Structural Modifications of cis‐Glycofused Benzopyran Compounds and Their Influence on the Binding to Amyloid‐β Peptide

A small library of glycofused tricyclic compounds with a central pyran ring chemically modified in the position para to the ring oxygen has been synthesised. The influence of the chemical modification on the structural conformation of the compounds and on their ability to bind Aβ peptide has been evaluated respectively using molecular mechanics (MM) and molecular dynamics (MD) simulations, and STD NMR spectroscopy. The introduction of particularly polar/charged groups leads to the loss of binding ability, without a significant change in the conformation, whilst other substitutions does not significantly affect either the structural conformation or the binding.     

Chemical modification and anticancer effect of prenylated flavanones from Taiwanese propolis

Our previous studies demonstrated that eight prenylated flavanones (1-8), isolated from Taiwanese propolis, were capable of a broad spectrum of biological activities. Among them, nymphaeol A (3), nymphaeol B (4) and nymphaeol C (7), abundant in Taiwanese propolis, exhibited cytotoxicity against cancer cell lines. It therefore seemed interesting to improve their activity via a semi-synthetic strategy. In this study, 12 novel prenylated flavanones were synthesised in our laboratory and their activities were assessed for two human prostate cancer cell lines, PC-3 and DU-145, and a human hepatoma cell line, Hep-3B. Of these compounds, 10c, 11 and 12 showed more potent cytotoxicity against the PC-3 cell line than 5-Fu. Using cytometric analysis followed by double staining with annexin V-FITC and propidium iodide, it was observed that these compounds induced apoptosis as well. This suggests that prenylated flavanones 10c, 11 and 12 may have anticancer potential for further development.     

Taumycins A and B, two bioactive lipodepsipeptides from the Madagascar sponge Fascaplysinopsis sp

Two closely related lipodepsipeptides, taumycins A and B (1 and 2) have been isolated from the Madagascar sponge Fascaplysinopsis sp. The two compounds have the same 12-membered oxodepsipeptide ring system in common. Both were toxic to brine shrimp larvae, and taumycin A (1 microM), but not taumycin B, inhibited growth of the human UT-7 leukemic cell line. The structure of the two compounds, likely to be derived from microorganisms, was established by MS and 1D and 2D NMR data.     

N9位芳基取代嘌呤-8-酮类衍生物的合成及抗肿瘤活性

合成了一系列N9位芳基取代嘌呤-8-酮类衍生物, 利用核磁共振氢谱(¹H NMR)、 核磁共振碳谱(¹³C NMR)和高分辨质谱(HRMS)进行了结构确证. 采用四甲基偶氮唑盐(MTT)法测定了目标化合物的体外抗肿瘤细胞增殖活性. 结果表明, 嘌呤酮环的C2位及N9位的取代对活性有较大影响, C2位引入对位由含氮六元环取代的苯胺, N9位引入对三氟甲基苯均有利于提高抗肿瘤活性. 化合物12c对人白血病细胞(K562)、 人前列腺癌细胞(PC-3)、 人乳腺癌细胞(MDA-MB-231)及人结肠癌细胞(HCT116)的抑制效果明显优于阳性对照药R-Roscovitine.     

Oxidative rearrangements of tricyclic vinylcyclobutane derivatives

Three tricyclic vinylcyclobutanes (3-methylenetricyclo[5.3.0.0(2,6)]decanes 1-3) have been subjected to ionization by photoinduced electron transfer in solution and by X-irradiation in Ar matrices. All three compounds undergo oxidative cycloreversion; the cleavage of the four-membered ring, however, occurs in a different direction depending on the presence of a methyl group in position 6 of the tricyclic framework. In those derivatives, cycloreversion is found to lead to 1-methyl-8-methylene-1,6-cyclodecadiene radical cations (5.+ from 1, 8.+) from 2) which upon back electron transfer yield two different hydrocarbons (6 from 5.+, 9 from 8.+), depending on the configuration around the endocyclic double bonds of the respective cyclodecadiene derivative. In the absence of a methyl group on C6, the cycloreversion leads to a radical cation complex between 1-methylenecyclopent-2-ene and cyclopentene (12.+) which appears to revert to 3 on back electron transfer. The intermediate radical cations 5.+, 8.+, and 12.+ have been identified and characterized by UV/Vis and IR spectra in Ar matrices. The mechanism of their formation is elucidated by quantum chemical calculations.     

