Effects of molecular structures on the olfactory responses of phospholipid membranes to four alcohols

In order to understand the relationship between phospholipid molecular structures and their olfactory responses to odorants, we designed and synthesized four phosphatidylcholine analogues with different long hydrocarbon (CH) chains and selected three natural phospholipids with different head-groups. By using interdigital electrodes (IEs) as olfactory sensors (OSs), we measured the responses of the Ifs coated with these seven different lipid membranes to four alcohol vapors in a gas flow system. The Ifs voltage changes were recorded and the voltage-relative saturate vapor pressure (V-P/P degrees) curves were also plotted. It was found that with a methyl (-CH3) placed at the C-8 position in the 18-carbon chain, the olfactory responses could be improved about ten times and with conjugated double bonds (C=C) in the long chains, the sensitivity could be increased by 3 similar to 4 orders of magnitude. As to head-groups, choline is preferred over ethanolamine and serine in phospholipid structures in terms of high olfactory sensitivity: These results are expected to be useful in further designing and manufacturing lipid-mimicking OSs. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.

6-(1H-吲哚-3-甲基)-5-乙基-3H-嘧啶-4-酮类化合物的合成及抗HIV活性研究

基于二氢烷氧苄基嘧啶酮(DABO)类非核苷类逆转录酶抑制剂(NNRTIs)的构效关系研究,设计合成了2个新的6-(1H-吲哚-3-甲基)-5-乙基-3H-嘧啶-4-酮类化合物,并采用C8166细胞进行了体外抗HIV活性测试,为新型S-DABO类非核苷类逆转录酶抑制剂结构修饰提出了新的设想.

毛蕊异黄酮类似物的合成及其对JAK/STAT信号途径调控的构效关系研究

干扰素（IFNs）是最早发现的具有广泛用途的一类细胞因子，IFN-α通过JAK/STAT信号途径调控机体一系列生理和病理反应。至今尚未发现类干扰素的小分子。我们前期研究发现天然产物毛蕊异黄酮可激活干扰素诱导的JAK/STAT信号途径。为发现类干扰素小分子、获得小分子探针，本课题拟建立成熟的JAK/STAT信号途径的筛选模型，合成毛蕊异黄酮及其类似物，研究这些化合物的构效关系，进而尝试通过共价键标记生物素或香豆素来直接研究它们与相关受体的作用。 从异香草醛出发经7步合成反应得到了毛蕊异黄酮。采用平行合成策略得到异黄酮类化合物；采用分支式合成策略，以取代苯乙酸作为合成砌块，获得具有与异黄酮类似结构的香豆素、3-芳基喹诺酮。与分离得到的黄酮类化合物，构建了一个包括异黄酮、黄酮、香豆素、3-芳基喹诺酮在内的化合物库。 建立了包含IFN-α刺激反应元件 (ISRE)的荧光素酶报告基因体系，通过筛选化合物库中的化合物，发现异黄酮骨架为激活JAK/STAT信号途径必须结构、毛蕊异黄酮7-位酚羟基被取代后活性丧失。根据以上结果，对毛蕊异黄酮3′-位标记物的合成进行了初步尝试。 发现山茱萸科植物青荚叶(Helwingia japonica (Thunb.) Dietr.)有抑制蛋白酪氨酸磷酸酯酶1B（PTP1B）的活性。从其地上部分95%乙醇提取物的乙酸乙酯部分分离得到5个化合物,应用波谱方法及与已知品对照的手段鉴定它们为p-menth-2-en-1β, 4β, 8-triol (Z-1)、blumenol A (Z-2)、2′,3′,4′,5′,6′-五羟基查尔酮(Z-3)、洋芹素7-O-β-D-吡喃葡萄糖苷(Z-4)、木犀草素7-O-β-D-吡喃葡萄糖苷(Z-5). Interferons (IFNs) are one kind of cytokines with broad functions. IFN-α mediates series physiological and pathological changes of human body via JAK/STAT pathway. Untill now, no IFNs-like small molecules are discovered. In our preliminary experiment, the natural product calycosin has been observed to activate JAK/STAT pathway. Therefore, we establish a luciferase reporter gene system and synthesize calycosin and its analogues to reveal their structure-activity relationship (SAR). Besides, in order to prove that calycosin activates JAK/STAT pathway through IFN receptor, we attempted to tag it with biotin or coumarin by covalent bonding. Calycosin was synthesized from isovanillin via seven steps. Other isoflavones were obtained by parallel synthesis; coumarins and quinolones were prepared through divergent synthesis, using substituted phenylacetic acids as building blocks. Combing with natural flavones, a small molecule library was established. A luciferase reporter gene system, consisting of 5 copies of the ISRE (interferon-stimulated response element), was used for screening of small molecules from that library. We found that the core-structure of isoflavone was necessary, and if the 7-OH is substituted, the activity slumps. According to our observation, we tried to tag biotin or coumarin at 3′-OH of calycosin. The 95% ethanol extract of the aerial parts of Helwingia japonica (Thunb.) Dietr. showed protein tyrosine phosphatase 1B (PTP1B) inhibitory activity. Five compounds were isolated. On the basis of spectral data or by comparison with authentic samples, they were identified as p-menth-2-en-1β,4β,8-triol (1), blumenol A (2), 2′,3′,4′,5′,6′-pentahydroxychalcone (3), apigenin 7-O-β-D-glucopyranoside (4), and luteolin 7-O-β-D-glucopyranoside (5).

