1-[3-(2-Hydroxyethylsulfanyl)propanoyl]-3,5-bis(benzylidene)-4-piperidones: A novel cluster of P-glycoprotein dependent multidrug resistance modulators.

A series of 1-[3-(2-hydroxyethylsulfanyl)propanoyl]-3,5-bis(benzylidene)-4-piperidones 4a-e display promising P-glycoprotein dependent multidrug resistance (MDR) revertant properties and are significantly more potent than a reference drug verapamil when evaluated against L-5178Y MDR lymphoma cells. These dienones may be referred to as dual agents having both MDR revertant properties and tumour-selective cytotoxicity. In particular, 3,5-bis(4-chlorobenzylidene)-1-[3-(2-hydroxyethylsulfanyl]propanoyl-4-piperidone 4d emerged as a lead molecule for further development based on its MDR revertant properties, cytotoxic potencies and tumour-selective toxicity. The structure-activity relationships reveal important structural requirements for further designing of potent MDR revertants.

Design, synthesis and cytotoxicity of novel chalcone analogs derived from 1-cyclohexylpyrrolidin-2-one and 2,3-dihydrobenzo[f]chromen-1-one.

Two divergent series of novel chalcone analogs, one derived from 1-cyclohexylpyrrolidin-2-one and the other derived from 1-benzo[f]chromanone, were designed, synthesized and evaluated for cytotoxicity against two murine cancer cell lines. Two 1-benzo[f]chromanone analogs, 4g and 4j yielded moderate toxicity against both melanoma B16 and lymphoma L1210 cell lines with IC(50) values between the range of 5 and 6 µM. With an IC(50) value of 3.4 µM, compound 4g was also active against human MDA-MB-435 melanoma cells. X-ray structures of the ß-hydroxy ketone product (4a) and the α,ß-unsaturated ketone (4h) were collected, and confirm the syn-configuration between the carbonyl moiety and the ß-vinylic proton in 4h. X-ray structures of two 1-cyclohexylpyrrolidin-2-one derivatives were also obtained, and both showed an E-configuration for the double bond.

5-Benzyl-idene-3-phenyl-2-phenyl-imino-1,3-thia-zolidin-4-one.

The title compound, C(22)H(16)N(2)OS, is a chalcone analog with a thia-zolidinone core that was synthesized as a potential cytotoxic and anti-cancer agent. The structure is commensurately modulated by unit-cell doubling along the direction of the a axis of the cell. The two crystallographically independent mol-ecules are differerentiated by the dihedral angle between the mean planes of the benzyl-idene phenyl group against the thia-zolidin-4-one moiety, which is 5.01 (7)° in one mol-ecule, and 17.41 (6)° in the other. The two mol-ecules are otherwise close to being indistinguishable and are related by crystallographic pseudo-translation. The two mol-ecules are not planar but are slightly bent with the benzyl-idene and phenyl-imino substituents being bent upwards with respect to the center planes of the two mol-ecules. The degree of bending of the two halves of the thia-zolidin-4-one moieties (defined as the planes that inter-sect at the S atom) are 11.08 (7) and 15.88 (7)°. Packing of the mol-ecules is facilitated by C-H⋯π inter-actions and slipped π-π stacking between one of the phenyl rings and a neighboring ethylene π system [distance between the centroid of the ethylene group and the closest phenyl C atom = 3.267 (2) Å, Cg(phenyl)⋯Cg(ethylene) = 3.926 Å].

A new class of fluorogenic thiazolo[2,3-b]quinazolinone receptor: selective detection towards mercury and hydrogen bisulfate ions in aqueous medium.

A series of fluorophoric and structurally diverse thiazoloquinazoline derivatives were synthesized in a one-pot multicomponent cascade reaction using a microwave irradiation technique. The unique structural arrangement of the synthesized compounds encouraged us to design a new type of bioactive molecular receptor. This receptor interacts with HSO4 - in 1 : 1 and Hg2+ in 1 : 2 binding stoichiometric ratios resulting in a change in fluorescence as well as absorption spectra in aqueous medium. The ion bonded receptor complex possibly enhances the fluorescence signal of the receptor via H-bonded complex formation with HSO4 - ions and co-ordinate complex formation with Hg2+ ions.

