Bis-cationic heteroaromatics as macrofilaricides: synthesis of bis-amidine and bis-guanylhydrazone derivatives of substituted imidazo[1,2-a]pyridines

Iodine Promoted Efficient Synthesis of 2-Arylimidazo[1,2-a]pyridines in Aqueous Media: A Comparative Study between Micellar Catalysis and an "On-Water" Platform

In a new and environmentally sustainable approach, a series of 2-arylimidazo[1,2-a]pyridine derivatives were synthesized in aqueous media in the presence of iodine as a catalyst. The reaction proceeded by condensation of various aryl methyl ketones with 2-aminopyridines to afford 2-arylimidazo[1,2-a]pyridines in good overall yields. Although several of the reactions were efficiently performed "on water", the addition of a surfactant, namely, sodium dodecyl sulphate , was found effective in terms of substrate scope and yield enhancement. Both methods were successfully used for the gram-scale synthesis of a marketed drug, zolimidine. The simple experimental setup, water as "green" media, and inexpensive catalyst are some of the merits of this protocol.

Data on synthesis, ADME and pharmacological properties and early safety pharmacology evaluation of a series of novel NURR1/NOT agonist potentially useful for the treatment of Parkinson's disease

This article describes the chemical synthesis, ADME and pharmacological properties and early safety pharmacology evaluation of a series of novel Nurr1/NOT agonist. It is meant as a support to an article recently published in Bioorganic and Medicinal chemistry Letters and entitled “Development of a novel NURR1/NOT agonist from hit to lead and candidate for the potential treatment of Parkinson's disease” [1] and presenting the discovery, scope and potential of these new ligands of these nuclear receptors.

Single photon emission computed tomography/positron emission tomography imaging and targeted radionuclide therapy of melanoma: new multimodal fluorinated and iodinated radiotracers

This study reports a series of 14 new iodinated and fluorinated compounds offering both early imaging ((123)I, (124)I, (18)F) and systemic treatment ((131)I) of melanoma potentialities. The biodistribution of each (125)I-labeled tracer was evaluated in a model of melanoma B16F0-bearing mice, using in vivo serial γ scintigraphic imaging. Among this series, [(125)I]56 emerged as the most promising compound in terms of specific tumoral uptake and in vivo kinetic profile. To validate our multimodality concept, the radiosynthesis of [(18)F]56 was then optimized and this radiotracer has been successfully investigated for in vivo PET imaging of melanoma in B16F0- and B16F10-bearing mouse model. The therapeutic efficacy of [(131)I]56 was then evaluated in mice bearing subcutaneous B16F0 melanoma, and a significant slow down in tumoral growth was demonstrated. These data support further development of 56 for PET imaging ((18)F, (124)I) and targeted radionuclide therapy ((131)I) of melanoma using a single chemical structure.

Towards novel antifilarial drugs: challenges and recent developments

Filariasis is caused by thread-like nematode worms, classified according to their presence in the vertebrate host. The cutaneous group includes Onchocerca volvulus, Loa loa and Mansonella streptocerca; the lymphatic group includes Wuchereria bancrofti, Brugia malayi and Brugia timori and the body cavity group includes Mansonella perstans and Mansonella ozzardi. Lymphatic filariasis, a mosquito-borne disease, is one of the most prevalent diseases in tropical and subtropical countries and is accompanied by a number of pathological conditions. In recent years, there has been rapid progress in filariasis research, which has provided new insights into the pathogenesis of filarial disease, diagnosis, chemotherapy, the host–parasite relationship and the genomics of the parasite. Together, these insights are assisting the identification of novel drug targets and the discovery of antifilarial agents and candidate vaccine molecules. This review discusses the antifilarial activity of various chemical entities, the merits and demerits of antifilarial drugs currently in use, their mechanisms of action, in addition to antifilarial drug targets and their validation.