具有环氧化酶-2选择性抑制活性的多取代蒽醌的合成

1-甲基-2-甲氧羰基-3, 6, 8-三羟基-7-甲氧基蒽醌是从唐菖蒲干球茎中分离到的具有环氧化酶-2选择性抑制活性的多取代蒽醌类化合物。本文试图合成该化合物，实现了其类似物的合成，同时发现了几个未见报道的反应。 1．通过Diels-Alder 反应合成了关键中间体——3-甲基-5-羟基-1, 2, 4-苯三甲酸三甲酯，1-COOMe选择性水解产物与1, 2, 3-三甲氧基苯进行分子间Friedel-Crafts反应的产物再进行分子内Friedel-Crafts反应得到了目标产物的类似物1-甲基-2-甲氧羰基-3-羟基-6，7，8-三甲氧基蒽醌（路线1）。目标产物及其它类似物的合成正在进行中。 2．以乙酰乙酸甲酯和巴豆醛为原料，经过Michael加成、分子内的Aldol反应、芳香化、选择性甲酰化和还原反应，得到关键中间体2-甲基-3-羟甲基-6-甲氧基苯甲酸甲酯及其衍生物。通过该化合物与3，4，5-三甲氧基苯甲酸甲酯进行Friedel-Crafts烷基化反应得到了多取代的二苯基甲烷衍生物，拟进一步关环合成目标化合物（路线2）。 3．发现邻甲氧基苯甲酸甲酯中酯甲基可以被正丁基锂和仲丁基锂中烷基交换生成相应的酯，反应的机理不明确。当使用叔丁基锂时，得到的是邻甲氧基苯基叔丁酮，这个方法可以用来合成芳基叔丁酮类化合物。 4．以2-苄氧基-6-甲基苯甲酸甲酯为原料进行氯甲基化反应时，以苯和二氯乙烷作溶剂，发生了苄基的迁移和芳环的偶联，分别得到2，2'-二甲基-3，3'-二甲氧羰基-4，4'-二羟基联苯和2，2'-二甲基-3，3'-二甲氧羰基-4，4'-二羟基-5，5'-二苄基联苯。这是对称联苯合成的新方法。 5．水杨酸羟基邻对位的选择性甲酰化可以分别通过水杨酸和水杨酸甲酯用HMTA/CF3COOH来实现。 6．Lewis酸催化3，4，5-三甲氧基苄醇环化成1, 2, 3, 6, 7, 8, 11, 12, 13-nonamethoxyl-10,15-dihydro-5H-trbibenzo [a, d, g] cyclononene (NDTC)，产率(54%)高于已有方法（12%）。 Methyl 3,6,8-trihydroxy-7-methoxy-1-methylanthraquinone-2-carboxylate is a new COX-2 selective inhibitor isolated from Gladiolus gandavensis. Two strategies were investigated to synthesis this compound, in which some important reactions were discovered. 1. The key intermediate 5-hydroxy-3-methylbenzene-1,2,4-tricarboxylic acid 2,4-dimethyl ester was prepared via Diels-Alder reaction followed by selective hydrolysis of 1-COOMe. This compound was coupled with 1,2,3-trimethoxybenzene and the product undergo intramolecular Friedel-Crafts reaction to give methyl 3-hydroxy-5,6,7-trimethoxy-1-methylanthraquinone-2-carboxylate (1st route). The target compound and other analogues are being prepared with the same procedure. 2. The key intermediates methyl 3-hydroxymethyl-6-methoxy-2-methylbenzoate and its derivatives were prepared starting from crotonaldehyde and methyl acetoacetate via Michael addition, intramolecular aldol reaction, aromatization, formylation and reduction. The intermediates were coupled respectively with derivatives of gallic acid to give polysubstituted diphenylmethane. However, attempts to cyclize these compounds to the target compounds and analogues were not successful (2nd route). 3. In the process for ortho-lithiation of methyl 2-methoxybenzoate, the substrate converted respectively to n-butyl 2-methoxybenzoate and sec-butyl 2-methoxybenzoate when n-BuLi and sec-BuLi were used. However, tert-BuLi reacted with methyl 2-methoxybenzoate afford 2-methoxyphenyl tert-butyl ketone, which could be used to synthesize aryl tert-butyl ketones. 4. The transformtion of methyl 2-benzoxy-6-methylbenzoate to dimethyl 4,4'-dihydroxy-2,2'-dimethylbiphenyl-3,3'-dicarboxylate in benzene, and dimethyl 5,5'-dibenzyl-4,4'-dihydroxy-2,2'-dimethylbiphenyl-3,3'-dicarboxylate in 1,2-dichloroethane in the presence of ZnCl2 provides a new method for the synthesis of symmetric biphenyl. 5. The formylation of salicylic acid at C-5 and methyl 2-hydroxybenzoate at C-3 could be regioselectively realized by using HMTA/CF3COOH. 6. Racemic 1, 2, 3, 6, 7, 8, 11, 12, 13-nonamethoxyl-10, 15-dihydro-5H-trbibenzo [a, d, g] cyclononene was prepared via Lewis acids catalyzed trimerization of 3, 4, 5-trimethoxylbenzyl alcohol with yield (54%) higher than the reported procesure (12%).

