2,6-disubstituted pyran-4-one and thiopyran-4-one inhibitors of DNA-Dependent protein kinase (DNA-PK)

6-aryl-2-morpholin-4-yl-4H-pyran-4-ones and 6-aryl-2-morpholin-4-yl-4H-thiopyran-4-ones were synthesised and evaluated as potential inhibitors of the DNA repair enzyme DNA-dependent protein kinase (DNA-PK). Several compounds in each series exhibited superior activity to the chromenone LY294002, and were of comparable potency to the benzochromenone NU7026 (IC(50)=0.23 microM). Importantly, members of both structural classes were found to be selective inhibitors of DNA-PK over related phosphatidylinositol 3-kinase-related kinase (PIKK) family members. A multiple-parallel synthesis approach, employing Suzuki cross-coupling methodology, was utilised to prepare libraries of thiopyran-4-ones with a range of aromatic groups at the 3'- and 4'-positions on the thiopyran-4-one 6-aryl ring. Screening of the libraries resulted in the identification of 6-aryl-2-morpholin-4-yl-4H-thiopyran-4-ones bearing naphthyl or benzo[b]thienyl substituents at the 4'-position, as potent DNA-PK inhibitors with IC(50) values in the 0.2-0.4 microM range.     

Aminostyrylbenzofuran derivatives as potent inhibitors for Abeta fibril formation

The synthesis of a novel series of aminostyrylbenzofuran derivatives 1a-w and their inhibitory activities for Abeta fibril formation were described. All the synthesized compounds were evaluated by thioflavin T (ThT) assay and displayed potent inhibitory activities for Abeta fibril formation. Among them, compounds 1i and 1q exhibited excellent inhibitory activities (IC(50)=0.07 and 0.08 microM, respectively) than those of Curcumin (IC(50)=0.80 microM) and IMSB (IC(50)=8.00 microM) as reference compounds. Both compounds were selected as promising candidates for further biological evaluation.     

Synthesis and exploration of novel curcumin analogues as anti-malarial agents

Curcumin, a major yellow pigment and active component of turmeric, has been shown to possess anti-inflammatory and anti-cancer activities. Recent studies have indicated that curcumin inhibits chloroquine-sensitive (CQ-S) and chloroquine-resistant (CQ-R) Plasmodium falciparum growth in culture with an IC(50) of approximately 3.25 microM (MIC=13.2 microM) and IC(50) 4.21 microM (MIC=14.4 microM), respectively. In order to expand their potential as anti-malarials a series of novel curcumin derivatives were synthesized and evaluated for their ability to inhibit P. falciparum growth in culture. Several curcumin analogues examined show more effective inhibition of P. falciparum growth than curcumin. The most potent curcumin compounds 3, 6, and 11 were inhibitory for CQ-S P. falciparum at IC(50) of 0.48, 0.87, 0.92 microM and CQ-R P. falciparum at IC(50) of 0.45 microM, 0.89, 0.75 microM, respectively. Pyrazole analogue of curcumin (3) exhibited sevenfold higher anti-malarial potency against CQ-S and ninefold higher anti-malarial potency against CQ-R. Curcumin analogues described here represent a novel class of highly selective P. falciparum inhibitors and promising candidates for the design of novel anti-malarial agents.     

Pentacyclic triterpenes. Part 5: synthesis and SAR study of corosolic acid derivatives as inhibitors of glycogen phosphorylases

The synthesis and biological evaluation of corosolic acid derivatives and related compounds as inhibitors of rabbit muscle glycogen phosphorylase a is described. Within this series of compounds, 8 (IC(50)=7.31 microM), 12d (IC(50)=3.26 microM), and 12e (IC(50)=5.1 microM) exhibited more potent activities than the parent compound 1 (IC(50)=20 microM). SAR of these compounds is also discussed.     

Indole derivatives as potent inhibitors of 5-lipoxygenase: design, synthesis, biological evaluation, and molecular modeling

A series of novel indole derivatives was designed, synthesized and evaluated by cell-based assays for their inhibitory activities against 5-LOX in rat peritoneal leukocytes. Most of them (30 out of 35) showed an inhibitory potency higher than the initial screening hit 1a (IC(50)=74 microM). Selected compounds for concentration-response studies showed prominent inhibitory activities with IC(50) values ranging from 0.74 microM to 3.17 microM. Four compounds (1m, 1s, 4a, and 6a) exhibited the most potent inhibitory activity compared to that of the reference drug (Zileuton), with IC(50) values less than 1 microM. Molecular modeling studies for compounds 1a, 3a, 4a, and 6a were also presented. The excellent in vitro activities of this class of compounds may possess potential for the treatment of LT-related diseases.     