Evaluation of radiolabeled (hetero)aromatic analogues of N-(2-diethylaminoethyl)-4-iodobenzamide for imaging and targeted radionuclide therapy of melanoma

Targeted radionuclide therapy using radioiodinated compounds with a specific affinity for melanoma tissue is a promising treatment for disseminated melanoma, but the candidate with the ideal kinetic profile remains to be discovered. Targeted radionuclide therapy concentrates the effects on tumor cells, thereby increasing the efficacy and decreasing the morbidity of radiotherapy. In this context, analogues of N-(2-diethylaminoethyl)-4-iodobenzamide (BZA) are of interest. Various (hetero)aromatic analogues 5 of BZA were synthesized and radioiodinated with (125)I, and their biodistribution in melanoma-bearing mice was studied after i.v. administration. Most [ (125)I] 5-labeled compounds appeared to bind specifically and with moderate-to-high affinity to melanoma tumor. Two compounds, 5h and 5k, stood out with high specific and long-lasting uptake in the tumor, with a 7- and 16-fold higher value than BZA at 72 h, respectively, and kinetic profiles that makes them promising agents for internal targeted radionuclide therapy of melanoma.

Synthesis and antiprotozoal activity of novel bis-benzamidino imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridines

The key dinitrile intermediates 4a-d were synthesized by reaction of phenacyl bromide 1 and the appropriate 2-amino-5-bromopyridines to yield 3a-d. Suzuki coupling of 3a-d with 4-cyanophenylboronic acid yielded the 2,6-bis(4-cyanophenyl)-imidazo[1,2-a]pyridine derivatives 4a-d. The bis-amidoximes 5a-d, obtained from 4a-d by the action of hydroxylamine, were converted to the bis-O-acetoxyamidoximes which on catalytic hydrogenation in a mixture of ethanol/ethyl acetate gave the acetate salts of 2,6-bis[4-(amidinophenyl)]-imidazo[1,2-a]pyridines 7a-d. In contrast, catalytic hydrogenation of the bis-O-acetoxyamidoxime of 5a in glacial acetic acid gave the saturated analogue 2,6-bis[4-(amidinophenyl)]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine 8. O-Methylation of the amidoximes 5a-d gave the N-methoxyamidines 6a-d. The diamidines showed strong DNA binding affinity, were very active in vitro against T. b. r. exhibiting IC(50) values between 7 and 38nM, but were less effective against P. f. with IC(50) values between 23 and 92nM. Two of the diamidines 7c and 7d were slightly more active than furamidine but less active than azafuramidine in the T. b. r. STIB900 mouse model. Only one prodrug 6b showed moderate activity in the same mouse model.

Chemotherapy for lymphatic filariasis: progress but not perfection

Currently, only three drugs are used to control and treat the mosquito-borne parasitic disease lymphatic filariasis: diethylcarbamazine, ivermectin (Mectizan) and albendazole (Zentel). All interrupt transmission by eliminating microfilaria, the parasite stage that is responsible for transmission between hosts, but do not reliably kill the adult worms that are responsible for much of the pathology seen in the disease. There is an urgent need to develop drugs that will reliably kill adult worms and several compounds are under-going in vitro and animal testing. An alternative strategy - that of targeting symbiont bacteria within the parasite - has also shown promising results.

Novel dicationic imidazo[1,2-a]pyridines and 5,6,7,8-tetrahydro-imidazo[1,2-a]pyridines as antiprotozoal agents