手性有机小分子路易斯碱催化剂的设计、合成及其在亚胺不对称还原中的应用

手性胺是合成天然产物和手性药物的重要中间体，亚胺的不对称催化还原是制备光学活性手性胺的最直接有效的方法之一。但是，由于C＝N双键的反应活性较弱以及容易发生E/Z异构等问题，亚胺的不对称催化还原具有很大的挑战性，既具有高对映选择性又具有宽广底物普适性的催化剂很少。 本文分别由手性脯氨酸、哌啶酸、哌嗪酸以及氨基醇出发，设计和合成了一系列结构新颖、合成简便、性能优良的酰胺类有机小分子路易斯碱催化剂，以廉价的三氯氢硅为氢源，用这些催化剂催化亚胺不对称还原，得到了非常优良的收率、对映选择性和前所未有的底物普适性。 文献研究认为，除N-甲酰基外，分子内含有芳香酰胺是能催化亚胺还原的有机小分子路易斯碱催化剂具有较高对映选择性的必要条件，我们研究发现N-甲酰脯氨酸非芳香酰胺类催化剂（包括结构简单的C2-对称型脯氨酰胺类催化剂），对N-芳基酮亚胺的还原可获得达86%的对映选择性，远高于同类芳香酰胺催化剂，证明N-甲酰非芳香酰胺类路易斯碱催化剂在亚胺还原中也能得到高的对映选择性。 在进一步研究中，我们以手性六元哌啶酸为模板，分别设计合成了N-甲酰哌啶酸芳香酰胺和N-甲酰哌啶酸非芳香酰胺两类催化剂，其中芳香酰胺催化剂（S）-N-（甲酰基）哌啶-2-酸-1-萘基酰胺（28）和非芳香酰胺催化剂（2S,1'S,2'S）-N-（甲酰基）-哌啶-2-酸（1',2'-二苯基-2'-乙酰氧基-乙基）酰胺（30）显示出非常优良的催化活性和对映选择性，对于N-芳基芳香酮亚胺的还原，无论是缺电子体系还是富电子体系，绝大部分都能得到很高的收率（达98%）和对映选择性（达96% ee)。特别值得一提的是30对一些脂肪族亚胺和α,β-不饱和亚胺的还原，虽然底物为E/Z混合物，也能得到很高的收率（达93%）和对映选择性（达95% ee)，这样的底物普适性在过渡金属催化体系中也是前所未有的。 现有的催化亚胺还原的高对映选择性催化体系大多仅适用于甲基酮亚胺底物，对位阻较大的非甲基酮亚胺很难获得好的结果。我们以L-哌嗪酸为模板设计和合成出的（S）-N-（甲酰基）-哌嗪-2-酸-4-对叔丁基苯磺酰基-苯基酰胺不但对N-芳基甲基酮亚胺有很好的对映选择性（达90% ee)，而且对于大位阻的N-芳基非甲基酮亚胺有更好的对映选择性（达97% ee)。该催化剂与30在底物普适性方面具有很好的互补性。 我们还设计了基于1,2-二苯基氨基醇为模板的新型N-甲酰路易斯碱有机小分子催化剂，首次发现结构简单的N-甲酰（1S,2R）二苯基氨基醇能较好的催化N-芳基酮亚胺，最高可以得到82%的对映选择性。 针对我们设计合成的结构新颖、性能优良的催化剂，我们对催化机理进行了探讨和解释，提出了几个假想的机理模型。 Catalytic enantioselective reduction of imines represents one of the most straightforward and efficient methods for the preparation of chiral amines, an important intermediate for the synthesis of natural products and chiral drugs. However, asymmetric reduction of imines remains a big challenge and highly enantioselective catalysts with a satisfactorily broad substrate scope remain elusive. Factors contributing to the difficulty of this transformation include the weak reactivity of the C=N bond and the existence of inseparable mixtures of E/Z isomers. Starting from chiral proline, pipecolinic acid, piperazine-2-carboxylic acid and 1,2-diphenyl amino alcohol, a series of structurally simple and easily prepared amides were developed as highly effective Lewis basic organocatalysts for the asymmetric reduction of imines with trichlorosilane as the reducing agent, which promoted the reduction of N-aryl imines with high yields and excellent enantioselectivities with an unprecedented substrate spectrum. In the literature, it has been believed that besides the N-formyl group, the existence of an arylamido group in the structure of Lewis basic organocatalysts is a prerequisite for obtaining