Parallel synthesis of a desketoraloxifene analogue library via iodocyclization/palladium-catalyzed coupling

For a future structure-activity relationship (SAR) study, a library of desketoraloxifene analogues has been prepared by parallel synthesis using iodocyclization and subsequent palladium-catalyzed coupling reactions. Points of desketoraloxifene diversification involve the two phenolic hydroxyl groups and the aliphatic amine side chain. This approach affords oxygen-bearing 3-iodobenzo[b]thiophenes 4 in excellent yields, which are easily further elaborated using a two-step approach involving Suzuki-Miyaura and Mitsunobu coupling reactions to give multimethoxy-substituted desketoraloxifene analogues 6. Various hydroxyl-substituted desketoraloxifene analogues 7 were subsequently generated by demethylation with BBr(3).     

噁唑烷酮-地拉罗司偶联物的合成及抗菌活性评价（英文）

本文基于“特洛伊木马”策略设计合成了两种具有不同连接臂的噁唑烷酮-地拉罗司偶联物,并进行了抗菌活性评价。与地拉罗司相同,两种偶联物均可与Fe³⁺结合。然而,其对所测试的菌株(包括金黄色葡萄球菌、大肠杆菌、鲍曼不动杆菌和铜绿假单胞菌)均无活性。结果表明,合成的铁螯合剂地拉罗司可能不适合作为细菌转运抗生素的铁离子载体,或者合成的偶联物的连接臂不能在细菌细胞质中水解释放噁唑烷酮,噁唑烷酮-地拉罗司偶联物的设计与合成还需要进一步探索。     

Solid-phase synthesis and biological evaluation of a combinatorial library of philanthotoxin analogues

The modular structure of philanthotoxins was exploited for construction of the first combinatorial library of these compounds using solid-phase parallel synthesis. (S)-Tyrosine and (S)-3-hydroxyphenylalanine were used as amino acid components, spermine, 1,12-dodecanediamine, and 4,9-dioxa-1,12-dodecanediamine as amine components, and butanoyl, phenylacetyl, and cyclohexylacetyl as N-acyl groups. Following automated preparative HPLC, the resulting 18 compounds were isolated as the S-forms in 40-70% yields. The purity of the products was determined by HPLC with evaporative light scattering detection and by (1)H and (13)C NMR. The thus obtained philanthotoxins were tested electrophysiologically for their antagonist properties on human muscle-type nicotinic acetylcholine receptors (nAChR) expressed in TE671 cells and on rat brain non-NMDA glutamate receptors (non-NMDAR) expressed in Xenopus oocytes. 4-Hydroxy analogues lacking the secondary amino groups (PhTX-12 and 4,9-dioxa-PhTX-12 and their analogues) were inactive on non-NMDAR, whereas the potency of the spermine derivatives (PhTX-343 and its analogues) increased with steric bulk of the N-acyl group. The analogue of PhTX-343 in which the N-butanoyl group was replaced by phenylacetyl group had IC(50) of 15 +/- 4 nM on non-NMDAR. Increasing the steric bulk of the N-acyl group was not advantageous for activity at nAChR, and a sharp decrease in potency with increased steric bulk was observed with the derivatives of PhTX-12. 3-Hydroxy analogues generally exhibited lower activity and different response to alterations of the N-acyl groups as compared to the 4-hydroxy analogues. Since the acyl group alterations in PhTX-343 and 4,9-dioxa-PhTX-12 have a similar effect on potency, which is distinctly different from that observed for PhTX-12, the two former compounds may bind to nAChR in a similar fashion but differently from that of PhTX-12. The combinatorial library approach described in this work represents a prototype methodology for future exploration of structure-activity relationships of philanthotoxins.     

Novel cyclopropylindole conjugates and dimers: synthesis and anti-cancer evaluation

There is a considerable interest currently in the development of DNA sequence specific or selective agents for genetic targeting for the control of gene expression, for application in diagnosis or ultimately in therapy. In this context CC-1065 is one of the most impressive lead compounds isolated in trace quantities from the culture of Streptomyces zelensis at Upjohn in 1978. The unique structure was confirmed by single X-ray in 1981. However CC-1065 cannot be used in humans because it was found that it caused delayed deaths in experimental animals. In the search for compounds with better antitumor selectivity and DNA sequence specificity many CC-1065 analogs have been synthesized in an attempt to avoid the undesired side effects while retaining its potency against tumor cells. Two successful attempts in the modification in the active moiety of the parent natural product 1,2,8,8a-tetrahydro-7-methylcyclopropa[3,2-e]indole-4-one (CPI) and 1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indole-4-one (CBI) have been made. We review here recent progress with the analogs of CPI and CBI and their conjugates both by solution and solid phase, also the progress and development of CPI and CBI conjugates with polyamides (information reading molecules in the minor groove of DNA). Since CPI-CPI dimers are significantly more potent than CC-1065 in vitro and in vivo, a large number of CBI-CBI dimers with varying linkers lengths and positions synthesized in our group and their pharmacological properties have been reviewed.     

