No abstract

Hepatitis C virus nonstructural protein 3 (HCV NS3) helicase is believed to be essential for viral replication and has become an attractive target for the development of antiviral drugs. A fluorescence resonant energy transfer helicase assay was established for fast screening of putative inhibitors selected from virtual screening using the program DOCK. Soluble blue HT (1) was first identified as a novel HCV helicase inhibitor. Crystal structure of the NS3 helicase in complex with soluble blue HT shows that the inhibitor bears a significantly higher binding affinity mainly through a 4-sulfonatophenylaminophenyl group, and this is consistent with the activity assay. Subsequently, fragment-based searches were utilized to identify triphenylmethane derivatives for more potent inhibitors. Lead optimization resulted in a 3-bromo-4-hydroxyl substituted derivative 12 with an EC(50) value of 2.72 microM to Ava.5/Huh-7 cells and a lower cytotoxicity to parental Huh-7 cells (CC(50) = 10.5 microM), and it indeed suppressed HCV replication in the HCV replicon cells. Therefore, these inhibitors with structural novelty may serve as a useful scaffold for the discovery of new HCV NS3 helicase inhibitors.

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A series of 2-[(substituted phenylpiperazin-1-yl)methyl]- and 2-[(substituted phenylpiperidin-1-yl)methyl]-2,3-dihydroimidazo[1,2- c]quinazolin-5(6H)-ones or -5(6H)-thiones, and 3-[(substituted phenylpiperazin-1-yl)methyl]-2,3-dihydroimidazo[1,2-c]quinaz oline derivatives were synthesized, as conformationally restricted analogues of SGB-1534 and ketanserin, for evaluation as alpha-antagonists and antihypertensive agents. Most compounds containing a (substituted phenylipiperazinyl)methyl side chain displayed high binding affinity for alpha 1-adrenoceptor with no significant activity at alpha 2-sites. Compounds having a (substituted phenylpiperazinyl)methyl at the 3-position of 2,3-dihydroimidazo[1,2-c]quinazolin-5(6H)-one ring system had a better activity than those with the same substituent at the 2-position. Structure-activity relationships for alpha 1-adrenoceptor affinity are presented and indicate that compounds with substitution at the ortho position on the benzene ring of the phenylpiperazine side chain moiety are more potent than those without substitution and/or substitutions at the 3- and 4-positions. Computer-assisted superimposition of SGB-1534 and 20b showed little structural correspondence between the quinazolinone and 2,3-dihydroimidazo[1,2-c]quinazoline nucleus, and specific interactions of these molecular fragments with the receptor protein appear unlikely. Antihypertensive activity was evaluated via intravenous administration of each compound to spontaneously hypertensive rats, and compounds (16a, 16b, 20b, and 28b) illustrated similar efficacy to SGB-1534 when assessed after 6 h. The pA2 value for 16a against phenylephedrine in rat aorta was much higher than that of prazosin. On the basis of alpha 1-adrenoceptor affinity/selectivity in vitro and duration of antihypertensive action in vivo, compounds 20b and 28b warrant further evaluation.

Aim: To evaluate the effects and elucidate the mechanisms of a series of indoloquinazolines as novel anticancer agents. Methods: Condensation of the substituted isatoic anhydride with the substituted isatin was performed to prepare compounds 1-4, followed by adding malononitrile to prepare compounds 5-7. Cytotoxicity was measured by MTT assays. Apoptosis induction was evaluated using DNA fragmentation, cell cycle assay, caspase 3/7 activity and Western blot. Results: Compounds 3, 4, and 5 display cytotoxicity against MCF-7, HeLa, SKOV3, and A498 cancer cells. DNA ladders appear in cells treated with compounds 3, 4, and 5. Within those, compound 4 exhibits the greatest activity in regards to sub-G 1 accumulations in the cell cycle and the activation of caspase-3/7. Furthermore, Fas and Fas ligand levels are elevated by compound 4, implying that the apoptosis is in part mediated through the signals. On the other hand, compounds 1 and 7 display chemosensitizing activity since cytotoxicity of doxorubicine and etoposide is enhanced in combination with compound 1 and 7, respectively, in MCF-7/adr (doxorubicinresistant) and MCF-7/vp (etoposide-resistant). Conclusion: The cytotoxicity of indoloquinazolines is structure-dependent rather than cell type-dependent due to the similar degree of cytotoxicity induced by the individual compounds in all four cell lines. Further modification of the tryptanthrin skeleton is important to develop novel anticancer agents bearing either cytotoxicity against MCF-7 cells or drug resistance reversal in MCF-7/adr and MCF-7/ vp.