high enantioselectivity in the catalytic reduction of imines. However, we found that the N-formyl-L-prolinamides bearing non-arylamido groups, including structurally simple C2-symmetric tetraamides, could also work as effective Lewis basic catalysts to promote the asymmetric reduction of ketimines with high enantioselectivities (up to 86% ee), which are even more enantioselective than the analogues with arylamido groups. In further studies, we developed novel N-formamides with arylamido groups and non-arylmido groups as Lewis basic catalysts using the commercially available L-pipecolinic acid as the template. The catalysts (S)-1-formyl-piperidine-2-carboxylic acid naphthylamide 28 and (2S,1'S,2'S)-acetic acid 2-[(1-formyl-piperidine-2-carbonyl) -amino]-1,2-diphenyl-ethyl ester 30 were found to promote the reduction of a broad range of N-aryl imines in high yields (up to 98%) and excellent ee values (up to 96%) under mild conditions. Furthermore, catalyst 30 also exhibited high enantioselectivities (up to 95% ee) for the challenging aliphatic ketimines and α,β-unsaturated imines despite that these imines exist as E/Z isomeric mixtures. The broad substrate spectrum of this catalyst is unprecedented in catalytic asymmetric imine reduction, including transition-metal-catalyzed hydrogenation processes. Many of the currently available highly enantioselective catalytic systems only tolerate methyl ketimines, which gave poor results for bulkier non-methyl ketimines. Starting from L-piperazine-2-carboxylic acid, we developed (S)-4-(4-tert- butylbenzenesulfonyl)-1-formyl-N-phenyl-piperazine-2-carboxamide as highly enantioselective Lewis basic catalysts for the hydrosilylation of both methyl ketimines and steric bulky non-methyl ketimines. Moreover, higher enantioselectivities were obtained for non-methyl ketimines than methyl ketimines under the catalysis of this catalyst. Thus, this catalyst system complements with 30 in terms of the substrate scope. We also found that easily accessible (1R,2S)-N-formyl-1,2-diphenyl- 2-aminoethanol worked as an effective Lewis basic catalyst in the enantioselective hydrosilylation of ketimines, affording high enantioselectivities (up to 82% ee) for a broad range of ketimines. To rationalize the high efficiencies of the structurally novel catalysts we developed, several catalytic models have been proposed.