Triazolylbenzimidazolthiones and derivatives of the new 1,2,3‐triazolo[ 1,5‐a][ 1,3,5]benzotriazepine heterocycle

Four new triazolylbenzimidazolthione derivatives (2a‐d), analogous to triazolylbenzimidazolone derivatives previously tested as activators of the BK_Ca potassium channels, were prepared and assayed without success. Some derivatives of a new tricyclic nitrogen heterocycle, 1,2,3‐triazolo[1,5‐a][1,3,5]benzo‐triazepine, bearing a carboxamido group in the 3 position, other substituents in the 8 position and a carbonyl (5a‐d) or thione (6a‐c) or methylthio (7a‐c) function in the 5 position were synthesised. The nucleophilic displacement of the methylthio substituent with morpholine or cyclopentylamine provided the 5‐amino‐substituted tricyclic derivatives 8a‐d. Starting from the l‐(2‐nitrophenyl)‐4‐cyano‐5‐amino‐1,2,3‐triazole (9), the 3‐cyano‐triazolobenzotriazepin‐5‐one derivative 12 was also obtained. The majority of the new compounds were tested towards the BK_Ca potassium channels, the benzodiazepine and adenosine A₁ and A_2a receptors, but no remarkable activity was detected.     

Conformationally restricted goniofufurone mimics with halogen,azido or benzoyloxy groups at the C-7 position: Design,synthesis and antiproliferative activity

A series of new conformationally restricted goniofufurone mimics, bearing an additional 1,3-dioxan ring and a halogen, azido or benzoyloxy functionality at the C-7 position has been designed and synthesized. The Appel reaction was used for replacement of 7-OH group with Cl or Br functions in tricyclic lactone (3). 7-Iodo derivative (3d) was prepared by using the Ph₃P/I₂/2,6-lutidine reagent system. 7-Fluoro group was introduced by treatment of 3 with DAST, while the corresponding 7-azido and 7-benzoyloxy derivatives have been prepared by multistep sequences. Synthesized products were evaluated for their ability to inhibit growth of selected human malignant cell lines. Structure-activity relationships demonstrated that the nature of a substituent at the C-7 position could enhance the antiproliferative activity of the analogues. The preliminary study on the mechanisms indicated that all synthesized compounds induced apoptosis in 61–77% of K562?cells.     

Synthesis of bridged carbocyclic systems related to diterpenes involving intramolecular cyclisation of diazomethyl ketones

The tricyclic dienediones 5,6 and 7 have been synthesised for entry into the ring systems of the tetracyclic diterpenes atisirene (1), phyllocladene (3) and hibaene (4) respectively.     

Synthesis,Crystal Structure and Antimicrobial Property of Dehydroabietylamine Acetate

Two compounds of dehydroabietylamine acetate 1 and dehydroabietylamine 2 have been studied. The X-ray study demonstrated that compound 1 is in orthorhombic space group P212121 with a = 6.1310（12）, b = 10.605（2）, c = 35.717（7）A, C23H39NO3, Mr = 377.55, V = 2322.3（8）A^3, Z = 4, Dc = 1.080 g/cm^3, F（000） = 832,μ = 0.070 mm^-1, R = 0.0795 and wR = 0.1528. Hydrogen bonds are cross-linked by the N and O atoms to form one-dimensional chains running along the a axis. Antibacterial analysis shows strong activity against studied bacteria and fungi in compound 2.     

Machilusides A and B: structurally unprecedented homocucurbitane glycosides from the stem bark of Machilus yaoshansis

Two structurally novel homocucurbitane triterpenoid glycosides, machilusides A (1) and B (2), possessing an unprecedented C(36) skeleton with a D-fructose moiety incorporated into a cucurbitane nucleus forming unique cage-like tricyclic ring moieties, were isolated from the stem bark of Machilus yaoshansis. Their structures were determined by spectroscopic methods. Both compounds exhibited nonselective cytotoxic activities against several human cancer cell lines. The biosynthetic pathway of 1 and 2 was postulated.     

Synthesis of tricyclic pyrazolopyrimidine arylidene ester derivatives and their cytotoxic and molecular docking evaluations

Our research team has synthesized 33 tricyclic pyrazolopyrimidine arylidene ester derivatives using the lead compound CAM551 as a starting point. This was achieved by a designed five-step synthesis strategy. The synthesized compounds' inhibitory activities against HT-116 human colorectal adenocarcinoma cell line and HGC27 human gastric cancer cells were assessed through traditional MTT assays. The designed and synthesized compounds demonstrated superior inhibition against both types of cancer cells. Additionally, compound 7b , which contains a long-chain substituent, exhibited improved inhibition against hepatocellular carcinoma cells and a greater safety profile. These findings indicate that compound 7b has the potential as an antitumor lead compound for future research.     

