Derivatives of the new ring system indolo[1,2-c]benzo[1,2,3]triazine with potent antitumor and antimicrobial activity.

Derivatives of the new ring system indolo[1,2-c]benzo[1,2,3]triazine 5 were synthesized by diazotization of substituted 2-(2-aminophenyl)indoles followed by an intramolecular coupling reaction of the diazonium group with the indole nitrogen. To obtain the indolobenzotriazine system it was necessary to protect the 3 position of the indole nucleus to avoid cyclization into the indolo[3,2-c]cinnoline system 4. Indolobenzotriazines 5a-g were evaluated in vitro for antitumor activity against a panel of leukemia-, lymphoma-, carcinoma-, and neuroblastoma-derived cell lines. Some compounds inhibited the proliferation of T and B cell lines at submicromolar concentrations, whereas their activity against solid tumor cell lines was in the micromolar range. When evaluated for their antifungal potential 5a,d inhibited some of the fungi tested, although at concentrations very close to those inhibiting the proliferation of human cells. On the contrary, all indolobenzotriazines proved fairly potent and selective inhibitors of Streptococcus and Staphylococcus. In particular 5b,c,g were up to 80 times more potent than the reference drug streptomycin and inhibited the growth of the above Gram-positive bacteria at concentrations far lower than those cytotoxic for animal cells.

Structure-based design, synthesis, and biological evaluation of conformationally restricted novel 2-alkylthio-6-[1-(2,6-difluorophenyl)alkyl]-3,4-dihydro-5-alkylpyrimidin-4(3H)-ones as non-nucleoside inhibitors of HIV-1 reverse transcriptase.

5-Alkyl-2-(alkylthio)-6-(2,6-difluorobenzyl)-3,4-dihydropyrimidin-4(3H)-ones (S-DABOs, 2) have been recently described as a new class of human immunodeficiency virus type 1 (HIV-1) non-nucleoside reverse transcriptase (RT) inhibitors (NNRTIs) active at nanomolar concentrations (Mai, A. et al. J. Med. Chem. 1999, 42, 619-627). In pursuing our lead optimization efforts, we designed novel conformationally restricted S-DABOs, 3, featuring a methyl at the benzylic carbon (Y = Me) and at the pyrimidine 5-position (R = Me). Conformational analyses and docking simulations suggested that the presence of both methyls would significantly reduce conformational flexibility without compromising, in the R enantiomers, the capability of fitting into the RT non-nucleoside binding pocket. To develop structure-activity relationships, we prepared several congeners of type 3 belonging to the thymine (R = Me) and uracil (R = H) series, featuring various 2-alkylthio side chains (X = Me, i-Pr, n-Bu, i-Bu, s-Bu, c-pentyl, and c-hexyl) and aryl moieties different from the 2,6-difluorophenyl (Ar = phenyl, 2,6-dichlorophenyl, 1-naphthyl). Moreover, alpha-ethyl derivatives (Y = Et) were included in the synthetic project in addition to alpha-methyl derivatives (Y = Me). All of the new compounds were evaluated for their cytotoxicity and anti-HIV-1 activity in MT-4 cells, and some of them were assayed against highly purified recombinant wild-type HIV-1 RT using homopolymeric template primers. The results were expressed as CC(50) (cytotoxicity), EC(50) (anti-HIV-1 activity), SI (selectivity, given by the CC(50)/EC(50) ratio), and IC(50) (RT inhibitory activity) values. In the 2,6-difluorobenzylthymine (R = Me) series, methylation of the benzylic carbon improved anti-HIV-1 and RT inhibitory activities together with selectivity. Compound 3w (Ar = 2,6-F(2)-Ph, R = Y = Me, X = c-pentyl) turned out the most potent and selective among the S-DABOs reported to date (CC(50) > 200 microM, EC(50) = 6 nM, IC(50) = 5 nM, and SI > 33 333). Assays performed on the pure enantiomer (+)-3w, much more active than (-)-3w, yielded the following results: CC(50) > 200 microM, EC(50) = 2 nM, IC(50) = 8 nM, and SI > 100 000, under conditions wherein MKC-442 was less active and selective (CC(50) > 200 microM, EC(50) = 30 nM, IC(50) = 40 nM, SI > 6666). The 2,6-difluorophenylethylthymines (R = Me) were generally endowed with higher potency compared with the uracil counterparts (R = H). In the 2,6-difluorophenyl series the best and the least performant 2-alkylthio side chains were the 2-c-pentylthio and the 2-methylthio, respectively. When the methyl at the benzylic carbon was replaced by an ethyl, activity was retained or decreased slightly, thus suggesting that the dimensions of the cavity within the RT hosting this substituent would not be compatible with groups larger than ethyl. Aryl moieties different from the 2,6-difluorophenyl (phenyl, 1-naphthyl, 2,6-dichlorophenyl) were generally detrimental to activity, consistent with a favorable electronic effect exerted by the 2,6-fluorines on a putative charge-transfer interaction between the aromatic moieties of the inhibitor and Tyr188.