N-烷基氮杂糖及其衍生物的合成

多羟基哌啶类化合物通常称为氮杂糖，由于与糖结构的相似性，亚胺基环醇表现出强的糖苷酶和糖基转移酶抑制活性，可调控在生物识别及酶结构控制中起到重要作用的糖蛋白的生物合成与水解。因此这类抑制剂有望成为与糖代谢紊乱有关的疾病的治疗药物，如：抗糖尿病、抗肿瘤、抗溶酶体贮积症及抗病毒感染（包括艾滋病）等药物。正是由于氮杂糖的重要生物活性及诱人的药用开发前景，近年来，有关氮杂糖及其衍生物的合成、生物活性及应用研究备受关注。 本论文探索了一系列的作为潜在的迈克加成中间体1-C-乙酰甲基/甲氧羰基甲基-5-N-取代呋喃核糖碳苷衍生物在碱的作用下先发生β-消除反应，接着发生分子内的迈克加成反应生成1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物及1-C-甲氧羰基甲基-N-取代氮杂吡喃糖碳苷衍生物的方法，该转变过程为先通过β-消除得到非环状的α/β不饱和共轭酮或酯的中间体，接着5-N-取代氨基与分子内的α/β不饱和共轭酮或酯发生分子内的1,4-亲核加成，其中，2'-酯的环加成立体选择性的得到β型1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物，而2'-酮的环加成得到立体异构体1-C-乙酰甲基-N-取代氮杂吡喃糖碳苷衍生物。此外，该类N-取代氮杂吡喃糖碳苷衍生物进一步脱除保护基，得到了一系列新的N-取代氮杂吡喃糖衍生物，拓展了氮杂吡喃糖碳苷分子库。 中间体1-C-(2'-oxoalkyl)-5-N-alkylated glycoribofuranoside的合成是由核糖为原料，通过对其结构修饰，在C-5氮原子上先引入不同的取代基，在C-1上引入乙酰甲基或甲氧羰基甲基。C-5取代氨基的引入通过两种方法：(a) 5-取代链状脂肪氨基可由链状的伯胺直接与5-甲磺酰基发生SN2亲核取代得到；(b) 5-取代芳香氨基可通过芳香醛与C-5氨基缩合再由硼氢化钠还原得到。2'-酰基的引入通过烯丙基氧化得到：2'-酮羰基由醋酸汞和琼斯试剂氧化得到；2'-酯基由高锰酸钾氧化再碘甲烷的作用下得到。 The polyhydroxylated piperidines, commonly be called azasugars. Iminocyclitols and their derivatives have exhibited remarkable biological activity to inhibit glycosidase-processing enzymes, with resulting potential chemotherapeutic applications against diabetes, cancer, lysosomal storage disorders and viral infections including AIDS. Recently, because of the important biological activity and excellent foreground on pharmaceutical application, great attention has been attracted to the synthesis of the new derivatives and analogues. In this dissertation, 1-C-(2'-oxoalkyl)-5-N-substituted-glycoribofuranosides, which used as latent substrates for intramolecular hetero-Michael addition, were converted to 2-ester and 2-ketone aza-C-glycopyranosides by base treatment. The transformation was achieved through β-elimination to an acyclic α/β-conjugated ketone or ester, followed by an intramolecular hetero-Michael addition by the 5-N-alkylated amino group. The 2-ester cycloaddition was highly stereoselective in favor of an equatorial 1-C-substitution while the 2-ketone cycloaddition was produced a pair of stereoisomers of 2′-ketonyl aza-C-glycoside. Additionally, the resultant different N-alkylated aza-C-glycopyranosides could be further prepared for various azasugar library constructions by removal of protecting groups. Synthesis of the key intermediate 1-C-(2'-oxoalkyl)-5-N-alkylated glycoribo- furanoside involved the introduction of 5-substituted amino and 1-C-2′-oxoalkyl groups from D-ribose. The 5-alkylated amino was introduced through two methods: (a) the 5-aliphatic series amino synthesized by the nucleophilic substitution of 5-mesylate using neat ethylamine, propylamine, butylamine, and hexylamine, (b) the 5-aromatic series amino synthesized by various aromatic aldehydes with C-5 amino under NaBH4 reduction. The 1-C-2′-oxoalkyl groups were introduced through oxidation of the ally group: the 1-C-allyl group was oxidized with Hg(OAc)2 and Jones reagent to the 2-ketonyl C-glycoside; the 1-C-allyl group was oxidized with KMnO4 and CH3I/NaHCO3 to 1-C-methyl acetate glycoside.