槲皮素-3-O-丙基衍生物的合成及生物活性研究

槲皮素是具有丰富生物活性的黄酮类化合物,药理活性显著。本文以槲皮素为先导物,选择性对C环3位羟基进行修饰,以廉价的芦丁为原料,经苄基保护、Williamson成醚反应,再经Pd/C催化加氢脱苄基得到28个未见文献报道的槲皮素-3-O-丙基衍生物,其结构经¹H NMR、¹³C NMR、ESI-MS进行确证。采用MTT法考察了所合成化合物对人食管鳞癌（EC109）、人胃癌（HGC27）、人乳腺癌（MCF-7）、小鼠黑色素瘤（B16-F10）的增殖抑制作用。结果显示,通过化学方法对槲皮素结构进行修饰后,其体外抗肿瘤活性增强。其中,化合物F3(IC₅₀=5.23±0.37μmol/L)、F5(IC₅₀=2.63±0.09μmol/L)对小鼠黑色素瘤（B16-F10）抑制作用比5-氟尿嘧啶(IC₅₀=14.38±0.27μmol/L)好,值得进一步研究。     

Synthesis and studies of calcium channel blocking and antioxidant activities of novel 4-pyridinium and/or N-propargyl substituted 1,4-dihydropyridine derivatives

The novel 1,4-dihydropyridine derivatives containing the cationic pyridine moiety at the position 4, and the N-propargyl group as a substituent at position 1 of the 1,4-DHP cycle were designed, synthesised, and assessed in biological tests. Among all the novel compounds, the 4-(N-dodecyl) pyridinium group-containing compounds 11 (without the N-propargyl group) and 12 (with the N-propargyl group) demonstrated the highest calcium antagonistic properties against neuroblastoma SH-SY5Y (IC₅₀ about 5–14 μM) and the vascular smooth muscle A7r5 cell (IC₅₀ – 0.6–0.7 μM) lines, indicating that they predominantly target the L-type calcium channels. These compounds showed a slight total antioxidant activity. At concentrations close to those of L-type calcium channel blocking ones, compound 12 did not affect mitochondrial functioning; also, no toxicity was obtained in vivo. The N-propargyl group as a substituent at position 1 of the 1,4-DHP cycle did not essentially influence the compounds’ activity. The 4-(N-dodecyl) pyridinium moiety-containing compounds can be considered as prototype molecules for further chemical modifications and studies as cardioprotective/neuroprotective agents.     

Dioxadispiroketal Compounds and a Potential Acyclic Precursor from Amomum aculeatum

Four new compounds having an unusual 1,7-dioxadispiro[5.1.5.2]-12-ene-11-one tricyclic ring system (1-4), their potential precursor, 5R-hydroxy-1-(4-hydroxyphenyl)-eicosan-3-one (5), and two known compounds, aculeatins A (6) and B (7), have been isolated from Amomum aculeatum. All compounds were characterized by spectroscopic methods and the configurations were established by 2D NOE correlations. Compounds 1-4, 6, and 7 showed cytotoxic activity against several human cancer cell lines.     

Proton magnetic resonance studies of compounds with bridgehead nitrogen atoms—XXIII: Deformation of the piperidine ring in some bicyclic compounds possessing a bridgehead amide nitrogen atom

Some bridgehead nitrogen compounds possessing the CH(Me)-bridgehead N? C(O) system have been synthesised and their configurations assigned. The chemical shifts of the proton geminal to the methyl group provides evidence for the existence of a deformed chair conformation for the methyl substituted ring.     

Cytotoxic activity of antioxidant constituents from Hypericum triquetrifolium Turra

The Sulforodamine B (SRB) assay was used to test cytotoxicity against four human cancer cell lines and one normal cell line of antioxidant constituents isolated from Hypericum triquetrifolium Turra. Methanolic extract and pure compounds were tested against the large cell lung carcinoma cell line COR-L23, the hepatocellular carcinoma cell line HepG-2, renal cell adenocarcinoma ACHN, the amelanotic melanoma cell line C32 and normal human foetal lung MRC5. The results showed that I3-II8-biapigenin exhibited strong cytotoxic activity (IC50 = 5.73 micro g mL(-1)) showing a certain degree of selectivity against the different cell types.     