Thiolated polymers: synthesis and in vitro evaluation of polymer-cysteamine conjugates

The purpose of the present study was to synthesize and characterize novel thiolated polymers. Mediated by a carbodiimide cysteamine was covalently linked to sodium carboxymethylcellulose (CMC) and polycarbophil (PCP). The resulting CMC-cysteamine conjugates displayed 77.9+/-6.7 and 365.1+/-8.7 micromol thiol groups per gram of polymer, whereas the PCP-cysteamine conjugates showed 26.3+/-1.9 and 122.7+/-3.8 micromol thiol groups per gram of polymer (mean+/-S.D.; n=3). In aqueous solutions above pH 5.0 both modified polymers were capable of forming inter- and/or intra-molecular disulfide bonds. The reaction velocity of this oxidation process was accelerated with a decrease in the proton concentration. The oxidation proceeded more rapidly within thiolated CMC than within thiolated PCP. Permeation studies carried out in Ussing-type chambers with freshly excised intestinal mucosa from guinea pigs utilizing sodium fluorescein as model drug for the paracellular uptake revealed an enhancement ratio (R=P(app) (conjugate)/P(app) (control)) of 1.15 and 1.41 (mean+/-S.D.; n=3) for the higher thiolated CMC-cysteamine (0.5%; m/v) and PCP-cysteamine conjugate (1.0%; m/v), respectively. The decrease in the transepithelial electrical resistance values was in good correlation with the enhancement ratios. Due to a high crosslinking tendency by the formation of disulfide bonds stabilizing drug carrier systems based on thiolated polymers and a permeation enhancing effect, CMC- and PCP-cysteamine conjugates represent promising excipients for the development of novel drug delivery systems.     

Antibody-onconase conjugates: cytotoxicity and intracellular routing

Onconase, a member of the pancreatic ribonuclease A superfamily, is currently in Phase III clinical trials for treatment of unresectable malignant mesothelioma. The anticancer effect of onconase may relate to its intracellular target, a non-coding RNA. Some non-coding RNAs are aberrantly expressed in cancer cells. This discovery is creating new interest in drugs that target RNA. Conjugating onconase to agents that recognize tumor associated molecules further increases its potency and specificity. Analysis of onconase activity when directed to two different internalizing and one non-internalizing receptor reveals that the ideal targeting agents would rapidly enter lysosomal compartments before onconase escaped to the cytosol. Antibody-onconase conjugates are effective in preclinical models, cause little non-specific toxicities in mice and have favorable formulation properties. Understanding the reason for their potency coupled with understanding novel RNA-based mechanisms of tumor cell death will lead to improved variations of targeted onconase.     

Ketorolac-dextran conjugates: synthesis, in vitro and in vivo evaluation

Ketorolac is a non-steroidal anti-inflammatory drug. Dextran conjugates of ketorolac (KD) were synthesized and characterized to improve ketorolac aqueous solubility and reduce gastrointestinal side effects. An N-acylimidazole derivative of ketorolac (KAI) was condensed with a model carrier polymer, dextran of different molecular masses (40000, 60000, 110000 and 200000). IR spectral data confirmed formation of ester bonding. Ketorolac contents were evaluated by UV-spectrophotometric analysis. The molecular mass was determined by measuring viscosity using the Mark-Howink-Sakurada equation. In vitro hydrolysis studies were performed in aqueous buffers (pH 1.2, 7.4, 9) and in 80% (V/V) human plasma (pH 7.4). At pH 9, a higher rate of ketorolac release from KD was observed as compared to aqueous buffer of pH 7.4 and 80% human plasma (pH 7.4), following first-order kinetics. In vivo biological screening in mice and rats indicated that conjugates retained analgesic and anti-inflammatory activities with significantly reduced ulcerogenicity compared to the parent drug.     