Structure-activity relationship of aza-steroids as PI-PLC inhibitors

A number of aza-steroids were synthesized as potent phosphatidylinositol phospholipase C (PI-PLC) inhibitors. The epimeric mixtures 22,25-diazacholesterol (8a) and 3beta-hydroxy-22,25-diazacholestane (8b) were among the most active of these inhibitors, with IC(50) values of 7.4 and 7.5 microM, respectively. The 20alpha epimer, 8a2 (IC(50)=0.64 microM), whose stereochemistry at C-20 coincides with that of cholesterol, was found 50 times more potent than the 20beta epimer, 8a1 (IC(50)=32.2 microM). In diaza-estrone derivatives, the 3-methoxy group on the aromatic A-ring of 23 exhibited moderate PI-PLC inhibitory activity (IC(50)=19.7 microM), while compound with a free hydroxyl group (21) was inactive. However, in diaza-pregnane derivatives, epimers with a 3-hydroxyl group (8a, IC(50)=7.4 microM) exhibited more potent PI-PLC inhibitory activity than their counterparts with 3-methoxyl group on the non-aromatic A-ring (26, IC(50)=17.4 microM). We have illustrated in our previous publication that 3-hydroxyl-6-aza steroids are potent PI-PLC inhibitors.(3) However, simultaneous presence of the 6-aza and 22,25-diaza moieties in one molecule as in 13, led to loss of activity. Epimeric mixture 8a showed selective growth inhibition effects in the NCI in vitro tumor cell screen with a mean GI(50) value (MG-MID) of 5.75 microM for 54 tumors.     

Benzoxazole benzenesulfonamides as allosteric inhibitors of fructose-1,6-bisphosphatase

A series of novel benzoxazole benzenesulfonamides was synthesized as inhibitors of fructose-1,6-bisphosphatase (FBPase-1). Extensive SAR studies led to a potent inhibitor, 53, with an IC(50) of 0.57microM. Compound 17 exhibited excellent bioavailability and a good pharmacokinetic profile in rats.     

Synthesis of new pyrrolo[1,2-a]quinoxaline derivatives as potential inhibitors of Akt kinase

Akt kinases are attractive targets for small molecule drug discovery because of their key role in tumor cell survival/proliferation and their overexpression/activation in many human cancers. Recent efforts in the development and biological evaluation of small molecule inhibitors of Akt have led to the identification of novel Akt kinase inhibitors, based on a quinoxaline or pyrazinone scaffold. A series of new substituted pyrrolo[1,2-a]quinoxaline derivatives, structural analogues of these active quinoxaline or pyrazinone pharmacophores, was synthesized from various substituted 2-nitroanilines or 1,2-phenylenediamine via multistep heterocyclization process. These new compounds were tested for their in vitro ability to inhibit the proliferation of the human leukemic cell lines K562, U937 and HL60, and the breast cancer cell line MCF7. Three of these human cell lines (K562, U937 and MCF7) exhibited an active phosphorylated Akt form. The most promising active pyrroloquinoxalines were found to be 1a that inhibited K562 cell line proliferation with an IC(50) of 4.5 microM, and 1h that inhibited U937 and MCF7 cell lines with IC(50) of 5 and 8 microM, respectively. These two candidates exhibited more potent activities than the reference inhibitor A6730.     

Cantharimides: a new class of modified cantharidin analogues inhibiting protein phosphatases 1 and 2A.

Cantharidin and its analogues have been of considerable interest as potent inhibitors of the serine/threonine protein phosphatases 1 and 2A (PP1 and PP2A). However, limited modifications to the parent compounds is tolerated. As part of an on-going study we have developed a new series of cantharidin analogues, the cantharimides. Inhibition studies indicate that cantharimides possessing a D- or L-histidine, are more potent inhibitors of PP1 and PP2A (PP1 IC(50)=3.22+/-0.7 microM; PP2A IC(50)=0.81+/-0.1 microM and PP1 IC(50)=2.82+/-0.6 microM; PP2A IC(50)=1.35+/-0.3 microM, respectively) than norcantharidin (PP1 IC(50)=5.31+/-0.76 microM; PP2A IC(50)=2.9+/-1.04 microM) and essentially equipotent with cantharidin (PP1 IC(50)=3.6+/-0.42 microM; PP2A IC(50)=0.36+/-0.08 microM). Cantharimides with non-polar or acidic amino acid residues are only poor inhibitors of PP1 and PP2A.     