Phthalein derivatives as a new tool for selectivity in thymidylate synthase inhibition.

A new set of phthalein derivatives stemming from the lead compound, phenolphthalein, were designed to specifically complement structural features of a bacterial form of thymidylate synthase (Lactobacillus casei, LcTS) versus the human TS (hTS) enzyme. The new compounds were screened for their activity and their specificity against TS enzymes from different species, namely, L. casei (LcTS), Pneumocystis carinii (PcTS), Cryptococcus neoformans (CnTS), and human thymidylate synthase (hTS). Apparent inhibition constants (Ki) for all the compounds against LcTS were determined, and inhibition factors (IF, ratio between the initial rates of the enzymatic reaction in the presence and absence of each inhibitor) against each of the four TS species were measured. A strong correlation was found between the two activity parameters, IF and Ki, and therefore the simpler IF was used as a screening factor in order to accelerate biological evaluation. Compounds 5b, 5c, 5ba, and 6bc showed substantial inhibition of LcTS while remaining largely inactive against hTS, illustrating for the first time remarkable species specificity among TSs. Due to sequence homology between the enzymes, several compounds also showed high activity and specificity for CnTS. In particular, 3-hydroxy-3-(3-chloro-4-hydroxyphenyl)-6-nitro-1H, 3H-naphtho[1,8-c,d]pyran-1-one (6bc) showed an IF < 0.04 for CnTS (Ki = 0.45 microM) while remaining inactive in the hTS assay at the maximum solubility concentration of the compound (200 microM). In cell culture assays most of the compounds were found to be noncytotoxic to human cell lines but were cytotoxic against several species of Gram-positive bacteria. These results are consistent with the enzymatic assays. Intriguingly, several compounds also had selective activity against Cr. neoformans in cell culture assay. In general, the most active and selective compounds against the Gram-positive bacteria were those designed and found in the enzyme assay to be specific for LcTS versus hTS. The original lead compound was least selective against most of the cell lines tested. To our knowledge these compounds are the first TS inhibitors selective for bacterial TS with respect to hTS.

DABOs as candidates to prevent mucosal HIV transmission.

