Regioisomers in Vorbrüggen''s guanine nucleoside synthesis; N9 selectivity with a glucosamine derivative and 2-N-acetyl-6-O-diphenylcarbamoylguanine

Vorbrüggen coupling of trimethylsilylated 2-N-acetylguanine with pentofuranose derivatives gives N7/N9 glycosyl mixtures. The N9 isomers can be obtained selectively with 2-N-acetyl-6-O-diphenylcarbamoylguanine, and even with a less reactive glucosamine derivative.     

Reaction Between 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione and <Emphasis Type="Italic">tert</Emphasis>-Butyl Isocyanide in the Presence of Primary or Secondary Amines

Summary. 5-Isopropylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (the condensation product of Meldrums acid and acetone) reacts smoothly with tert-butyl isocyanide in the presence of primary or secondary amines to produce N-tert-butyl-2,2-dimethylbutyramide derivatives and/or 1-tert-butyl-4,4-dimethyl-2,5-dioxopyrrolidine-3-carboxamides in good yields.     

双胍辛醋酸盐杀菌剂及其两种中间体的合成与生物活性

O-methylisourea acetate was synthesized by two procedures from the main raw materials including carbamide, dimethyl sulfate, acetic acid and concentrated sulfuric acid. Its content reaches 98 % and the total yield attains to 70%. 1, 17-Diamino-9-azaheptadecane was first synthesized by two procedures using sebcic acid, 1,8-octanediamine, sodium azide and concentrated sulfuric acid as the main raw materials. Its content reaches 98% and the total yield is 65%. The structure of both were confirmed by FT-IR, ^1H NMR and their available analysis method was established. Fungicide bis-(8-guanidino-octyl )amine acetate was synthesized from these two intermediates and its structure was confirmed by FT-IR and ^1HNMR. Fungicidal activity test showed that it is a kind of broad-spectrum fungicide with notably effect.     

景洪哥纳香和大叶紫玉盘化学成分研究

从景洪哥纳香和大叶紫玉盘根醇提物中，采用色谱分离方法，分别得到43个和 33个化合物，通过波谱技术和化学方法鉴定了这些化合物的结构。其中，从景洪哥 纳香根中得到1个新化合物，命名为8－乙酰基－9－去氧哥纳香吡喃吡喃酮（1）； 从大叶紫玉盘根中得到1个新化合物，命名为大叶素A（2）。另外，从景洪哥纳香 根中，还分离得到一个神经鞘胺醇苷成分混合物asteriacerebrosides (3)，并通 过GC－MS技术，鉴定了该混合物的脂肪酸部分（FAM）和长链胺部分（LCB）的种类 数目及碳链长度。结果表明，3中脂肪酸部分，含7个脂肪酸，碳链长度分别是16, 18, 19, 20, 21, 22和23个碳；其长链胺部分包含5个脂肪胺，对应链长度为21， 22，23，24和25个碳。     

Zur Präparation und Struktur gemischtvalenter Niob-Wolframoxide der Zusammensetzung (Nb,W)17O47

Preparation and Structure of Niobium Tungsten Oxides (Nb,W)₁₇O₄₇ with Mixed Valency The formal substitution of 2Nb⁵⁺ by Nb⁴⁺ or W⁴⁺, respectively, and W⁶⁺ leads to tungsten niobium oxides (Nb,W)₁₇O₄₇ with mixed valency. The phases Nb_8-nW_9+nO₄₇ with n = 1 to 5 could be obtained by heating (1 250°) mixtures of NbO₂ or WO₂, respectively, with Nb₂O₅ and WO₃. The products crystallize with the structure of Nb₈W₉O₄₇. This is proved by X-ray powder diffraction and transmission electron microscopy. A further decrease of the Nb-content results in two-phase products.     

Modified Coumarins. I. Synthesis of 5-Phenyl-7H-furo[2, 3-g]chromen-7-ones and 9-Phenyl-7H-furo-[2, 3-f]chromen-7-ones

5-Phenyl-7H-furo[2,3-g]chromen-7-ones and 9-phenyl-7H-furo-[2,3-f]chromen-7-ones, new analogs of psoralen and allopsoralen, are synthesized from 7-hydroxy- and 5-hydroxy-4-phenylcoumarins     

Condensation of 1-carbamoylmethyl-2,3,3-trimethyl-3H-indolium chloride with aromatic aldehydes

The reaction of 1-carbamoylmethyl-2,3,3-trimethyl-3H-indolium chloride with various aromatic aldehydes in acetic acid and the subsequent workup of the intermediate styrylic derivatives with strong bases yielded 9a-(2-arylethenyl)-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one derivatives. Condensation of the mentioned salt with salicylaldehyde in acidic or basic medium afforded the derivative of l-carbamoylmethylspiro[benzopyran-2,2-indole]. Alkylation of the latter compound with benzyl chloride in the presence of potassium hydroxide gave 9a-[2-(2-benzyloxyphenyl)ethenyl]-1,2,3,9a-tetrahydro-9H-imidazo[1,2-a]indol-2-one.Department of Organic Chemistry, Kaunas University of Technology, LT-3028 Kaunas, Lithuania Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 761–769, June, 2000.     

Determination Limit of Fluorescence Turn‐On Probes for the Acetate Anion

Three fluorescent turn‐on probes containing 3,6‐dichloro‐9H‐carbazole as carbazyl part have been designed and synthesized. Among studied anions F^?, AcO^?, H₂PO , Cl^?, Br^? and I^?, AcO^? showed the strongest binding ability with all probes. The strong basic anions, such as AcO^?, H₂PO , and F^?, induced a significant red‐shift in absorption and a concomitant increase in fluorescent emission of the probes caused by photoinduced electron transfer (PET). The determination limit of probe 3 (Scheme 1) toward AcO^? is 3.0×10^?7 M . ¹H‐NMR Titration experiments shed light on the nature of the interaction between the probes and the anions. Theoretical investigation further illustrated the possible binding mode in these host? guest interactions and the roles of molecular frontier orbitals in molecular interplay.     

Syntheses and Electrical Conductivities of 9-Fluorenone-Iodine-Alkali Iodide Complexes

A new series of 9-fluorenone-iodine-alkali iodide complexes (FIMI, M=Na, K, Rb or Cs) has been prepared from chloroform. These complexes yield needle-like crystals with metallic luster along the needle axis. The longitudinal dc conductivities at room temperature are in the order of 10^?3 to 10^?5 S cm^?1. They all have semiconductive properties with activation energies of about 0.4 to 0.7 eV. A significant result is that the conductivity varies systematically with the cation size. A decrease in the cation size results in an increase in the conductivity. Resonance Raman spectra show that iodine is present as a linear chain of symmetric I^?₃ units in these complexes. Infrared spectra of these complexes are discussed with an attempt to estimate the interaction between the alkali cation and the carbonyl group of 9-fluorenone.     

给体-受体体系分子内光致电子转移反应研究

对一类以9，10－二甲氧基蒽为给体，双酚A为连接链连接不同受体的电子给体－受体体系，通过单光子计数法测定荧光寿命，计算了各体系内的光致电子转移反应速率常数，通过测定氧化还原电位，计算出各电子给体－受体体系电子转移反应的自由能变化．并根据电子转移反应理论对光致电子转移速率常数与自由能变化关系进行了理论计算分析，发现本文各体系的光致电子转移速率常数的实验值与电子转移反应理论曲线吻合得比较好，同时也揭示在该类给体－受体体系中未出现电子转移反转区的原因在于电子转移过程自由能变化（－ΔG）没有足够大。