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《Tetrahedron: Asymmetry》1999,10(6):1119-1128
A systematic study of reactions between 5-substituted and 5,6-disubstituted (S)-2-p-tolylsulfinyl-p-benzoquinones and cyclopentadiene or trans-piperylene is reported. Complete regio and π-facial selectivities are observed. The different behaviours of cyclic and acyclic dienes in the presence of ZnBr2 (cyclopentadiene showed reversed diastereoselection) and the role of BF3·OEt2 are discussed. 相似文献
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《Tetrahedron: Asymmetry》1998,9(17):2965-2969
Enantiopure sulfinylnaphthoquinone (+)-1 reacted with racemic acyclic dienes 2a–f bearing a stereogenic allylic center, through a tandem cycloaddition/pyrolytic sulfenic acid elimination, to afford enantio-enriched compounds 4a–f and 5a–f with good like:unlike selectivities (ca. 75:25) and good enantiomeric excesses (68–82%), arising from the partial kinetic resolution of the racemic dienes. 相似文献
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CHI Guo-Chen② CHEN Ru-Yu② 《结构化学》2002,(1)
1 INTRODUCTION It is well known that natural and modified nucleosides have potential antiviral and anticancer activities[1,2]. These observations prompted us to synthesize the title compound -a new kind of spironucleoside, whose structure was determined by 1HNMR, 31PNMR and elemental analysis. The configuration was assigned by means of nuclear Overhauser effect. To further confirm the structure and configuration unambiguously, the title compound was subjected to X-ray diffractio… 相似文献
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Suitably functionalized alkylphenylsulfones have been used as building blocks for the synthesis of several modified side-chains steroids1. We describe here the synthesis of (S)-2-methyl and (2S)-2,3-dimethyl butyl phenylsulfones (4a) and (6), which can be used for the construction of the side chain of a few marine sterols2 or brassinosteroids3 as well. 相似文献
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The title compound, C15H22N3O9P·2H2O, Mr=455.36, crystallizes in orthorhombic, space group P212121, with a =9.193(2), b =14.681(3), c =15.201(3)A, V =2501(1)A3, Z =4, Dx=1.474g/cm3, λ(MoKα)=0.71073A, μ=0.1894mm-1, T=299±1K, F(000)=960, R=0.061 and Rw=0.068 for 1899 observed reflections with I≥3σ(I). The analysis results indicate that the title compound is of lyxo-configuration and the configuration at C4″ is S. In the crystal state the molecule has anti conformation about glycosidic bond with the torsion angle-151.7°, the sugar ring is puckered with C3′-endo-C2′-exo, and the conformation of the C4′-C5′ bond is-sc. 相似文献
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为了检验Davidson和Clark的局部自旋原理对铁硫蛋白簇合物的可行性,[Fe2S2(SR)4]2-(R=-H,-CH3)模型被选为研究对象.该目的可通过计算这些体系的局部自旋期望值〈SA.SB〉,〈S2A〉和mA,并讨论它们与Heisenberg自旋模型(HSM)和Noodleman对称破缺理论之间的联系来实现.在具体的计算中采用了自旋非限制Hartree-Fock(UHF)和自旋极化密度泛函(Spin-polarized DFT)方法,同时比较它们的计算质量.此外,采用多种方案计算了它们的交换耦合常数,并同前人的结果作了比较. 相似文献
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4-(S)-[2-(N-甲基)吗啉基 ]-5-(R )-(l-薄荷烷氧基 )-丁内酯结构分析 总被引:1,自引:0,他引:1
N-甲基吗啉对5-(l-薄荷烷氧基)-2(5H)-呋喃酮的光催化不对称共轭加生成了4-(S)-[2-(N-甲基)吗啉基]-5-(R)-(l-薄荷烷氧基)-丁内酯,在四氢呋喃(THF)对比实验、参比物^13CNMR对照及不同溶剂^13CNMR测定的基础上,该新化合物的结构用高分辨率的子核磁共振谱、碳核磁共振谱、质谱、红外光谱及元素分析、旋光度等数据进行了确证。 相似文献
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The syntheses of poly(methylsiloxane)s containing 4-[S(-)-L-methyl-1 -butoxy] -4′-[p-(ω -alkan -1 -yloxy)benzoyloxy] -a-methylstilbene side groups containing 11-undecanyl (18), 8-octyl (19), 6-hexyl (20), and 3-propyl (21), of a poly[(50-55%)-methyl-co-(45-50%)-dimethylsiloxane] containing 4-[S(-)-2-methyl-1-butoxy]-4′-[p-(8-octan-1-yloxy)benzoyloxy]-α-methylstilbene side groups (22) and of a poly(methylsiloxane) containing a 1:1 molar ratio of 4-[S(-)-2-methyl-1 -butoxyl]-4′ -[p-(8-octan-1 -yloxy)benzoyloxy] -α-methylstilbene and 4-[S(-)-2-methyl-l -butoxyl-4′ -[p-(6-hexan-1-yloxy)-benzoyloxyl-α-methylstilbene side groups (23) are described. All polymers and copolymers were characterized by a combination of differential scanning calorimetry and thermal optical polarized microscopy techniques. 