Design, synthesis, and biological evaluation of (E)-3-(4-methanesulfonylphenyl)-2-(aryl)acrylic acids as dual inhibitors of cyclooxygenases and lipoxygenases

A group of (E)-3-(4-methanesulfonylphenyl)acrylic acids possessing a substituted-phenyl ring (4-H, 4-Br, 3-Br, 4-F, 4-OH, 4-OMe, 4-OAc, and 4-NHAc) attached to the acrylic acid C-2 position were prepared using a stereospecific Perkin condensation reaction. A related group of compounds having 4- and 3-(4-isopropyloxyphenyl)phenyl, 4- and 3-(2,4-difluorophenyl)phenyl and 4- and 3-(4-methanesulfonylphenyl)phenyl substituents attached to the acrylic acid C-2 position were also synthesized, using a palladium-catalyzed Suzuki cross-coupling reaction, for evaluation as dual cyclooxygenase-2 (COX-2) and 5-lipoxygenase (5-LOX) inhibitors. (E)-2-(3-Bromophenyl)-3-(4-methanesulfonylphenyl)acrylic acid (9h), and compounds having 4-(4-isopropyloxyphenyl-, 2,4-difluorophenyl-, or 4-methylsulfonylphenyl)phenyl moieties at the acrylic acid C-2 position (11a,b,d), were particularly potent COX-2 inhibitors with a high COX-2 selectivity index (COX-2 IC50 approximately 0.32 microM, SI > 316) similar to the reference drug rofecoxib (COX-2 IC50 = 0.5 microM, SI > 200). Acrylic acid analogs with a C-2 4-hydoxyphenyl (9d, IC50 = 0.56 microM), or 4-acetamidophenyl (9g, IC50 = 0.11 microM), substituent were particularly potent 5-LOX inhibitors that may participate in an additional specific hydrogen-bonding interaction. A number of compounds possessing a C-2 substituted-phenyl moiety (4-Br, 4-F, and 4-OH), or a 4- or 3-(2,4-difluorophenyl)phenyl moiety, showed potent 15-LOX inhibitory activity (IC50 values in the 0.31-0.49 microM range) relative to the reference drug luteolin (IC50 = 3.2 microM). Compounds having a C-2 4-acetylaminophenyl, or 4-(2,4-difluorophenyl)phenyl, moiety exhibited anti-inflammatory activities that were equipotent to aspirin, but less than that of celecoxib. The structure-activity data acquired indicate the acrylic acid moiety constitutes a suitable scaffold (template) to design novel acyclic dual inhibitors of the COX and LOX isozymes.     

Metalloporphyrins are potent inhibitors of lipid peroxidation

The objectives of these studies were to determine whether metalloporphyrins could inhibit lipid peroxidation, characterize factors that influence their potency and compare their potency to prototypical antioxidants. Lipid peroxidation was initiated with iron and ascorbate in rat brain homogenates and the formation of thiobarbituric acid reactive species was used as an index of lipid peroxidation. Metalloporphyrins were found to be a novel and potent class of lipid peroxidation inhibitors. Inhibition of lipid peroxidation by metalloporphyrins was dependent on the transition metal ligated to the porphyrin, indicating that metal centered redox chemistry was important to the mechanism of their antioxidant activities. Manganese porphyrins with the highest superoxide dismutase (SOD) activities, MnOBTM-4-PyP and MnTM-2-PyP (charges are omitted throughout text for clarity), were the most potent inhibitors of lipid peroxidation with calculated IC50s of 1.3 and 1.0 microM, respectively. These manganese porphyrins were 2 orders of magnitude more potent than either trolox (IC50 = 204 microM) or rutin (IC50 = 112 microM). The potencies of the manganese porphyrins were related not only to their redox potentials and SOD activities, but also to other factors that may contribute to their ability to act as electron acceptors. The broad array of antioxidant activities possessed by metalloporphyrins make them attractive therapeutic agents in disease states that involve the overproduction of reactive oxygen species.     

