Synthesis, antitumor and anti-HIV activities of benzodithiazine-dioxides

Several 8-chloro-7-R1-6-R2-3-R3-imidazo[1,2-b][1,4,2]benzodithiazine 5,5-dioxide derivatives (9-11, 16-19, and 21-24) have been synthesized as potential antitumor or anti-HIV agents. The in vitro antitumor and anti-HIV-1 activities of the compounds were determined in a panel of cell lines. The benzodithiazine-dioxide 10 showed 50% growth inhibitory activity in low micromolar against most cells. It was particularly effective in leukemia, lung, melanoma, ovarian, and renal cancer cells with GI50 values of 1-2 microM. Interestingly, benzodithiazine-dioxide 16 showed remarkable anti-HIV-1 activity with 50% effective concentration EC50 value of 0.94 microM and no significant cytotoxicity at 200.0 microM.     

Antimicrobial and cytotoxic arylazoenamines. Part III: antiviral activity of selected classes of arylazoenamines

Eighty-five arylazoenamines, characterized by different types of aryl and basic moieties, have been synthesized and evaluated in cell-based assays for cytotoxicity and antiviral activity against a panel of ten RNA and DNA viruses. The most commonly affected viruses were, in decreasing order, CVB-2, RSV, BVDV, YFV, and Sb-1; the remaining viruses were either not affected (HIV-1, VSV, and VV) or susceptible only to a very few compounds (Reo-1 and HSV-1). Thirty-five compounds exhibited high activity, with EC(50) in the range 0.8-10 microM, and other 28 compounds had EC(50) between 11 and 30 microM, thus indicating that the arylazoenamine molecular pattern is an interesting novel pharmacophore for antiviral agents against ssRNA viruses. Moreover, some compounds (as 28, 32, 42, and 53) appear of high interest, being devoid of toxicity on the human MT-4 cells (CC(50)>100 microM). A ligand-based computational approach was employed to identify highly predictive pharmacophore models for the most frequently affected viruses CVB-2, RSV, and BVDV. These models should allow the design of second generation of more potent inhibitors of these human and veterinary pathogens.     

Synthesis and anti-HIV-1 activity of a novel series of 1,4,2-benzodithiazine-dioxides

Previously, we discovered a series of novel benzodithiazines-dioxides with both antiviral and anticancer activities. In order to design compounds with distinct antiviral properties, we prepared new compounds with modifications on the imidazole and pyrimidine rings. Herein, we present the synthesis and antiviral activity of 8-chloro-2,3-dihydroimidazo[1,2-b][1,4,2]benzodithiazine 5,5-dioxides (22, 23, 30, and 31) and 9-chloro-2,3,4-trihydropyrimido[1,2-b][1,4,2]benzodithiazine 6,6-dioxides (14, 24, 25, and 27). We successfully identified a lead compound with remarkable anti-HIV-1 activity (EC(50)=0.09microM). These compounds showed minimal cytotoxicity and are therefore suitable for antiviral development.     

Antiviral Activities of Marine Pseudomonas Polysaccharides and Their Oversulfated Derivatives

A marine Pseudomonas species WAK-1 strain simultaneously produces extracellular glycosaminoglycan and sulfated polysaccharide. Among the antiviral activities tested for these polysaccharides, the latter showed anti-HSV-1 activity in RPMI 8226 cells (50% effective concentration is 1.4 μg/ml). Oversulfated derivatives of these polysaccharides prepared by dicyclohexylcarbodiimide-mediated reaction for both polysaccharides showed antiviral activities against influenza virus type A (for glycosaminoglycan, 50% effective concentration is 11.0 μg/ml; for another, 2.9 μg/ml). Glycosaminoglycan, sulfated polysaccharide, and their chemically synthesized oversulfated derivatives did not show antiviral activities against influenza virus type B and human immunodeficiency virus type 1. No cytotoxicity of these products was noted against host cells at the 50% cytotoxic concentration of 100 μg/ml, except that naturally occurring sulfated polysaccharide had 50% cytotoxicity against MT-4 cells at 8–21 μg/ml. Received May 1, 1998; accepted July 24, 1998.     

Synthesis and antienteroviral activity of a series of novel, oxime ether-containing pyridyl imidazolidinones

A series of novel, oxime ether-containing pyridyl imidazolidinones were synthesized and their antiviral activity was evaluated in a plaque reduction assay. It is very interesting that this class of compounds is specific for human enteroviruses, in particular, enterovirus 71 (EV71). Some derivatives strongly inhibited enterovirus replication with activities higher or comparable to those of the reference compounds such as A1 and A2. Preliminary SAR studies revealed that the chain length of the alkyl linker and the alkyl substituent at the oxime ether group largely influenced the in vitro anti-EV71 activity of this new class of potent antiviral agents. Among this series of compounds synthesized, the pyridyl imidazolidinone with an ethyl oxime ether group located at the para position of the phenoxyl ring (8b) was identified as the most potent enterovirus 71 inhibitor (IC50=0.001 microM) with no apparent cytotoxic effect toward RD (rhabdomyosarcoma) cell lines (CC50>25 microM). Furthermore, this compound has been shown broad-spectrum activity against most of the serotypes of enteroviruses tested in the nanomolar range.     