Design,synthesis and evaluation of alkylphosphocholine-gefitinib conjugates as multitarget anticancer agents

The evolving resistance to the currently used chemotherapeutic agents requires continuous efforts to develop new anticancer agents overcoming resistance and with lower side effects. Polypharmacology via designing a single molecule intercepting multiple signaling pathways is more effective than targeting a single one. Several alkylphosphocholines show anticancer activity via inhibition of Akt phosphorylation. On the other hand, several molecules having quinazoline scaffold elicit anticancer activity through inhibition of epidermal growth factor receptor (EGFR) tyrosine kinases. We report our efforts to develop alkylphosphocholines-gefitinib conjugates as multitarget anticancer agents. The antiproliferative activities of the newly synthesized compounds were evaluated against cell lines representing lung, breast, liver and skin cancers. In addition, the capability of the newly synthesized compounds to inhibit Akt phosphorylation and EGFR tyrosine kinases were determined. The results emphasized the influence of the linkers’ length on the elicited bioactivity. The long chain linkers possessing conjugates were more active regarding both of the elicited antiproliferative effect and inhibition of Akt phosphorylation, while maintained the ability to inhibit EGFR tyrosine kinases. Their cytotoxic activities were superior or comparable to erlotinib and miltefosine.     

Design,synthesis and evaluation of the cytotoxicity of a N-mustard and paclitaxel conjugate prodrug

The syntheses and preliminary biological evaluation of a potentially bioreductive N-mustard and paclitaxel conjugate prodrug 3 targeting hypoxic tumor tissue are described. Aromatic nitro group was used as the bio-reductive trigger. Generation of paclitaxel occurred after reduction via a subsequent mechanism of “cyclization-cyclization-extrusion”. The prodrug was stable in PBS (pH = 7.4) and released paclitaxel after chemical reduction of the nitro functionality. In aerobic cytotoxicity assays, it exhibited diminished cytotoxicity and is a candidate for further biological evaluation.     

Design,synthesis and evaluation of genistein-polyamine conjugates as multi-functional anti-Alzheimer agents

A series of genistein-polyamine conjugates (4a–4h) were designed, synthesized and evaluated as multi-functional anti-Alzheimer agents. The results showed that these compounds had significant cholinesterases (ChEs) inhibitory activity. Compound 4b exhibited the strongest inhibition to acetylcholinesterase (AChE) with an IC₅₀ value of 2.75 μmol/L, which was better than that of rivastigmine (5.60 μmol/L). Lineweaver–Burk plot and molecular modeling study showed that compound 4b targeted both the catalytic active site (CAS) and the peripheral anionic site (PAS) of AChE. Besides, compound 4b showed potent metal-chelating ability. In addition, it was found that 4a–4h did not affect HepG-2 cell viability at the concentration of 10 μmol/L.KEY WORDS: Genistein, Polyamine, Alzheimer׳s disease, Acetylcholinesterase, Molecular modeling, Metal-chelating, Inhibition, Rivastigmine     

Vitamin C and 6-amino-vitamin C conjugates of diclofenac: synthesis and evaluation

Diclofenac (Diclo), its ascorbic acid (AA) or 6-amino-AA (AA-NH2) pro-drugs (AA-Diclo or AA-NH-Diclo) were prepared and evaluated on human retinal pigment epithelium (HRPE) cells to investigate their ability to interact with the vitamin C transporter SVCT2 and their cellular uptake. Furthermore, stabilities in physiological fluids of these compounds were investigated. For kinetic experiments, AA-Diclo was incubated in Tris-HCl buffer, human plasma or whole blood. The extracted samples were analysed by HPLC. AA-Diclo was hydrolysed following first order kinetics in buffer, plasma (t1/2 about 10 h) and whole blood (t1/2 about 3.5 h). Transport and inhibition assays were performed by adding [14C]AA and the above-mentioned unlabelled compounds to plated HRPE cells. Intracellular accumulation was measured incubating HRPE cells with increasing concentrations of unlabelled compounds, following by HPLC analysis. Diclo resulted as a non-competitive inhibitor of AA-transport, showing a Na+-dependent and ascorbate-independent uptake. AA-Diclo behaved as a competitive inhibitor, but it was not transported into cells, whereas its analogue AA-NH-Diclo showed a decreased inhibitory activity. Stability studies suggest AA-Diclo as a potential candidate to enhance the Diclo short half life in vivo. The discovery of a Na+-dependent transporter for Diclo on HRPE cells opens new perspectives for targeting diclofenac into the brain.     

Aminoacyl-anthraquinone conjugates as telomerase inhibitors: synthesis, biophysical and biological evaluation

The telomerase-telomere complex is a prospective anticancer target. To inhibit enzyme activity by induction of G-quadruplex in human telomeres, we have synthesized a small library of 2,6- and 2,7-amino-acyl/ peptidyl anthraquinones with diverse connecting linkers, charge, lipophilicity and bulk. The test compounds modulated G-quadruplex stability to different extents and showed clear preference for quadruplex over duplex DNA. Telomerase inhibition correlated with G-quadruplex stabilization. A SAR analysis showed that type of linkage between the linker and the anthraquinone, together with the position of the side chains and the nature of the amino acid components play a major role both in stabilizing G-quadruplex and producing telomerase inhibition. Short-term cytotoxic activity was poor. However, after prolonged exposure to effective G-quadruplex binders, cells became senescent. These results are of help in the rational design of more efficient G-quadruplex stabilizers, possibly endowed with cancer cell-selective antiproliferative effects.     