Cytotoxic 2-benzylidene-6-(nitrobenzylidene)cyclohexanones which display substantially greater toxicity for neoplasms than non-malignant cells.

Various 2-benzylidene-6-(nitrobenzylidene)cyclohexanones were prepared as candidate cytotoxins in which the nitro group was located in the ortho, meta and para positions leading to series 1-3, respectively. The CC(50) values towards human HSC-2 and HSC-4 oral squamous cell carcinomas as well as human HL-60 promyelocytic leukemic cells are in the low micromolar range in general. On the other hand, most of the compounds afforded clear evidence of being far less toxic towards human HGF gingival fibroblasts, HPC pulp cells and HPLF periodontal ligament fibroblasts which are non-malignant cells. Selectivity index (SI) figures were generated which are the ratios of the average CC(50) values towards normal cells and the CC(50) figure towards a malignant cell line. Huge SI values were obtained for many of the compounds. In particular 1c, 2f, 3c and 3g which have average SI values of >76, >38, 124 and 341, respectively, are clearly lead molecules affording direction for amplification of this area of study. A lead compound 1c caused internucleosomal DNA fragmentation and activation of caspase-3 in HL-60 cells but not in HSC-2 carcinomas. In a short-term toxicity study, doses up to and including 300 mg/kg of the majority of the compounds prepared in this study did not cause any mortalities to mice. Some guidelines for development of these tumor-selective cytotoxins are presented.

1,3-diaryl-2-propenones and 2-benzylidene-1,3-indandiones: a quest for compounds displaying greater toxicity to neoplasms than normal cells.

A series of 1,3-diaryl-2-propenones 2a-j and analogous 2-benzylidene-1,3-indandiones 3a-j were evaluated against various neoplasms and normal cells. In general, greater cytotoxic potencies and selective toxicity to human malignant cells were observed by the compounds in series 2 rather than 3. In particular, 2i emerged as a lead molecule having an average CC(50) figure of 8.6 µM and a selective index value of 18. Various physicochemical features of 2a-j were correlated with the cytotoxic potencies to neoplastic cell lines which provide guidelines for expansion of this series of compounds. The enone 2i induced internucleosomal DNA fragmentation and activated caspase-3 in HL-60 cells suggesting that one of the ways in which the cytotoxicity of the compounds in series 2 is mediated towards some of the cell lines used in this study is by apoptosis. Neurotoxicity in mice was generally lower in series 2 than 3a-j.

The construction of fluorophoric thiazolo-[2,3-b]quinazolinone derivatives: a multicomponent domino synthetic approach.

Acid-mediated one-pot domino reactions of substituted 2-amino thiazoles, substituted benzaldehydes and cyclic diketones have been developed for the synthesis of novel and architecturally unique thiazolo[2,3-b]quinazolinone derivatives under microwave irradiation. In this protocol, a series of thiazolo[2,3-b]quinazolinone derivatives have been synthesized and the excellent fluorescence behaviors of some of the molecules have been reported based on the incorporation of different electron-donating and electron-withdrawing substituents on the aryl moieties of the target molecules.

NC2213: a novel methionine aminopeptidase 2 inhibitor in human colon cancer HT29 cells.

Methionine aminopeptidase 2 (MetAP2) is a bifunctional protein that plays a critical role in the regulation of post-translational processing and protein synthesis. MetAP2 is overexpressed in human colon cancer. In this report we screened various MetAP2 inhibitors and treated HT29 cells with various concentrations of compounds. We evaluated the expression of MetAP2 and pp60c-src expressions in HT29 cells. In addition we also carried out the cell proliferation and cell cycle analysis in the MetAP2 inhibitor-treated HT29 cells. The cell cycle analysis of HT29 treated with 1.0 microM of NC2213 showed an arrest in the G2 phase followed by an induction in the percentage of cells undergoing apoptosis in the sub-G1 phase. Western blot analysis revealed that the MetAP2 expression was dose-dependently decreased when the HT29 cells were treated with the 3,5-bis(benzylidene)-4-piperidone derivative (NC2213). In addition, phosphorylation of Src, a myristoylated oncoprotein was significantly decreased by 1.0 microM of NC2213 as revealed by Western blot analysis. Furthermore, NC2213 also inhibits the expression of pp60c-src in HT29 cells. Interestingly, this compound also inhibits the phosphorylation at Tyr416 of pp60c-src while increasing the phosphorylation at Tyr527 of pp60c-src. NC2213 inhibits the growth of HT29 cells by inducing apoptosis and might be useful for the treatment of human colon cancer.