Cyclic monophosphate prodrugs of base-modified 2'-C-methyl ribonucleosides as potent inhibitors of hepatitis C virus RNA replication

A new series of heterobase-modified 2'-C-methyl ribonucleosides was synthesized and tested as inhibitors of hepatitis C virus (HCV) RNA replication. The nucleosides showed a weak inhibitory activity in a HCV replicon system (EC(50)=92 microM) and did not exhibit any cytotoxicity (CC(50)>300 microM). Cyclic monophosphate (cMP) prodrugs of the same nucleosides were synthesized and also tested in the HCV replicon system. Prodrugs exhibited strong potency (EC(50)=0.008 microM) without significant cytotoxicity (CC(50)>50 microM).     

Racemic synthesis and antiviral evaluation of 4'(alpha)-hydroxymethyl and 6'(alpha)-methyl substituted apiosyl nucleosides

This article reports the novel synthesis of substituted apiosyl nucleosides. The key apiosyl intermediate 9 was constructed by sequential ozonolysis, reductions, and acetylation from the ester derivative 6. The nucleosides of uracil, thymine, cytosine, and adenine were synthesized using the glycosyl condensation procedure (silyated base and TMSOTf). The antiviral activities of the synthesized compounds against the HIV-1, HSV-1, HSV-2, and HCMV viruses were evaluated. The adenine derivative 26 showed weak anti-HIV activity (EC(50) = 10.1 microg/ml) without exhibiting any cytotoxicity up to a concentration of 100 microM.     

Synthesis and antiviral/antitumor evaluation of 2-amino- and 2-carboxamido-3-arylsulfonylthiophenes and related compounds as a new class of diarylsulfones

Based on general SARs previously described for anti-HIV-1 diarylsulfone derivatives, a series of 2-amino- and 2-carboxamido-3-arylsulfonylthiophenes has been prepared and evaluated as potential antiviral and antitumor agents. In cell culture, some of the 2-aminothiophenes exhibited moderate and selective activity against HIV-1, with 2-amino-3-(2-nitrophenylsulfonyl)thiophene (7e) being most attractive (EC(50)=3.8 microg/mL, CC(50)=>100 microg/mL). In broad-spectrum antiviral assays, the 3-arylsulfonyl-2-(trifluoroacetamido)thiophenes (8c-g) and 2-acetamido-3-arylsulfonyl-5-nitrothiophenes (9f-g) proved considerably active (IC(50)=0.1-10 microg/mL) against human cytomegalovirus (CMV) and/or varicella zoster virus (VZV). Based on the activity of the trifluoroacetamides, ring-modified furan, N-(substituted)pyrrole, phenyl, and 3,4-thiophene analogues were prepared, and these compounds were also active against CMV and/or VZV, with the notable exception of the 3,4-thiophene derivative. In contrast to other amines, the 2-aminopyrrole precursors (13a-d) also exhibited potent activity against CMV. Unfortunately, most of these compounds displayed significant cytotoxicity against human fibroblasts, the cells supporting CMV and VZV replication, and thus selectivity indices were low. The most notable exception to this was the naphthyl-substituted aminopyrrole 13d, which exhibited both potent (IC(50)=0.3 microg/mL) and selective (CC(50)=>50 microg/mL) activity against CMV. Finally, thiophene aryl amides 8i-k displayed moderate in vitro activity against certain leukemia, breast, and colon cancer cell lines.     

The potency of acyclovir can be markedly different in different cell types

Acyclovir is an acyclic guanine analog with a considerable activity against herpes simplex viruses. We studied the antiherpetic activity of acyclovir in macrophages and fibroblast cell lines. Utilising a plaque reduction assay we found that acyclovir potently inhibited the HSV-1 replication in macrophages (EC50) = 0.0025 microM) compared to Vero (EC50 = 8.5 microM) and MRC-5 (EC50 = 3.3 microM) cells. The cytotoxicity of acyclovir was not detected at concentrations < or = 20 microM, thus the selective index in macrophages was >8000. This marked difference in antiherpetic activity between macrophages and fibroblasts was not observed with Foscarnet and PMEA. We suggest that this potent antiviral effect of acyclovir is mainly due to a proficient phosphorylation of the drug and/or a favourable dGTP/acyclovir triphosphate ratio in macrophage cells.     

