OSW saponins: facile synthesis toward a new type of structures with potent antitumor activities

[reaction: see text] OSW saponins, featuring a 16beta,17alpha-dihydroxycholest-22-one aglycon and an acylated beta-D-xylopyranosyl-(1-->3)-alpha-L-arabinopyranosyl residue attached to the 16-hydroxyl group, have recently been discovered from a group of lily plants, which show potent antitumor activities with a novel mechanism of action. This paper describes an aldol approach to the stereoselective construction of the 16alpha,17alpha-dihydroxycholest-22-one structure from 16alpha-hydroxy-5-androsten-17-ones and propionates. Elaboration of the aldol adducts toward OSW-1, involving installation of the isoamyl ketone side chain, inversion of the 16-hydroxyl configuration, and selective protection of the C22-oxy function, has been explored and accomplished. In particular, the present route was found convenient for the synthesis of OSW saponin analogues with a C22-ester side chain. Thus, the 23-oxa-analogue of OSW-1 (40) was prepared starting from the industrial dehydroisoandrosterone (1) in a linear eight-step sequence and in 26% overall yield. Analogues with a variety of modified side chains were prepared, via aldol condensation with propionates of varying length, thiopropionate, and acetate (for preparation of 68-75) or via aminolysis of the 22,16-lactone 26 (for preparation of the 23-N-analogues). Cross metathesis (CM) reaction was also found feasible for modification at the final stage from C22-allyl ester 70. Valuable structure-activity relationships (SAR), together with the practical synthetic approach, have thus been provided to set a new stage for further studies on this new type of antitumor structures.     

龋病人牙釉质表面硬度及抗磨损性能测试

采用人工方法制成人牙釉质浅龋及使用抗龋措施的龋损釉质样本，分别测量各组釉质表面显微硬度，并以微动摩擦磨损试验机测试其抗磨性能，试验结果表明：各组实验组釉质较对照组表面硬度都有不同程度下降，氟化钠前处理会使釉质表达硬度显著下降，人工浅龋牙釉质的抗磨损性能不如正常釉质，使用两种抗龋措施对其抗磨性能没有明显改善。     

西印度蔗螟聚集信息素次要组份合成方法的改进

2-甲基-4-庚醇和2-甲基-4-辛醇是西印度蔗螟(Metamasiushemipterus)聚集信息素的次要组份，本文以天然产物(S)-亮氨酸为原料合成出了2-甲基-4-庚醇及2-甲基-4-辛醇的所有对映异构体，其关键步骤是由(2S)-4-甲基-1,2-戊二醇合成出(2S)和(2R)-4-甲基-1,2-环氧戊烷两种重要中间体，目标产物光学纯度可达95%以上。     

树枝状十二酯的合成

以乙二胺和丙烯酸十二酯为原料，甲醇为溶剂，采用迈克尔加成反应合成了低代的树枝状十二酯。探讨了反应条件对树枝状十二酯收率的影响。乙二胺2mL(30mmol)，n(乙二胺)：n(丙烯酸十二酯)=1：6，甲醇占反应液总体积的50％，反应温度40℃，反应时间48h，产率54．9％。     

邻苯二胺合钴氧合反应的研究Ⅰ 水溶液中配合物及其氧合配合物稳定常数的测定

自１９３８年Tsumaki报道犤１犦氧载体以来，这方面的研究已有很大进展犤２犦，只是理论研究居多。氧载体的氧合常数是氧载体研究中的一个重要参数，它的测定是氧载体研究中的一项重要内容，用pH电位法测定氧载体的氧合常数已有研究报道犤２～４犦，作者在研究中发现，邻苯二胺合钴（o－Phdn－Co）配合物在固相和水溶液中与O２反应时表现出很大差异，其反应产物的组成比分别为液相配合物Co∶O２＝２∶１，而固相配合物Co∶O２＝１∶２，为究其成因和进行理论探讨，有必要先测定其氧合常数。由于o－Phdn－Co配合物的配位常数也未见文献…     

Dependence of Performance of Organic Light-emitting Devices on Sheet Resistance of Indium-tin-oxide Anodes

IntroductionIndium-tin-oxide(ITO) has been widely used asthe anode material in organic light-emitting devices(OLEDs) because of its high transmittance in the visi-ble region and low electrical resistivity. In the pastyears, many investigations focused on …     

氰基乙烯基苯胺衍生物的电化学行为

本文利用循环伏安法研究了电子给-受体模型化合物——氰基乙烯基苯胺衍生物的电化学行为,并对推电子取代基团—NH_2和—N(CH_3)_2与吸电子取代基团氰基乙烯基对化合物电化学行为的影响进行了较为详细的讨论.提出了这些化合物的电氧化态和电还原态的结构,通过分析比较叔、仲和伯自由基对化合物电化学行为的影响,探讨了电极反应机理.     

Study on the dual-frequency oscillations in galactose-BZ system

Three types of dual-frequency oscillations in KBrO3-galactose-acetone-MnSO4-H2SO4 have been observed in a batch reactor depending on the initial concentration of H2SO4 or Br-. Similar phenomena were also observed when galactose was replaced by other aldosugars such as glucose, arabi-nose, lactose and maltose. However no dual-frequency oscillation has been found when ketosugar like fructose was used instead of galactose as the substrate. The roles of acidity, bromide ion and acetone in dual-frequency oscillations have been analyzed. The mechanism of dual-frequency oscillations has been discussed.     

Phase behaviour and microstructures of microemulsions (I)

By the orthogonal design, the optimal formation conditions for the middle-phase microemulsions in the system dioctadecyldimethylammonium chloride (DODMAC)/ sodium dodecyl sulfate (SDS)/n-butanol/n-hep-tane/brine were obtained as follows: W_DODMAC: W_SDS = 1:4-1:5,C _π-butanol (%) = 11.0-12.0, andC _NaCl (%) = 3.25 Investigations have been made on the effects of the concentrations of NaCl and n-butanol (l.0%-14.0%), the ratios ofWDODMAC: to W_SDS, and the kinds of alcohols (n-propanol, n-butanol, and n-pentanol) on the formation, the phase behaviour, the ultralow interfacial tensions, the optimal salinity (S^*), and the length of salinity (δS). Some rules and data were worked out about the formation and characteristics of the middle-phase microemulsions. The mi-crostructures of the middle-phase microemulsions were also studied by using FT-IR, ESR, and freeze fracture electron microscopy techniques. The results from the three methods show that the microstructures of the middlephase mi-croemulsions undergo the change from O/W to bicontinuous (B.C.) and to W/O. The distribution rule of the orga-nized molecule assemblies in the middle-phase microemulsions is conducible to constructing the model of microemulsion systems, to recognizing the microstructures of the middle-phase microemulsions, and to setting forth the relationship between the microstructures and macro-properties of rnicroemulsions. Project supported by the Niltional Natural Science Foundation of China and the Chinese Postdoctoral Science Foundation.     

新型树状大分子核醚-四硅烷的合成

以季戊四醇为原料合成了一种新型树状大分子核--醚-四硅烷,可用于树状大分子构筑.通过季戊四醇(1)与溴丙烯的醚化反应得到四烯丙基醚2,然后在Pt催化作用下,2与硅氯仿通过硅氢化反应生成醚-四(三氯硅烷) 3(可直接与多种官能团反应生成树状大分子),3经过LiAlH4还原后得到目标产物醚-四硅烷4.通过IR, 1H NMR, 13C NMR对中间体和目标产物的结构进行了表征,并对产物的结构进行了讨论和确认.