Some new acyclic nucleotide analogues as antiviral prodrugs: synthesis and bioactivities in vitro

A series of ester analogues of acyclic nucleotide PMPA and PMEA were synthesized as potent antiviral agents. The antiviral evaluation results indicated that bis benzyl ester prodrug of PMPA 5f and bis allyl ester prodrug of PMEA 5g exhibited potent antiviral activities. The IC(50) of 5f for HBV was 2.15 microM, and the IC(50) of 5g for HIV-1 was 1.61 microM.     

Synthesis and biological evaluation of 4-amino derivatives of benzimidazoquinoxaline, benzimidazoquinoline, and benzopyrazoloquinazoline as potent IKK inhibitors

We have recently identified BMS-345541 (1) as a highly selective and potent inhibitor of IKK-2 (IC50 = 0.30 microM), which however was considerably less potent against IKK-1 (IC50 = 4.0 microM). In order to further explore the SAR around the imidazoquinoxaline tricyclic structure of 1, we prepared a series of tetracyclic analogues (7, 13, and 18). The synthesis and biological activities of these potent IKK inhibitors are described.     

Identification and optimisation of novel and selective small molecular weight kinase inhibitors of mTOR

A pharmacophore mapping approach, derived from previous experience of PIKK family enzymes, was used to identify a hit series of selective inhibitors of the mammalian target of rapamycin (mTOR). Subsequent refinement of the SAR around this hit series based on a tri-substituted triazine scaffold has led to the discovery of potent and selective inhibitors of mTOR.     

Design, synthesis and biological evaluation of novel chalcone derivatives as antitubulin agents

A series of novel chalcone derivatives have been designed and synthesized, and their biological activities were also evaluated as potential inhibitors of tubulin. These compounds were assayed for growth-inhibitory activity against MCF-7 and A549 cell lines in vitro. Compound 3d showed the most potent antiproliferative activity against MCF-7 and A549 cell lines with IC(50) values of 0.03 and 0.95 μg/mL and exhibited the most potent tubulin inhibitory activity with IC(50) of 1.42 μg/mL. Docking simulation was performed to insert compound 3d into the crystal structure of tubulin at colchicines binding site to determine the probable binding model. Based on the preliminary results, compound 3d with potent inhibitory activity in tumor growth may be a potential anticancer agent.     

Design, synthesis, and biological evaluation of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides as cyclooxygenase isozyme inhibitors

A group of N-acetyl-2-(or 3-)carboxymethylbenzenesulfonamides, possessing either a F or a substituted-phenyl ring substituent (4-F, 2,4-F2, 4-SO2Me, 4-OCHMe2) attached to its C-4 or C-6 position, was prepared using a palladium-catalyzed Suzuki cross-coupling reaction for evaluation as selective cyclooxygenase-2 (COX-2) inhibitors. Although N-acetyl-3-carboxymethyl-6-fluorobenzenesulfonamide [14, COX-1 IC50 = 2.26 microM; COX-2 IC50 = 0.012 microM; COX-2 selectivity index (SI) = 188] and N-acetyl-3-carboxymethyl-6-(4-isopropoxyphenyl)benzenesulfonamide (20c, COX-1 IC50 >100 microM; COX-2 IC50 = 0.15 microM; COX-2 SI >667) exhibited potent in vitro COX-2 inhibitory activity and high COX-2 selectivity, both compounds were inactive anti-inflammatory agents in a carrageenan-induced rat paw edema assay. In contrast, the less potent and less selective COX-2 inhibitors N-acetyl-2-carboxymethyl-4-fluorobenzenesulfonamide (12, COX-1 IC50 = 4.25 microM; COX-2 IC50 = 0.978 microM; COX-2 SI = 4.3), N-acetyl-2-carboxymethyl-4-(2,4-difluorophenyl)benzenesulfonamide (17c, COX-1 IC50 = 1.02 microM; COX-2 IC50 = 1.00 microM; COX-2 SI = 1.02), and N-acetyl-3-carboxymethyl-6-(4-methanesulfonylphenyl)benzenesulfonamide (20e, COX-1 IC50 = 0.109 microM; COX-2 IC50 = 1.14 microM; COX-2 SI = 0.095) exhibited moderate anti-inflammatory activity where a 75 mg/kg oral dose reduced inflammation 26%, 14%, and 20%, respectively, at 3 h postdrug administration relative to the reference drug aspirin where a 50 mg/kg oral dose reduced inflammation by 25% at 3 h postdrug administration.     