The novel C-5 aryl, alkenyl, and alkynyl substituted uracil derivatives of L-ascorbic acid: synthesis, cytostatic, and antiviral activity evaluations

The novel C-5 substituted uracil derivatives of l-ascorbic acid were synthesized by coupling of 5-iodouracil-4,5-didehydro-5,6-dideoxy-l-ascorbic acid with unsaturated stannanes under Stille reaction conditions. The new compounds were evaluated for their antitumoral and antiviral activities. Among all compounds evaluated the 5-propynyl substituted uracil derivative of l-ascorbic acid (7) exhibited the most pronounced cytostatic activities against all examined tumor cell lines (IC(50): 0.2-0.78 microM). However, this compound was also cytotoxic to human normal fibroblasts WI 38. The 5-(phenylethynyl)uracil-2,3-di-O-benzylated l-ascorbic acid derivative (4) exhibited an albeit slight (IC(50): 55-108 microM), but selective inhibitory effect toward all tumor cell lines except for cervical carcinoma (HeLa), pancreatic carcinoma (MiaPaCa-2), laryngeal carcinoma (Hep-2), and colon carcinoma (SW 620), and no cytotoxicity to normal human fibroblast (WI 38). Compound 7 showed some, not highly specific, inhibitory potential against vesicular stomatitis virus, Coxsackie B4 virus, and Sindbis viruses (EC(50): 1.6 microM).     

Design, synthesis, and preliminary in vitro and in silico antiviral activity of [4,7]phenantrolines and 1-oxo-1,4-dihydro-[4,7]phenantrolines against single-stranded positive-sense RNA genome viruses

Following the antiviral screening of a wide series of new angular and linear N-tricyclic systems both in silico and in vitro, the [4,7]phenantroline nucleus emerged as a new ring system endowed with activity against viruses containing single-stranded, positive-sense RNA genomes (ssRNA+). Here, we report our new pathway to the synthesis of this nucleus and of several related derivatives, as well as the results of both cell-based antiviral assays and molecular dynamics simulations. In the antiviral screening, several compounds (9 and 16-20) showed to be fairly active against BVDV, CVB-2, and Polio 1 (EC50, 6-25 microM). According to molecular dynamics simulations, compounds (15) and (17) emerged for its potency against the HCV NS5B, with a calculated IC50 of 11-12 microM.     

Zinc coupling potentiates anti-HIV-1 activity of baicalin

Baicalin (BA) has been shown with anti-HIV-1 activity. Zinc is a nutrient element. The anti-HIV-1 activity of zinc complex of baicalin (BA-Zn) in vitro was studied and compared with the anti-HIV-1 activities between BA and BA-Zn in the present study. Our results suggested that BA-Zn has lower cytotoxicity and higher anti-HIV-1 activity compared with those of BA in vitro. The CC50s of BA-Zn and BA were 221.52 and 101.73 microM, respectively. The cytotoxicity of BA-Zn was about 1.2-fold lower than that of BA. The BA and BA-Zn inhibited HIV-1 induced syncytium formation, HIV-1 p24 antigen and HIV-1 RT production. The EC50s of BA-Zn on inhibiting HIV-1 induced syncytium formation (29.08 microM) and RT production (31.17 microM) were lower than those of BA (43.27 and 47.34 microM, respectively). BA-Zn was more effective than BA in inhibiting the activities of recombinant RT and HIV-1 entry into host cells. Zinc coupling enhanced the anti-HIV-1 activity of baicalin.     

Synthesis of new phorbol derivatives having ethereal side chain and evaluation of their anti-HIV activity

Several new phorbol derivatives having ethereal substituents at the 12-position were synthesized and subjected to biological evaluation to find new candidates of an anti-HIV agent. Among them, 12-O-(methoxymethyl)phorbol 13-decanoate showed potent inhibitory activity against infection of HIV-1 in MT-4 cells (EC50: 1.3 ng/mL) and relatively low cytotoxicity (CC50: 8.3 microg/mL). This compound was also found to have sufficient stability in mouse plasma compared with the corresponding 12-acetate derivative, which was an equipotent HIV-1 inhibitor, but with an activity that decreased considerably after plasma treatment.     