2-(3-Aryl-2-propenoyl)-3-methylquinoxaline-1,4-dioxides: a novel cluster of tumor-specific cytotoxins which reverse multidrug resistance.

A series of 2-(3-aryl-2-propenoyl)-3-methylquinoxaline-1,4-dioxides 3a-l were prepared by condensation of various aryl aldehydes with 2-acetyl-3-methylquinoxaline-1,4-dioxide 2. These compounds inhibit the growth of human Molt 4/C8 and CEM T-lymphocytes and the IC(50) values are mainly in the 5-30 microM range. The quinoxaline 1,4-dioxide 3j inhibited the growth of 58 human tumor cell lines, particularly leukemic and breast cancer neoplasms. All of the compounds 3a-l reversed the multidrug resistance (MDR) properties of murine L-5178Y leukemic cells which were transfected with the human MDR1 gene. The MDR-reversing effect may be due to the conjugated pi-electron system forming a weak electron charge transfer complex with the P-glycoprotein-mediated efflux pump. The compounds in series 2 and 3 were assessed against HL-60, HSC-2, HSC-3 and HSC-4 malignant cells as well as HGF, HPC and HPLF normal cell lines which revealed that the majority of the compounds displayed a greater toxicity to neoplastic than normal cells. Various ways in which the project may be expanded are presented.

1-Aryl-2-dimethylaminomethyl-2-propen-1-one hydrochlorides and related adducts: A quest for selective cytotoxicity for malignant cells.

The primary objective of this study was to discover one or more clusters of compounds which are not equitoxic but display cytoselectivity toward different malignant cells. Furthermore a most important consideration is that such molecules should also display greater cytotoxic potencies to tumors than normal tissues. Two series of compounds are described which meet these criteria, namely the 1-aryl-2-dimethylaminomethyl-2-propen-1-one hydrochlorides 1a-e and 1-aryl-3-dimethylamino-2-hydroxymethyl-1-propanone hydrochlorides 2a-e. A number of these compounds possess marked cytotoxic potencies (IC(50) and CC(50) values within the 10(-6) and 10(-7) molar range) which are greater than these of the reference drug melphalan. Statistical analyses demonstrated that cytotoxic potencies are influenced by the size of the aryl substituents in series 1 and to some extent by the electronic properties of the aryl groups in series 2. The mode of action of a representative compound 1e in HL-60 cells included inducing apoptosis and activation of caspases -3, -8, and -9.

Cytotoxic 3,5-bis(benzylidene)piperidin-4-ones and N-acyl analogs displaying selective toxicity for malignant cells.

A series of 3,5-bis(benzylidene)piperidin-4-ones 1, 1-acryloyl-3,5-bis(benzylidene)piperidin-4-ones 2 and adducts of 2 with sodium 2-mercaptoethanesulfonate (mesna), namely series 3, were prepared as candidate cytotoxic agents. These compounds were examined against neoplastic HSC-2, HSC-4 and HL-60 cells as well as HGF, HPC and HPLF normal cell lines and many of the compounds displayed selective toxicity for malignant cells. The CC50 values of the analogs in series 2 towards the cancer cell lines were mainly submicromolar. The relative potencies, selectivity and logP values were in the order of 2>1>3. The sulfonic acid group of a representative compound in series 3 was replaced by a thiol function to produce 4 leading to substantial increases in cytotoxic potencies and hydrophobicity indicating that the presence of a hydrophilic sulfonic acid group was disadvantageous in terms of potency. Molecular modeling suggested that the superior cytotoxicity of various members of series 1-3 over an acyclic analog 5 may have been due to the greater torsion angles theta1 and theta2 created between the arylidene aryl rings and the adjacent olefinic groups in series 1-3.