Worldwide, the heterosexual route is the prevalent mode of transmission of AIDS; therefore, demands have been raised for measures that block sexual spreading of the HIV infection. Development of microbicides for topical use may represent an efficacious alternative to condoms. Several approaches are being investigated. Besides surfactants, which directly act on the virus particle, and measures that enhance natural defence mechanisms, promising new candidates appear to be drugs that block the early steps of HIV multiplication. We describe herein a long-term assay which enables the establishment of whether the above drugs reversibly (virustatic action) or irreversibly (virucidal action) inhibit HIV-1 multiplication, thus allowing screening for effective and potent microbicides. We validated our assay with nucleoside (NRTIs) and non-nucleoside reverse transcriptase inhibitors (NNRTIs). Following a chronic treatment, the NRTIs tested (didanosine, zalcitabine, stavudine and lamivudine) simply delayed the viral breakthrough with respect to infected, untreated controls. Under the same experimental conditions, non-nucleoside reveres transcriptase inhibitors (NNRTIs), such as MKC-442, alphaAPA, nevirapine, efavirenz and 3,4-dihydro-2-alkoxy-6-benzyl-4-oxopyrimidines (DABOs) MC 1047 and MC 1220 suppressed HIV-1 replication for the entire experimental period (40 days). When cell culture samples were evaluated for the presence of infectious virus, p24 antigen and viral DNA sequences, none of them was detected up to day 40 post-infection (p.i.). Identical results were obtained after a treatment with the above NNRTIs limited to the first 4 days p.i. Under more selective experimental conditions, that is drug treatments limited to the first 4 h p.i., nevirapine and efavirenz proved to be virustatic; in fact, viral breakthrough ensued shortly after their removal from the culture medium. Conversely, DABO MC 1220 was endowed with potent virucidal activity; in fact, at 3.5 microM it was able to suppress HIV-1 multiplication in cultures acutely infected with a very high multiplicity of infection (5 CCID50/cell), thus allowing exponential cell multiplication as in uninfected cultures for the next 40 days.

Synthesis and antiproliferative activity of 2-triazenothiophenes.

A series of 2-triazenothiophene derivatives was prepared and tested to evaluate their biological activity. Two compounds inhibited the proliferation of leukemia, lymphoma and solid tumor-derived cell lines at micromolar concentrations, whereas none of the compounds were active against HIV-1. Compound 3c inhibited DNA, RNA and protein synthesis, and was also effective against KB cells resistant to etoposide and vincristine. The compounds were inactive against fungi and bacteria.

Synthesis and biological evaluation of azole derivatives, analogues of bifonazole, with a phenylisoxazolyl or phenylpyrimidinyl moiety.

A series of azole derivatives, isoxazole or pyrimidine analogues of the antifungal drug bifonazole, were synthesized and tested in vitro against representative human pathogenic fungi (Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus). They were also evaluated as antibacterial agents against Staphylococcus aureus and Salmonella spp. Only 5-(imidazol-1-yl-phenylmethyl)-2,4-diphenyl-pyrimidine 7c showed weak antimicrobial activity (MIC = 66 microM) against C. albicans, C. neoformans and S. aureus. Results of biological tests proved, therefore, that replacement of the biphenyl portion of the bifonazole with a phenylisoxazolyl or phenylpyrimidinyl moiety is not profitable for antimicrobial properties.

3,6-Disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazoles: synthesis and evaluation for antimicrobial and antiviral activity. III.

A series of novel 3,6-disubstituted 1,2,4-triazolo[3,4-b][1,3,4]thiadiazole derivatives was prepared and tested to evaluate their antimycotic, antibacterial and anti-HIV-1 activities. The reaction of thiocarbohydrazide with carboxylic acids at the melting temperature allows an improved preparation of the 5-substituted 4-amino-3-mercapto-1,2,4-triazole heterocycles which in turn allows an easier preparation of the 1,2,4-triazolo[3,4-b] [1,3,4]thiadiazole ring system. All tested compounds didn't show any significant activity.

Acyclic glycosidopyrroles analogues of ganciclovir: synthesis and biological activity.

Acyclic glycosidopyrroles of type 3 were synthetized in good overall yields, according to the Scheme. When evaluated for antiviral activity against DNA and RNA viruses, only compound in which R1 = R2 = Ph, R3 = NH2 was found to inhibit the HIV-1 replication at concentrations that were not cytotoxic for MT-4 cells.

Synthesis and biological evaluation of [alpha-(1,5-disubstituted 1H-pyrazol-4-yl)benzyl]azoles, analogues of bifonazole.

A series of pyrazole analogues of bifonazole, an antifungal drug used in clinical practice, 2a-h and 4a-h were synthesized and tested in vitro against Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus, with no significant results. Imidazoles 2a-h were also tested in vivo for antiarrhythmic and antihypertensive activities; two of these compounds showed moderate activity against ventricular fibrillation caused by aconitine in rats. The above compounds were prepared by reaction of phenyl-[5 substituted 1-phenyl (or 1-methyl)-1H-pyrazol-4-yl]methanols with N,N'-carbonyldiimidazole (2a-h) or of the respective chloro derivatives with 1H-1,2,4-triazole (4a-h).