Synthesis, cytotoxicity, and DNA topoisomerase II inhibitory activity of benzofuroquinolinediones

Benzofuroquinolinediones (7c and 7d) were synthesized by base-catalyzed condensation of dichloroquinolinediones with phenolic derivatives. Their dialkylaminoalkoxy derivatives (8i-8p) were prepared by reaction with various dialkylaminoalkyl chlorides. The cytotoxicity of the synthesized compounds was evaluated against eight types of human cancer cell lines, and their topoisomerase II inhibition was assessed. In general, the cytotoxicity of benzofuroquinolinediones (8i-8p) was similar or superior to that of doxorubicin and showed more potent inhibitory activity than naphthofurandiones (8a-8h). Also, most of the compounds exhibited excellent topoisomerase II inhibitory activity at a concentration of 5 microM and two compounds, 8d and 8i, showed IC50 values of 1.19 and 0.68 microM, respectively, and were much more potent than etoposide (IC50=78.4 microM), but similar to doxorubicin (IC50=2.67 microM). However their inhibitory activity on topoisomerase I was lower, and 8d and 8i showed IC50 values of 42.0 and 64.3 microM, respectively.     

Tryptamine derivatives as novel non-nucleosidic inhibitors against hepatitis B virus

A series of tryptamine derivatives were synthesized and evaluated for their anti-hepatitis B virus (HBV) activity and cytotoxicity in the HepG2.2.15 cell line. The preliminary SAR was discussed. Compounds 2e and 4a showed potent antiviral activity (IC(50)=0.4 and <1 μM, respectively) and low cytotoxicity (CC(50)=40.6 and >25 μM, respectively).     

Design, synthesis, and biological evaluation of novel 4-hydroxypyrone derivatives as HIV-1 protease inhibitors

Twenty-four 4-hydroxypyrone derivatives were synthesized with a facile synthetic method to develop novel HIV protease inhibitors. Most of them were shown to display good antiviral activities in SIV-infected CEM cells. The introduction of alpha-naphthylmethyl group to C-6 of 5,6-dihydropyran-2-ones led to an effective antiviral compound that showed an EC(50) value at 1.7 microM with a therapeutic index of 46.     

Synthesis of novel 3'-C-methyl-apionucleosides: an asymmetric construction of a quaternary carbon by Claisen rearrangement

The synthesis of 2,3-dideoxy-3-C-(hydroxymethyl)-3-C-methyl-D-glycero-tetrofuranosyl++ + nucleosides was accomplished in high enatiomeric purity (98.5% ee) via [3,3]-sigmatropic Claisen rearrangement of (E)(S)-5-benzyloxy-1-tert-butyldimethylsilanyloxy-4-methyl-pent-3- en-2-ol prepared from 2,3-O-isopropylidene-D-glyceraldehyde. The synthesized nucleosides were assayed against human immunodeficiency virus (HIV) and hepatitis B virus in human peripheral blood mononuclear (PBM) and 2.2.15 cells, respectively. 6-Amino-9-[2,3-dideoxy-3-C-(hydroxymethyl)-3-C-methyl-beta-D-glycero- tetrofuranosyl]-2-fluoropurine shows moderate antiviral activity (EC50 = 2.55 microM) against HIV-1 strains and 6-amino-9-[3-deoxy-3-C-(hydroxymethyl)-3-methyl-alpha-D-glycero-tetro furanosyl]-2-fluoropurine exhibits potent anti-HIV activity (EC50 = 0.073 microM) with significant cytotoxicity (IC50 = 1.0 microM).     

Design, synthesis, and structure-activity relationships of pyrazolo[3,4-d]pyrimidines: a novel class of potent enterovirus inhibitors

A series of pyrazolo[3,4-d]pyrimidines were synthesized and their antiviral activity was evaluated in a plaque reduction assay. It is very interesting that this class of compounds provide remarkable evidence that they are very specific for human enteroviruses, in particular, coxsackieviruses. Some derivatives proved to be highly effective in inhibiting enterovirus replication at nanomolar concentrations. SAR studies revealed that the phenyl group at the N-1 position and the hydrophobic diarylmethyl group at the piperazine largely influenced the in vitro antienteroviral activity of this new class of potent antiviral agents. It was found that the pyrazolo[3,4-d]pyrimidines with a thiophene substituent, such as compounds 20-24, in general exhibited high activity against coxsackievirus B3 (IC(50) = 0.063-0.089 microM) and moderate activity against enterovirus 71 (IC(50) = 0.32-0.65 microM) with no apparent cytotoxic effect toward RD (rhabdomyosarcoma) cell lines (CC(50) > 25 microM).     

Design and evaluation of a potential mutagen for Hepatitis C virus

Pyrrolopyrimidine nucleoside 1 was designed and synthesized as a potential mutagen for HCV. An in vitro HCV NS5B enzymatic assay indicated that pyrrolopyrimidine triphosphate acts as a CTP analog rather than a UTP analog. The SATE-prodrug of pyrrolopyrimidine monophosphate showed a weak inhibitory activity in an HCV replicon system (EC(50)=60 microM) and did not exhibit cytotoxicity (CC(50)>100 microM). Investigation of phosphorylation events using nucleoside kinases and LC-MS analysis revealed that the second phosphorylation step, from monophosphate ester to diphosphate ester, is unfavorable.