18 exhibits an enantiotropic S A, while 19, 20, 21, and 23 display both enantiotropic s A and S*c mesophases. 22 exhibits only an enantiotropic s: mesophase. In addition, all polymers and copolymers exhibit sidechain crystallization. These results have demonstrated that extending the length of the rigid part of the mesogenic unit of 4-[S(-)-2-methyl-l-butoxy]-4′-(ω-alkan-l-yloxy)-α-methylstilbene to 4-[S(-)-2-methyl-l-butoxy]-4′ -[p-(ω-alkan-l -yloxy)benzoyloxy]-α-methylstilbene increases the tendency of the resulting poly(methylsiloxane)s toward polymesomorphism. 相似文献
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Yi Bo ZHOU Jun An MA Li Xin WANG Qi Lin ZHOU* State Key Laboratoratory Institute of Elemento-Organic Chemistry Nankai University Tianjin 《中国化学快报》2002,13(10)
During the last decade, 1-aminocyclopropanecarboxylic acid and its derivatives (ACCS) have attracted increasing attention of organic and bioorganic chemists due to their outstanding biological properties, ranging from antimicrobial, insecticidal, plant growth and fruit ripening controls, etc.1. Moreover, the three-membered carbocycle provides building blocks of unprecedented synthetic potential because it undergoes selective ring opening, ring enlargement or cycloaddition reactions2. The mo… 相似文献
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以高藜芦胺为起始原料,经N-磺酰化反应制得高藜芦磺酰胺(2);2分别与芳乙烯甲醚经对甲苯磺酸催化的Pictet-Spengler反应后用金属钠脱除Ts基团合成了(±)-norlaudanosine(5a)和(±)-O,O-dimethylcoclaurine(5b);使用半量拆分法,以N-乙酰-L-苯丙氨酸为拆分剂,制得(S)-(-)-5a和(S)-(-)-5b,其结构经1H NMR,13C NMR,IR,MS和HR-ESI-MS确证。 相似文献
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苄氧乙基环氧乙烷;不对称合成;由(S)-和( R )-天冬氨酸合成( R )-和(S)-(2-苄氧乙基)环氧乙烷的改良方法 相似文献
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《合成通讯》2013,43(22):3913-3917
Abstract Aβ2,β3-homoproline derivative, (2S, 2′S)-3-phenyl-2-(pyrrolidin-2′-yl)propionic acid, was synthesized starting from l-proline. After preparation of the (4S, 4aS)-4-benzyl-4a,5,6,7-tetrahydro-pyrrolo-[1,2-c]pyrimidine-1,3-dione under a mild condition, the absolute configuration of target compound was assigned using 2D H-H COSY and H-H NOESY technologies. 相似文献
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YU An-Guang WANG Nai-Xing ZHANG Jun-Ping YANG Yun-Xu WANG Wu-Wei SHENG Rui-Long 《有机化学》2004,24(Z1):31-32
Benzopyran compounds possess diverse pharmacological properties such as β-blockade, anticonvulsant and antimicrobial.[1,2] Our interest has been focused on the synthesis of 1-[6-Fluoro-2S]-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (6) and 1-[6-fluoro-(2R)-3H,4H-dihydro-2H-2-chromenyl]-(1R)-1,2-ethanediol (7) which are particularly convenient precursor to (S,R,R,R)-NE (8). 8 containing four asymmetrical carbon atoms was reported to be the most active isomer.[3] Chandrasekhar[4] has reported on the synthesis of 8. The key step to synthesize this compound is to obtain the chiral chromanone 6 and 7. 6 was accomplished in 8 steps by the Clasien rearrangement and a one-pot Sharpless asymmetric epoxidation, but the compound 7 was accomplished in 10 steps. Johannes[5] used Zr-catalytic kinetic resolution of allylic ethers and Mo-catalyzed chromene formation to synthesize 8 in 14 steps. However both of the methods request many synthetic steps and expensive reagents. 相似文献
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Introduction1,4 Diazabicyclo[2 .2 .2 ]octane (DABCO)wasre portedtocatalyzeorganicreactionsduetoitsstrongbasici ty .1,2 Severalchiraltrans 2 ,3 disubstitutedDABCOshavebeensynthesizedandappliedtotheasymmetricBaylis Hillmanreaction3andvicinalhydroxylation .4ThefirstsynthesisofthetitlecompoundwasreportedbySoai5from (2S ,5S) bis(phenylmethyl)piperazine (1) ,asshowninScheme 1.Butthisprocedureislengthy ,andtheoverallyieldisnotsosatisfactory .Besides ,thereport edmethodforthepreparationof 1is… 相似文献