支链/环链烷氧基乙酸为离去配体的铂(Ⅱ)配合物的体外活性研究

合成了12个带支链/环链烷氧基乙酸为离去基团的顺铂类配合物,通过元素分析、红外光谱、核磁共振氢谱和质谱对配合物进行了表征。研究了所有化合物对人非小细胞肺癌A549、人肝癌细胞BEL-7402和人乳腺癌细胞MCF-7细胞系的体外抗肿瘤活性。测试结果表明,12个配合物中有5个对人乳腺癌细胞系MCF-7有较好的体外活性。其中化合物2(顺-二(异丙氧基乙酸根)·二氨合铂(Ⅱ))在所有的化合物中显示最高的活性,对所测3个细胞系都是如此。     

Total synthesis of the marine sponge metabolites (+)-rottnestol, (+)-raspailol A and (+)-raspailol B

The asymmetric syntheses of (+)-rottnestol (1) and the related marine sponge metabolites (+)-raspailols A (5) and B (6) are described. The key step in each of these sequences was a Stille coupling to form the C9-C10 sp2-sp2 bond and connect the polyene sidechains to the appropriate optically active tetrahydropyran core. For rottnestol (1), both C12 epimers were synthesised by a coupling between stannane 7 and (R)- or (S)-8 followed by acid hydrolysis which allowed for the assignment of the absolute configuration at the remote C12 stereocentre as R upon comparison of chiroptical data of the synthetic material with that reported for the natural product. In accord with this, (12R)-raspailol A (5) was synthesised from stannane 7 and sidechain 9 and this compound also compared well with the data for natural material including sign and absolute value of the specific rotation. Finally, the same C12 epimer of raspailol B (6) was secured via a union between stannane 10 and iodide 9 and this also possessed a similar rotation to that described for the natural product. Thus, all three compounds appear to possess the (12R) configuration, while that of the core tetrahydropyran ring is the same as proposed originally.     

Novel achiral indole-substituted titanocenes: Synthesis and preliminary cytotoxicity studies

A series of eight new titanocene dichloride derivatives has been synthesised and characterized. Four compounds from the series are lypophilic indole-functionalised titanocenes and four are hydrochloride salts of their dimethylaminomethyl-functionalised counterparts, which are water soluble. The compounds were tested for their in vitro cytotoxicities against the human kidney cancer cell line CAKI-1 and their results are compared with previously synthesised structural analogues. Surprisingly, two of the compounds showed no activity against the CAKI-1 cell line; however six compounds exhibited medium to high potency with IC50 values as low as 7.0 μM. These six complexes were tested further on this cell line using the co-solvent Soluphor P, which has been shown to improve both solubility and cytotoxicity of similar complexes. One of the compounds carrying a N-methylindole-substituent was obtained in the form of single crystals and allowed for the characterisation by X-ray crystallography; the compound crystallised in the space group P2₁/n (#14) with four molecules present in the monoclinic unit cell.     

Synthesis and immunosuppressive activity of L-rhamnopyranosyl flavonoids

Astilbin, a flavonoid isolated from different plants, shows diverse biological activities. This paper reports the synthesis and immunosuppressive activity of seven analogues of astilbin, which may shed light on the structure-activity relationship of the compounds. The following glycosyl flavonoids, 6-alpha-L-rhamnopyranosyloxyflavanone (20), 3-alpha-L-rhamnopyranosyloxyflavone (22), 3-alpha-L-rhamnopyranosyloxyflavanone (24), 3-alpha-L-rhamnopyranosyloxychromanone (26), 4-alpha-L-rhamnopyranosyloxychromanol (27), 7-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (30) and 4'-hydroxy-3-alpha-L-rhamnopyranosyloxyflavanone (32) were prepared respectively by glycosylation of 6-hydroxyflavanone (1), 3-hydroxyflavone (2), 3-hydroxyflavanone (5), 3-hydroxychromanone (8), 4-chromanol (9), 7-benzyloxy-3-hydroxyflavanone (12), 4'-benzyloxy-3-hydroxyflavanone (15). Among them, compounds 5, 8, 12 and 15 were synthesized from flavanone (3), 4-chromanone (6), 7-hydroxyflavanone (10) and 4'-hydroxyflavanone (13) respectively. Similar to astilbin (4), compounds 22, 24, 26, 30 and 32 significantly inhibited the single mixed lymphocytes reaction (sMLR) and enhanced the apoptosis of spleen cells isolated from mice with sheep red blood cell-induced delayed-type hypersensitivity respectively. However, compound 20 only showed a slight tendency to inhibit sMLR at higher concentration. Both compounds 20 and 27 did not influence the cell apoptosis. These data suggest that the following factors play essential roles in determining the biological activity of the flavonoids: the position at which the sugar is linked to the flavone, the presence of carbonyl on C-4 and phenol hydroxyl group in A or B ring. However, the presence of a B ring is unfavorable for the biological activity and the double bond at C2-C3 in C-ring shows little effect on the activity.