吲哚生物碱Desbromoarborescidine A 的全合成及烯胺C-亚磺酰化反应研究

从新几内亚核桃木的树皮中分离得到的吲哚类喹诺里西定生物碱10-Desbromoarborescidine A，因发现其具有阻滞钙离子通道的活性而倍受关注。10-Desbromoarborescidine A由A、B、C、D四个环组成，只有一个手性中心，是吲哚生物碱中结构较简单的一种，常作为此类生物碱全合成方法的模型化合物。但迄今为止，能高效而简便的实现手性10-Desbromoarborescidine A不对称全合成方法线路不多，大多数以不对称诱导的方式建立其手性中心，手性催化的方式仅有一例金属催化。从逆合成分析可知，Desbromoarborescidine A的全合成可以通过亚胺不对称催化还原进行关键的手性中心构建，而本课题组在之前的研究中通过手性有机小分子催化剂的发展，已将三氯硅烷氢转移还原亚胺发展成了一类简便实用、高效、高对映选择性并具有优良底物适应范围的不对称催化反应，我们希望以这一反应作为关键手段，发展一条Desbromoarborescidine A及其类似物不对称合成新路线。 根据我们设计的新路线，首先成功合成了其关键中间体，然后我们进行了关键的不对称催化尝试。用本实验室已有的高性能有机小分子催化剂虽得到了较好的对应选择性，但是产率很低。同时，为了验证整条线路的可行性，我们也用消旋的中间体进行拉通线路的尝试。但不幸的是，在脱除保护基时遇到了很大困难。尝试换不同的保护基，或改变脱保护基的顺序，都未能成功合成目标产物。究其原因可能是由于吲哚的特殊性造成的，吲哚类亚胺与常规的芳香亚胺有较大的差异，其NH基团无论保护还是不保护，对与其2位相联接的C=N双键均有很大的影响，导致其不对称催化还原难以进行。另外，由于所设计的还原产物含有处在吲哚苄位的胺基，稳定性较差，造成保护基脱除困难。 烯胺C-亚磺酰化反应是本课题组最近发现的一个新反应，之前未见文献报道。本研究对该反应进行了反应条件优化和底物扩展，发现带Cbz，Ac，COt-Bu，CO2Et，Bz等保护基的一系列环状和非环状烯胺在亚磺酸钠、DMAc和MeSiCl3的共同作用下能高效高产率生成β-胺基烯基亚砜类新化合物，为合成多官能团化的烯基亚砜新化合物提供了一条简便实用的途径。 The main constituent of Dracontomelum mangiferum B1, indoloquinolizidine alkaloid 10-Desbromoarborescidine A, has drawn great attention due to its calcium channel blocking activity. Its molecular structure is relatively simple compared with the other alkaloids of the same type, which has only one chiral center, albeit with four cycles A, B, C, and D. This compound is often used as a model target for exploring different strategies for the total synthesis of indole alkaloids. Nevertheless, so far there still lack practical and highly efficient methods for the asymmetric total synthesis of 10-Desbromoarborescidine A. Most of the current available methods rely on stoichiometric asymmetric synthesis for the construction of the chiral center. There is only one example reporting utilization of asymmetric catalysis, but with transition metal complex as the catalyst. Our retrosynthetic analysis shows that catalytic asymmetric reduction of imine could be used as the key step for the construction of the chiral center of Desbromoarborescidine A. Since in the previous studies our group has developed the asymmetric reduction of imines by trichlorosilane into a practical and highly efficient and enantioselective method using newly designed chiral organocatalysts, we hope to apply this method to develop a novel synthetic route for the total synthesis of Desbromoarborescidine A and its analogues in this study. According to the newly designed synthetic route, we first accomplished the synthesis of the key intermediates which was then examined for the critical asymmetric catalysis. The asymmetric reduction using the highly efficient organocatalysts, developed in our lab afforded high ee but poor yield. We tried different reaction conditions to improve the yield, but failed to get any good results. Simultaneously, to vertify the feasibility of the synthetic route we designed, we also tired to go through the route toward the racemic synthesis of Desbromoarborescidine A. But unfortunately, protection and deprotection proved to be big hurdles. All the different protection groups and different sequences of protection and deprotection we tried failed to get us through the designed synthetic sequence and furnish the final product. Most likely, the indole part is the culprit behind the failures.The NH group of the indole, no matter protected or not, may impact the catalytic asymmetric reduction of C-N double bond connected with 2-C. Additionally, the reduction product we designed contains an amino group in the β-position of the indole, which may cause problems due to its instability. C-sulfenylation of enamines is a novel reaction discovered recently by our group, which has not been seen before in the literature. In this study, optimization of the reaction conditions and exploration of the substrate scope were further undertaken for this reaction, which reveal that a series of enamines with N-Cbz, Ac, COt-Bu, CO2Et protection groups could all undergo smooth C-sulfinylations with the comined use of sodium benzene sulphinate, DAMc and MeSiCl3, efficiently furnishing the β-amino vinylsulfoxide products in high yield, affording a practical and highly efficient methods for synthesis of functional vinylsulfoxides.