Cytotoxic thiol alkylators.

Various classes of cytotoxic compounds which alkylate cellular thiols are described namely alpha,beta-unsaturated ketones, alpha-methylene-gamma-lactones, azines of Mannich bases, imexon, isothiocyanates, a benzoacronycine as well as activation by thiols prior to alkylation. The mechanisms of action of some of the molecules, such as the formation of reactive oxygen species, are presented. The cytotoxicity of a number of drugs can be influenced by modulation of the concentration of thiols including the observation that potencies can be increased by thiol activation. The ability of certain thiol reagents to reverse multidrug resistance as well as some miscellaneous actions of thiol alkylators are described.

Development of a Scalable Process for the Synthesis of DNDI-VL-2098: A Potential Preclinical Drug Candidate for the Treatment of Visceral Leishmaniasis.

A process suitable for kilogram-scale synthesis of (2R)-2-methyl-6-nitro-2-{[4-(trifluoromethoxy)phenoxy]methyl}-2,3-dihydroimidazo[2,1-b][1,3]oxazole (DNDI-VL-2098, 2), a preclinical drug candidate for the treatment of visceral leishmaniasis, is described. The four-step synthesis of the target compound involves the Sharpless asymmetric epoxidation of 2-methyl-2-propen-1-ol, 8. Identification of a suitable synthetic route using retrosynthetic analysis and development of a scalable process to access several kilograms of 2 are illustrated. The process was simplified by employing in situ synthesis of some intermediates, reducing safety hazards, and eliminating the need for column chromatography. The improved reactions were carried out on the kilogram scale to produce 2 in good yield, high optical purity, and high quality.

Aminothiazoles: Hit to lead development to identify antileishmanial agents.

As part of Drugs for Neglected Diseases initiative's lead optimization program for the development of new chemical entities to treat visceral leishmaniasis (VL), a series of aminothiazoles were synthesized and screened for in vitro efficacy, solubility and microsomal stability. The primary aim of identifying a lead structure with sub-micromolar activity was achieved. Out of 43 compounds synthesized, 16 compounds showed in vitro activity at less than 1 µM against VL. Compound 32 showed excellent antileishmanial potency (IC50 = 3 nM) and had all the acceptable properties except for metabolic instability. Blocking the metabolic soft spots in compound 32, where the 4-methoxy pyridine substituent was replaced by 5-ethoxy group, led to compound 36 (IC50 = 280 nM) with improved stability. To understand the disposition of 36, in vivo pharmacokinetic study was conducted in a mouse model. Compound 36 showed high clearance (91 mL/min/kg); short half-life (0.48 h) after intravenous administration (1 mg/kg) and exposure (AUC0-24) following oral administration was 362 ng h/mL with absolute bioavailability of 8%. To summarize, 43 analogs were synthesized out of which 15 compounds showed very potent sub-nanomolar efficacy in in vitro systems but the liability of metabolic instability seemed to be the major challenge for this chemical class and remains to be addressed.

Unexpected syntheses of seco-cyclopropyltetrahydroquinolines - from a radical 5-exo-trig cyclization reaction: analogs of CC-1065 and the duocarmycins.

Analogs of the seco-cyclopyrroloindoline (seco-CPI), the DNA alkylation pharmacophore of CC-1065 and the duocarmycins, can be prepared through a 5-exo-trig radical cyclization of a free radical and a 3-chloro-2-allylic moiety. This manuscript reports an unexpected discovery that, depending on the structure and stability of the free radical, the cyclization process leads to the production of an appreciable amount of seco- cyclopropyltetrahydroquinolines 7a-d along with the seco-cyclopropoyltetra- hydroindoline products (6a-e). For instance, free radical reaction of the bromoallylic chloride 5a produced an equal amount of 6-benzyloxy-N-t-butoxycarbonyl-3- (chloromethyl)furano[e]indoline (6a), and 7-benzyloxy-N-t-butoxycarbonyl-3-chloro- 1,2,3,4-tetrahydrofurano[f]quinoline (7a). Three other examples that produced mixtures of indoline and quinoline products are provided. In only one of the examples reported in this manuscript, the 6-benzyloxy-N-t-butoxycarbonyl-3-(chloromethyl)benzo[e]indoline, was a seco-CBI precursor 6e formed exclusively, consistent with literature precedents.

