─Ｐ单键键长为０．２２１４ｎｍ，显然，Ｐ６（Ｄ６ｈ）分子中的键长比优化双键长０．００９１ｎｍ，比优化单键短０．０１１８ｎｍ，对于Ｐ６（Ｄ６ｈ）分子而言，其键长介于单、双键之间且相等。Ｐ６分子前线轨道的第３９条分子轨道形式估算为：联系人及第一作者：冯健男，男，２５岁，博士研究生。