Band Gap Tunable, Donor-Acceptor-Donor Charge-Transfer Heteroquinoid-Based Chromophores: Near Infrared Photoluminescence and Electroluminescence

A series of D-pi-A-pi-D type of near-infrared (NIR) fluorescent compounds based on benzobis(thia diazole) and its selenium analogues were synthesized and fully characterized by H-1 and C-13 NMR, high-resolution mass spectrometry, and elemental analysis. The absorption fluorescence, and electrochemical properties were also studied. Photoluminescence of these chromophores ranges from 900 to 1600 nm and their band gaps are between 1.19 and 0.56 eV.

Dye-Sensitized Solar Cells with a High Absorptivity Ruthenium Sensitizer Featuring a 2-(Hexylthio)thiophene Conjugated Bipyridine

We conjugated 2-(hexylthio)thiophene with bipyridine to construct a new heteroleptic polypyridyl ruthenium sensitizer exhibiting a charge-transfer band at 550 nm with a molar extinction coefficient of 18.7 x 10(3) M-1 cm(-1). In contrast to its analogues Z907 and C101, a mesoporous titania film stained with this new sensitizer featured a short light absorption length, allowing for the use of a thin photoactive layer for efficient light-harvesting and conversion of solar energy to electricity. With a preliminary testing, we have reached 11.4% overall power conversion efficiency measured at the air mass 1.5 global conditions. Transient photoelectrical decays and electrical impedance spectra were analyzed to picture the intrinsic physics of temperature-dependent photovoltage and photocurrent.

Reversible addition-fragmentation chain transfer mediated radical polymerization of asymmetrical divinyl monomers targeting hyperbranched vinyl polymers

Reversible addition-fragmentation chain transfer (RAFT) mediated radical polymerizations of allyl methacrylate and undecenyl methacrylate, compounds containing two types of vinyl groups with different reactivities, were investigated to provide hyperbranched polymers. The RAFT agent benzyl dithiobenzoate was demonstrated to be an appropriate chain-transfer agent to inhibit crosslinking and obtain polymers with moderate-to-high conversions. The polymerization of allyl methacrylate led to a polymer without branches but with five- or six-membered rings. However, poly(undecenyl methacrylate) showed an indication of branching rather than intramolecular cycles. The hyperbranched structure of poly(undecenyl methacrylate) was confirmed by a combination of H-1, C-13, H-1-H-1 correlation spectroscopy, and distortionless enhancement by polarization transfer 135 NMR spectra. The branching topology of the polymers was controlled by the variation of the reaction temperature, chain-transfer-agent concentration, and monomer conversion. The significantly lower inherent viscosities of the resulting polymers, compared with those of linear analogues, demonstrated their compact structure,

Organolanthanides with 3-(2-pyridylmethyl) indenyl ligands: synthesis, crystal structures and catalytic activities of divalent complexes for epsilon-caprolactone polymerization

Reaction of 3-(2-pyridylmethyl)indenyl lithium (1) with LnI(2)(THF)(2) (Ln = Sm, Yb) in THF produced the divalent organolanthanides (C5H4NCH2C9H6)(2)Ln(II)(THF) (Ln = Sm (2), Yb (3)) in high yield. 1 reacts with LnCl(3) (Ln = Nd, Sm, Yb) in THF to give bis(3-(2-pyridylmethyl)indenyl) lanthanide chlorides (C5H4NCH2C9H6)(2)Ln(III)Cl (Ln = Nd (4), Sm (5)) and the unexpected divalent lanthanides 3 (Ln = Yb). Complexes 2-5 show more stable in air than the non-functionalized analogues. X-ray structural analyses of 2-4 were performed. 2 and 3 belong to the high symmetrical space group (Cmcm) with the same structures, they are THF-solvated 9-coordinate monomeric in the solid state, while 4 is an unsolvated 9-coordinate monomer with a trans arrangement of both the side-arms and indenyl rings in the solid state. Additionally, 2 and 3 show moderate polymerization activities for F-caprolactone (CL).

A New Method for Preparation and Characterization of Lipo-alkaloid

A simple route for the preparation of lipo-alkaloid is presented. When aconitine or one of its analogues is heated with a fatty acid for 20 min at 100degreesC in water, the C-8 acetyl group of aconitine is displaced by along chain fatty acyl group. The structures of the products were characterized by electrospray ionization tandem mass spectrometry.