3,5-Bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones: a novel cluster of potent tumor-selective cytotoxins.

Novel 3,5-bis(benzylidene)-1-[3-(2-hydroxyethylthio)propanoyl]piperidin-4-ones (3a-e) display potent cytotoxicity and a preferential lethality toward various neoplasms compared to some normal cells. The corresponding sulfonic acid analogues 5a-e and an isostere 4 demonstrated substantially lower activity. The leads 3d and 3e possess very high activity against colon cancer and leukemia cell lines, caused DNA fragmentation, and activated caspase-3 in HL-60 cells. The enones 3b-e were well tolerated in a short-term toxicity screen in mice.

Design, synthesis, and cytotoxicity of novel 3-arylidenones derived from alicyclic ketones.

Forty-four novel chalcone-inspired analogs having a 3-aryl-2-propenoyl moiety derived from alicyclic ketones were designed, synthesized, and investigated for cytotoxicity against murine B16 and L1210 cancer cell lines. The analogs belong to four structurally divergent series, three of which (series g, h, and i) contain differently substituted cyclopentanone units and the fourth (series j) contains a 3,3-dimethyl-4-piperidinone moiety. Of these, the analogs in series j showed potential cytotoxic activity against murine B16 (melanoma) and L1210 (lymphoma) cells. The most active compounds 5j, 11j, 15j, and 12h produced IC(50) values from 4.4 to 15 µm against both cell lines. A single-crystal X-ray structure analysis and molecular modeling studies confirmed that these chalcones have an E-geometry about the alkene bond and possess a slightly 'twisted' conformation similar to that of combretastatin A-4. At a concentration of 30 µm, compounds 5j, 11j, and 15j did not cause microtubule depolymerization in cells, suggesting that they have a different mechanism of action.

The cytotoxic properties and preferential toxicity to tumour cells displayed by some 2,4-bis(benzylidene)-8-methyl-8-azabicyclo[3.2.1] octan-3-ones and 3,5-bis(benzylidene)-1-methyl-4-piperidones.

This study demonstrated that replacement of the axial protons on the C2 and C6 atoms of various 1-methyl-3,5-bis(benzylidene)-4-piperidones 3 by a dimethylene bridge leading to series 2 lowered cytotoxic potencies. Four compounds 2a and 3a-c emerged as lead molecules based on their toxicity towards different neoplasms and their selective toxicity for malignant rather than normal cells. Some possible reasons for the disparity between the IC(50) values in the two series of compounds are presented based on molecular modeling, logP values and respiration in rat liver mitochondria.

Syntheses and cytotoxic properties of the curcumin analogs 2,6-bis(benzylidene)-4-phenylcyclohexanones.

Fifteen curcumin analogs were synthesized and tested for in-vitro cytotoxicity towards B16 and L1210 murine cancer cell lines using an MTT assay. Significant activity was discovered for two analogs: 8 (B16 IC(50) = 1.6 microM; L1210 IC(50) = 0.35 microM) and 9 (B16 IC(50) = 0.51 microM; L1210 IC(50 )= 1.2 microM). Several other analogs exhibited notable cytotoxicity. The data from quantitative structure-activity relationships suggest that large electron-withdrawing substituents placed in the meta-position of the arylidene aryl rings enhance potencies. Compounds 8 and 9 were found using a cell-based assay to have virtually no effects on microtubules at concentrations up to 40 microM. These results suggest that tubulin inhibition is not the principal mechanism by which the curcumin analogs act.

Unusual detritylation of tritylated tetrazole in Sartan molecules.

Tritylated tetrazole of 2a underwent unusual detritylation under basic reaction condition during the synthesis of methyl ether of olmesartan medoxomil 1. The unusual detritylation was found to be a common feature in the case of all tetrazole containing Sartan molecules (3-7).