Novel 2-amino-4-oxo-5-arylthio-substituted-pyrrolo[2,3-d]pyrimidines as nonclassical antifolate inhibitors of thymidylate synthase

A series of 17 novel 2-amino-4-oxo-5-[(substituted phenyl)thio]pyrrolo[2,3-d]pyrimidines were synthesized as potential inhibitors of thymidylate synthase (TS) and as antitumor agents. The analogues contain a variety of electron withdrawing substituents on the phenyl ring of the side chain and were evaluated as inhibitors of human TS (hTS) and Escherichia coli TS and of human and E. coli dihydrofolate reductase (DHFR). The analogues 14, 17, and 18 were potent inhibitors of hTS with IC50 values of 0.28, 0.21, and 0.22 microM, respectively, and were more potent than the clinically used ZD1694, 2 and LY231514, 3 against human TS.     

Synthesis of celecoxib analogs that possess a N-hydroxypyrid-2(1H)one 5-lipoxygenase pharmacophore: biological evaluation as dual inhibitors of cyclooxygenases and 5-lipoxygenase with anti-inflammatory activity

A hitherto unknown class of celecoxib analogs was designed for evaluation as dual inhibitors of the 5-lipoxygenase/cyclooxygenase-2 (5-LOX/COX-2) enzymes. These compounds possess a SO(2)Me (11a), or SO(2)NH(2) (11b) COX-2 pharmacophore at the para-position of the N(1)-phenyl ring in conjunction with a 5-LOX N-hydroxypyrid-2(1H)one iron-chelating moiety in place of the celecoxib C-5 tolyl group. The title compounds 11a-b are weak inhibitors of the COX-1 and COX-2 isozymes (IC(50)=7.5-13.2 microM range). In contrast, the SO(2)Me (11a, IC(50)=0.35 microM), and SO(2)NH(2) (11b, IC(50)=4.9 microM), compounds are potent inhibitors of the 5-LOX enzyme comparing favorably with the reference drug caffeic acid (5-LOX IC(50)=3.47 microM). The SO(2)Me (11a, ED(50)=66.9 mg/kg po), and SO(2)NH(2) (11b, ED(50)=99.8 mg/kg po) compounds exhibited excellent oral anti-inflammatory (AI) activities being more potent than the non-selective COX-1/COX-2 inhibitor drug aspirin (ED(50)=128.9 mg/kg po) and less potent than the selective COX-2 inhibitor celecoxib (ED(50)=10.8 mg/kg po). The N-hydroxypyridin-2(1H)one moiety constitutes a novel pharmacophore for the design of cyclic hydroxamic mimetics capable of chelating 5-LOX iron for exploitation in the design of 5-LOX inhibitory AI drugs.     

3Beta-hydroxy-6-aza-cholestane and related analogues as phosphatidylinositol specific phospholipase C (PI-PLC) inhibitors with antitumor activity

6-Aza steroid analogues were synthesized as PI-PLC inhibitors. The most active compound, 3beta-hydroxy-6-aza-cholestane (1) showed potent PI-PLC inhibition (IC50 = 1.8 microM), similar to that of the commercially available steroid analogue U73122 (IC50 = 1-2.1 microM). Compound 1 exhibited significant growth inhibition effects (IC50 = 1.3 microM in each case) against MCF-7 and HT-29 cancer cells in in vitro cell culture. Compound 1 also inhibited the in vitro adhesion and transmigration of HT-1080 fibrosarcoma cells at 2.5 and 5.0 microM, respectively. In vivo, compound 1, at 1 mg/kg/day, reduced the volume of MCF-7 tumors in xenograft models, without weight loss in mice. Structure activity relationships of this series of compounds revealed that a hydrophobic cholesteryl side chain, 3beta-hydroxy group and a C-6 nitrogen containing a hydrogen atom at position-6 are crucial for activity. N-Maleic amidoacid derivative 11 also exhibited weak inhibition (IC50 = 16.2 microM).