The antioxidative effect of icariin in human erythrocytes against free-radical-induced haemolysis

Icariin (2-(4'-methoxyl phenyl)-3-rhamnosido-5-hydroxyl-7-glucosido-8-(3'-methyl-2-butyleny"chromanone) is the major component in Herba Epimedii used in traditional Chinese medicine for the treatment of atherosclerosis. This work focuses on the antioxidative effect of icariin on freeradical-induced haemolysis of human erythrocytes, in which the initial free radical derives from the decomposition of 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) at physiological temperature. To reveal the structure-activity relationship of icariin, the antioxidant effects of two structural analogues of icariin, acacetin (2-(4'-methoxylphenyl)-5,7-dihydroxylchromone) and norwogonin (2-phenyl-5,7,8-trihydroxylchromone), on the same experimental system were examined as well. It was found that all these chromone derivatives (Chm-OHs) dose-dependently protected human erythrocytes against free-radical-induced haemolysis. The order of antioxidative activity was nonvogoni-n > acacetin > icariin by the analysis of the relationship between the concentration of Chm-OHs and the prolongation percentage of the lag time of haemolysis (PP%). It was also proved that the phenyl hydroxyl group attached to the chromone ring at 7-position cannot trap the free radical- On the contrary, phenyl hydroxyl groups at the 5- and 8-position in nonvogonin made it a significant antioxidant in AAPH-induced haemolysis.

16-and 18-electron Cp*Rh complexes with 1,2-dicarba-closo-dodecabofane(12)-1,2-dichalcogenolato ligands, as studied by multinuclear magnetic resonance

The reaction of [Cp*RhCl2](2) 1 with dilithium 1,2-dicarba-closo-dodecaborane(12)-1,2-dithiolate (a) and -diselenolate (b) afforded the 16-electron rhodium(III) half-sandwich complexes Cp*Rh[E2C2(B10H10)] [E=S (3a), Se (3b)]. The 18-electron trimethylphosphane rhodium(III) half-sandwiches Cp*Rh(PMe3)[E2C2(B10H10)] 4a-c were prepared from the reaction of Cp*RhCl2(PMe3) 2 with the same dichalcogenolates, including the ditelluride (c). The complexes 4a,b could also be obtained from the reaction of 3a,b with trimethylphosphane. The molecular geometry of 4b was determined by X-ray structural analysis. The 16-electron complexes 3 an monomeric in solution as shown by multinuclear magnetic resonance (H-1-, B-11-, C-13-, P-31- Se-77-, Rh-103-, Te-125-NMR). also in comparison with the data for the trimethylphosphane analogues 4a-c and for 6a in which the rhodium bears the eta(5)-1,3-C5H3 Bu-t(2) ligand. The Rh-103 nuclear shielding is reduced by 831 ppm (3a) and 1114 ppm (3b) with respect to the 18-electron complexes 4a,b. Similarly, the Se-77 nuclear shielding in 3b is reduced by 676.4 ppm with respect to that in 4b. (C) 1999 Elsevier Science S.A. All rights reserved.

Toxin-screening and identification of bacteria isolated from highly toxic marine gastropod Nassarius semiplicatus

Bacteria isolated from a highly toxic sample of gastropod Nassarius semiplicatus in Lianyungang, Jiangsu Province in July 2007, were studied to probe into the relationship between bacteria and toxicity of nassariid gastropod. The toxicity of the gastropod sample was 2 x 10(2) mouse unit (MU) Per gram Of tissue (wet weight). High concentration of tetrodotoxin (TTX) and its analogues (TTXs) were found in the digestive gland and muscle of the gastropod, using high performance liquid chromatography coupled with mass chromatography (LC-MS). Bacterial strains isolated from the digestive gland were cultured and screened for TTX with a competitive ELISA method. Tetrodotoxin was detected in a proportion of bacterial strains, but the toxin content was low. Partial 16S ribosomal DNA (rDNA) of the TTX-producing strains was then sequenced and compared with those published in the GenBank to tentatively identify the toxic strains. It was found that most of the toxic strains were closely affiliated with genus Vibrio, and the others were related to genus Shewanella, Marinomonas, Tenacibaculum and Aeromonas. These findings suggest that tetrodotoxin-producing bacteria might play an important role in tetrodotoxin accumulation/production in N. semiplicatus. (C) 2008 Elsevier Ltd. All rights reserved.