2-[5-(4-Amidinophenyl)-furan-2-yl]-5,6,7,8-tetrahydro-imidazo[1,2-a]pyridine-6-carboxamidine acetate salt (7) was synthesized from 2-[5-(4-cyanophenyl)-furan-2-yl]-imidazo[1,2-a]pyridine-6-carbonitrile (4a), through the bis-O-acetoxyamidoxime followed by hydrogenation in glacial acetic acid. Compound 4a was obtained in four steps starting with two successive brominations of 2-acetylfuran first with N-bromosuccinimide, and second with bromine to form alpha-bromo-2-acetyl-5-bromofuran (2) in a moderate yield. The product (3a), of the condensation reaction between 6-amino-nicotinonitrile and 2, undergoes Suzuki coupling with 4-cyanophenylboronic acid to furnish 4a in good yield. Acetate salt of 2-[5-(4-amidinophenyl)-furan-2-yl]-imidazo[1,2-a]pyridine-6-carboxamidine (8a) was obtained from 4a, through the bis-O-acetoxyamidoxime followed by hydrogenation in a mixture of ethanol/ethyl acetate. N-Methoxy-2-(5-[4-(N-methoxyamidino)-phenyl]-furan-2-yl)-imidazo[1,2-a]pyridine-6-carboxamidine (6) was prepared via methylation of the respective diamidoxime 5a with dimethyl sulfate. By these approaches eight new diamidines and four potential prodrugs were prepared. All of the diamidines showed strong DNA affinities as judged by high DeltaT(m) values. Six of the eight diamidines gave in vitro IC(50) values of 63 nM or less vs T. b. rhodesiense with two exhibiting values of 6 nM and 1 nM. Also, six of the eight diamidines gave in vitro IC(50) values of 88 nM or less vs P. falciparum with two exhibiting values of 14 nM. Excellent in vivo activity in the trypanosomal STIB900 mouse model was found for five of the diamidines on ip dosage; these compounds gave 4/4 cures in this model. The oral activity of the prodrugs was modest with only one showing 2/4 cures in the same mouse model.

Syntheses of α-Fluoro-α,β-unsaturated Thioamides and Thiazolines from a Fluorophosphonodithioacetate

A high-yielding synthesis of methyl fluoro(diethoxyphosphono)dithioacetate starting from its difluorinated analogue is reported. Fluorophosphonothioacetamides and -methylthiazolines, prepared from this new dithioester, have been successfully transformed into highly functionalized fluoroalkenes. Good stereoselectivity in favor of the E isomer was observed from the fluorophosphonomethylthiazolines. The potential of these new fluorinated olefinating reagents for the synthesis of modified peptides and glycosides is also disclosed.

Novel diphenylalkyl piperazine derivatives with dual calcium antagonistic and antioxidative activities

Two types of novel diphenylalkyl piperazine derivatives containing the thio or aminopropanol moiety substituted by phenyl or benzyl group were synthesized, and evaluated for their calcium antagonistic and antioxidative activities. These compounds showed apparent inhibitions against KCl-induced contractions in isolated rat aorta. Among them, phenylamino compound 9 and benzylamino compound 13 also possessed potent inhibitory activities against auto-oxidative lipid peroxidations in canine brain homogenates. Two representative compounds 3a and 9 were evaluated for their inhibitory activities against KCl-induced contractions in isolated canine arteries (basilar, coronary, mesenteric, and renal). Both compounds showed the most potent inhibitions to basilar artery.

Synthesis, structure investigations, and antimicrobial activity of selected s-trans-6-aryl-4-isopropyl-2-[2-[(E)-1-phenylalkylidene]-(E)-hydrazino]-1,4-dihydropyrimidine hydrochlorides

A series of 6-aryl-4-isopropyl-2-[2-(1-phenylalkylidene)hydrazino]-1,4-dihydropyrimidine hydrochlorides was prepared and tested for antibacterial and antifungal effects. The title compounds were synthesized by cyclocondensation of N(2)-(1-phenylalkylideneamino)guanidines with 1-aryl-4-methyl-2-penten-1-ones. Structure analyses of the prepared compounds were accomplished by means of 1D and 2D NMR spectroscopy. The analyses showed that the ring closure reaction took place regioselectively in all cases and generated exclusively 2-(phenylalkylidenehydrazino)dihydropyrimidines. According to the NOE experiments, the applied N(2)-(1-phenylalkylideneamino)guanidines exist in [D(6)]DMSO solution as s-trans-(E)- and the title compounds as s-trans-(E,E)-isomers. The antimicrobial activity was evaluated against representative Gram-negative and Gram-positive bacteria, and against the pathogenic yeast Candida albicans. The tested title compounds showed weak antibacterial activity against Gram-positive bacteria, and one compound was active against Candida albicans.