Glycosidopyrroles. Part 3. Effect of the benzocondensation on acyclic derivatives: 1-(2-hydroxyethoxy) methylindoles as potential antiviral agents.

The new of 1-(2-hydroxyethoxy)methylindole derivatives 3a-i were prepared in good yields. None of them showed any significant anti-HIV activity and therefore the benzocondensation between the 2 and 3 positions of the pyrrole ring definitely reduced the weak activity found in the analogues 1a-c.

Glycosidopyrroles. Part 2. Acyclic derivatives: 1-(1,3-dihydroxy-2-propoxy)methylpyrroles as potential antiviral agents.

The series of 1-(1,3-dihydroxy-2-propoxy)methylpyrroles 2a-o were prepared in good overall yields according to Scheme I. When evaluated for antiviral activity against HIV-1, only compounds of the triphenyl series (R3 = NH2, N3, Br) were found to inhibit the HIV-1 replication at concentrations that were very not cytotoxic for MT-4 cells, with selectivity index 1.5-9.3. None of these compounds showed antibacterial or antifungal activity.

Azole antifungal agents related to naftifine and butenafine.

The methyl group of naftifine (1) and butenafine (2) was replaced by an azolic nucleus to obtain the new compounds 3-8 which exhibit the characteristics of both allylamine (or benzylamine) and azole antifungals. The title compounds were evaluated in vitro against several pathogenic fungi responsible for human disease. Among these, compounds 5, 6, and 8 were found to inhibit the growth of dermatophytes with a potency comparable to that of naftifine. The synthetic sequence includes the preparation of aminoazole Schiff bases, reduction, and alkylation of the corresponding secondary amines.

A new class of antifungal agents. Synthesis and antimycotic activity of disubstituted N-azolylamines.

In this study we extended our exploration of the N-azolylamine moiety for its antifungal activity. We prepared a number of N-azolylamino derivatives. The synthetic sequence includes the preparation of aminoazole Schiff bases, and the reduction and the alkylation of the corresponding secondary amines. The title compounds were evaluated in vitro against several pathogenic fungi responsible for human disease. The most potent antimicrobial compound was the N-(biphenyl-4-yl)methyl-N-(2,4-dichlorophenyl)methyl-1H-imidazol-l-yl amine (21), which was found to be active against yeasts and dermatophytes; its potency and selectivity were comparable to those of miconazole.

Nitroquinolones with broad-spectrum antimycobacterial activity in vitro.

During search on quinolonecarboxylic acids we used a facile, convenient two- or three-step procedure to synthesize new quinolone analogs, bearing at the C-7 position alkylamino substituents, and at the C-6 position a fluorine or alternatively a nitro group. The new derivatives were tested against both Gram-positive and Gram-negative bacteria and against a number of different mycobacteria. In vitro assays showed 1-tert-butyl-7-tert-butylamino-6-nitro-1,4-dihydro-4-quinolone-3-carboxy lic acid to be a potent inhibitor of Streptococcus and Staphylococcus with potencies superior to those of ofloxacin and ciprofloxacin, used as reference drugs. Some 6-nitroquinolones were found to exert good inhibiting activities against Mycobacterium tuberculosis and various atypical mycobacteria, whereas the 6-fluoro counterparts showed poor or no activity against this bacterium.

Synthesis and biological evaluation of a series of substituted pyrazolo[3,4-d]-1,2,3-triazoles and pyrazolo[3,4-d]oxazoles.