Total synthesis and cytotoxicity evaluation of syrinenin-4-O-farnesylether and its analogues

First synthesis of natural product, syrinenin-4-O-farnesylether (1), was carried out via two different paths. Four of its derivatives (9–12) were also prepared. Cytotoxicity screening of the selected compounds were performed on six tumour cell lines. Compound 12 exhibited prominent IC₅₀ values of 1.9 μM and 0.8 μM on CNE and PC-3 cells, respectively.     

Total synthesis and cytotoxicity evaluation of syrinenin-4-O-farnesylether and its analogues

First synthesis of natural product, syrinenin-4-O-farnesylether (1), was carried out via two different paths. Four of its derivatives (9-12) were also prepared. Cytotoxicity screening of the selected compounds were performed on six tumour cell lines. Compound 12 exhibited prominent IC50 values of 1.9 microM and 0.8 microM on CNE and PC-3 cells, respectively.     

Thiolated polymers--thiomers: synthesis and in vitro evaluation of chitosan-2-iminothiolane conjugates

The aim of this study was to improve the properties of chitosan as excipient in drug delivery systems by the covalent attachment of thiol moieties. This was achieved by the modification of chitosan with 2-iminothiolane. The resulting chitosan–4-thio-butyl-amidine conjugates (chitosan–TBA conjugates) displayed up to 408.9±49.8 μmol thiol groups per gram polymer. Because of the formation of disulfide bonds based on an oxidation process of the immobilized thiol groups under physiological conditions, chitosan–TBA conjugates exhibit in situ gelling properties. After less than 2 h, 1.5% (m/v) chitosan–TBA conjugate solutions of pH 5.5 formed covalently cross-linked gels. The viscosity increased in positive correlation with the amount of thiol groups immobilized on chitosan. In addition, also the mucoadhesive properties were strongly improved by the covalent attachment of thiol groups on chitosan. The adhesion time of tablets based on the unmodified polymer on freshly excised porcine intestinal mucosa spanned on a rotating cylinder in an artificial intestinal fluid was extended more than 140-fold by using the thiolated version. Drug release studies out of tablets comprising the chitosan–TBA conjugate demonstrated that an almost zero-order release kinetic was achieved for the model drug clotrimazole within the first 6 h. The modification of chitosan with 2-iminothiolane leads, therefore to thiolated polymers, which represent a promising tool for the development of in situ gelling and/or mucoadhesive drug delivery systems.     

A facile synthesis and anticancer activity evaluation of spiro[thiazolidinone-isatin] conjugates

The synthesis and evaluation of the anticancer activity of 3'-aryl-5'-arylidene-spiro[3H-indole-3,2'-thiazolidine]-2,4'(1H)-diones and spiro[3H-indole-3,2'-thi-azolidine]-2,4'(1H)-dione-3'-alkanoic acid esters were described. The structure of the compounds was determined by (1)H and (13)C NMR and their in vitro anticancer activity was tested in the National Cancer Institute. Among the tested compounds, (5'Z)-5'-(benzylidene)-3'-(4-chlorophenyl)spiro[3H-indole-3,2'-thia-zolidine]-2,4'(1H)-dione (IIa) and (5'Z)-3'-(4-chlorophenyl)-5'-[4-(1-methylethyl)-benzylidene]spiro[3H-indole-3,2'-thiazolidine]-2,4'(1H)-dione (IIb) were superior to other related compounds.     

Statistical molecular design, parallel synthesis, and biological evaluation of a library of thrombin inhibitors

A library of thrombin inhibitors has been designed using statistical molecular design. An aromatic scaffold was used, with three varied positions corresponding to three pockets at the active site of thrombin (the S-, P-, and D-pockets). The selection was performed in the building block space, and previously acquired data were included in the design procedure. The design resulted in six, four, and six building blocks for the first (S), second (P), and third (D) pockets, respectively. A second round of selection applied to the combined selected building blocks resulted in a subset of 18 compounds. The selected library was synthesized in parallel and biologically evaluated. The compounds were analyzed with respect to their inhibition (pIC(50)) of thrombin; membrane permeability, estimated by migration behavior in micellar media (CE log k') and pK(a); and specificity with respect to inhibition (K(i)) of trypsin. Multivariate QSAR studies of the responses yielded valuable results and information that could only be found using statistical molecular design in combination with multivariate analysis.