Several nucleosides containing 5Ј-sulfur substituents have been discovered in nature and are involved in many important biological processes. One of the most significant processes is the S-adenosyl-L-methionine (AdoMet)-dependent transmethylations. Inhibition of these methyl transfer processes has been correlated with antiviral activity and has attracted considerable attention as a target for the discovery of new antiviral agents.3,4) S-Adenosyl-L-homocysteine (1, AdoHcy), the byproduct of these AdoMet-dependent transmethylations, and some of its structural analogs have been shown to be potent competitive product inhibitors of the AdoMet-dependent methyltransferases.5-15) Our group has also been interested in the synthesis and biological evaluation of several 5Ј-sulfur containing nucleosides. [16][17][18] In continuation of our studies and our longstanding interest in the biological activities of quinazoline derivatives, 19) we initiated an investigation on the synthesis and biological evaluation of 5Ј-sulfur containing quinazoline nucleoside derivatives.Quinazoline nucleosides were first synthesized by Stout and Robins in 1968 as pyrimidine nucleoside analogs 20) and consequent synthetic studies were contributed by Dunkel and Pfleiderer in the 1990s. [21][22][23] Quinazoline nucleosides were once used as a conformationally restricted model to study the syn-anti conformational preference of pyrimidine nucleosides in solution. 24,25) More recently, quinazoline nucleosides have been incorporated into oligonucleotides as pyrimidine nucleoside substitutes to study the binding affinity and basepairing selectivity.26) However, their biological activities are still relatively less known in literature. 4-Amino-1-(b-D-ribofuranosyl)quinazolin-2-one (3) was chosen for our study. This quinazoline nucleoside was previously synthesized from quinazoline-2,4-dione by Stout and Robins as a cytidine (2) analog, 20) and subsequently shown to display the antiviral activity against herpes simplex virus.27) Other derivatives from this nucleoside have rarely been studied. 20,21) In an effort to explore the antivirial profiles and the chemical properties of the 4-aminoquinazolin-2-one nucleoside (3), two target structures containing 5Ј-sulfur substituents (4, 5) were designed as S-adenosyl-L-homocysteine (1, AdoHcy) analogs. Herein, we report an improved synthesis of 3 and the synthesis of 5Ј-alkylthio-5Ј-deoxy quinazolinone nucleosides 4 and 5. Results and DiscussionA perusal of the literature revealed that most of 4-aminoquinazolin-2-one nucleosides were synthesized by ribosylation of quinazoline-2,4-diones followed by functional group interconversions.20,21) Our first effort was to develop a direct synthetic route from 4-aminoquinazolin-2-one 28,29) (7). The heterocycle 7 was prepared via a 1,3-dicyclohexylcarbodiimide (DCC)-mediated cyclodesulfurative annulation reaction developed in our laboratory.30,31) Anthranilamide (6) was condensed with benzoyl isothiocyanate to form the thiourea intermediate which was immediately treated wi...

In an effort to develop potent human purine nucleoside phosphorylase (PNP) inhibitors as immunosuppressive and chemotherapeutic agents, several 8-aminoguanine derivatives were synthesized and evaluated as potential PNP inhibitors. These studies were designed to investigate the hydrophobic effect of a substituent on the N-9 of the purine heterocycle and/or the C-5' positions. Compounds such as 8-aminoguanosine, guanosine, formycin B, and 8-aminoacyclovir containing a p-(fluorosulfonyl)benzoyl moiety were synthesized. The affinity of these compounds to erythrocytic PNP was determined and none of these compounds showed a better affinity than those of the parent compounds. However, we found that the effect of hydrophobicity at the N-9 and the C-5' positions might play an important role in binding to the active site of PNP. Thus, 8-amino-5'-deoxy-5'-(phenylthio)guanosine (19) was found to be the best inhibitor in this series of compounds with a Ki = 0.45 microM.

Treatment of 5-amino-l-/3-D-ribofuranosylimidazole-4-carboxamide (1, AICA-ribonucleoside) with methoxycarbonyl isothiocyanate followed by cyclodesulfurization of the resulting methoxycarbonylated thioureido derivative with 1,3-dicyclohexylcarbodiimide (DCC) has furnished 5-[3-(methoxycarbonyl)-l-ureido]-l-j3-D-ribofuranosylimidazole-4-carbonitrile ( 6), not 2-[(methoxycarbonyl)amino]-9-fl-D-ribofuranosylpurin-6-one (4). Using 1 labeled with 180 in the carboxamide moiety, the conversion of 1 to 6 is shown to proceed with retention of the 180 label. This finding has suggested the presence of a [l,3]oxazine intermediate in an intramolecular dehydration reaction mechanism. Under similar reaction conditions, methyl 5-amino-l-/3-D-ribofuranosylimidazole-4carboximidate (13) affords 6-methoxy-2-[(methoxycarbonyl)amino]-9-/3-D-ribofuranosylpurine ( 14), which gives guanosine upon deprotection with iodotrimethylsilane. The use of this methoxycarbonyl isothiocyanate/DCC cyclodesulfurization method on heterocyclic o-amino carboximidate esters thus provides a highly efficient entry into the class of guanosine-type nucleoside analogues.