In view of the biological relevance of triazole-based heterocyclic structures as antifungal, antiviral, and antitumor agents, we have synthesized a series of substituted pyrazolo[3,4-d]-1,2,3-triazoles (2e-h, 2j, 4b) which we evaluated for their cytostatic and antiviral (HIV-1 included) activity and for their capability to inhibit the multiplication of various human pathogenic fungi and bacteria. Moreover, the biological activities of a few compounds, namely pyrazolo[3,4-d]oxazoles (3a-e) and pyrazolo[3,4-d]-1,2,3-triazoles (2a-d, 4a, 5), previously obtained by us but not investigated for their biological activity, were also studied. Only compounds 3a-e were endowed with a significative antiproliferative activity on the human lymphoblastoid cell line MT-4 cells. All pyrazole derivatives proved ineffective in protecting cell cultures against the HIV-1-induced cytopathogenicity, and none of the compounds was active against the bacteria and fungi tested.

Synthesis and antimicrobial activity of new 3-(1-R-3(5)-methyl-4-nitroso-1H-5(3)-pyrazolyl)-5-methylisoxazoles.

A number of new 3-(1-R-3(5)-methyl-4-nitroso-1H-5(3)-pyrazolyl)-5-methylisoxazoles 6a-g (7b-f) were synthesized and tested for antibacterial and antifungal activity. Some of these compounds displayed antifungal activity at non-cytotoxic concentrations. Derivative 6c was 9 times more potent in vitro than miconazole and 20 times more selective against C. neoformans. 6c was also 8- and 125-fold more potent than amphotericin B and fluconazole, respectively. None of the compounds was active against bacteria. Preliminary structure-activity relationship (SAR) studies showed that the NO group at position 4 of the pyrazole ring is essential for the activity. Lipophilicity of the pyrazole moiety, N-alkyl chain length and planarity of the two heterocyclic rings appear to play a decisive role in modulating cytotoxicity and antifungal activity.

Peptide T-araC conjugates: solid-phase synthesis and biological activity of N4-(acylpeptidyl)-araC.

Due to the capability of peptidyl derivatives of araC to behave as prodrugs of this antimetabolite, and because of the well known biological properties of peptide T and its analogues (in particular that of targeting CD4+ cells), new peptide T-araC conjugates were prepared and tested in vitro for antiproliferative activity. The aim was that of specifically delivering the antitumor drug to CD4+ cells. N4-(Acylpeptidyl)-derivatives of araC were synthesized by a new general approach involving solid-phase synthesis, which allows mild conditions, avoids the usually required protection of the glycoside portion of nucleosides and affords high yields of the final products. After the demonstration that peptide T-araC conjugates were able to activate chemotaxis by binding CD4 receptor on monocyte membranes, the antiproliferative activity was evaluated against a panel of leukemia lymphoma and carcinoma cell lines derived from human tumors, three CD4+ cell lines included. Title compounds resulted effective as antiproliferative agents at concentrations 4- to 10-fold higher than those of araC alone, did not preferentially inhibit CD4+ cells and proved stable not only in cell culture medium containing 20% FCS, but also in human plasma. All this suggests their potential utility in vivo.

Indolo[3,2-c]cinnolines with antiproliferative, antifungal, and antibacterial activity.

A series of indolo[3,2-c]cinnoline derivatives was prepared and tested to evaluate their biological activity. Most of them inhibited the proliferation of leukemia, lymphoma and solid tumor-derived cell lines at micromolar concentrations, whereas none of the compounds were active against HIV-1. With the exception of 7g, all title compounds showed antibacterial activity against gram-positive bacteria, being up to 200 times more potent than the reference drug streptomycin. Some of the indolo[3,2-c]cinnolines were also endowed with good antifungal activity, particularly against Criptococcus neoformans.

Synthesis, antiviral and antiproliferative activity of a new class of 5-(alkyl or arylthio)-6-vinyl uracils.

Uracil derivatives bearing substituted or unsubstituted vinyl groups at position C6 and alkyl- or arylthio groups at position C5 were synthesized and tested in vitro for antiviral and antiproliferative activity. None of the compounds were active against HIV-1. However, some of them inhibited the proliferation of leukemia, lymphoma and solid tumor-derived cell lines at micromolar concentrations. The maximum potency of antiproliferative activity correlates with the presence of unsubstituted vinyl groups and alkyl- or arylthio substituents.