The antifungal activity of sulfonylamido derivatives of 2-aminophenoxathiin and related compounds

Recent advances in antifungal drug development targeting lanosterol 14α-demethylase (CYP51): A comprehensive review with structural and molecular insights

Fungal infections are posing serious threat to healthcare system due to emerging resistance among available antifungal agents. Among available antifungal agents in clinical practice, azoles (diazole, 1,2,4-triazole and tetrazole) remained most effective and widely prescribed antifungal agents. Now their associated side effects and emerging resistance pattern raised a need of new and potent antifungal agents. Lanosterol 14α-demethylase (CYP51) is responsible for the oxidative removal of 14α-methyl group of sterol precursors lanosterol and 24(28)-methylene-24,25-dihydrolanosterol in ergosterol biosynthesis hence an essential component of fungal life cycle and prominent target for antifungal drug development. This review will shed light on various azole- as well as non-azoles-based derivatives as potential antifungal agents that target fungal CYP51. Review will provide deep insight about structure activity relationship, pharmacological outcomes, and interactions of derivatives with CYP51 at molecular level. It will help medicinal chemists working on antifungal development in designing more rational, potent, and safer antifungal agents by targeting fungal CYP51 for tackling emerging antifungal drug resistance.

Synthesis of phenoxathiins using an iron-catalysed C-H thioarylation

Phenoxathiins are an important class of sulfur-containing heterocycle, found as the core component in numerous pharmaceutically active agents and materials. Despite this importance, there are relatively few methods for the synthesis of these heterocycles that avoid complex starting materials, harsh conditions or precious transition metals. We report a two-step synthesis of phenoxathiins from phenols using iron and copper-mediated reactions. The first step involves the accelerated ortho-thioarylation of phenols using N-(2-bromophenylthio)succinimide, catalysed by the Lewis acid, iron(III) triflimide and the Lewis base, bis(4-methoxyphenyl)sulfane. In the second step, the thioarylated products were converted to a series of phenoxathiins using a copper-mediated, Ullmann-type, C-O bond forming cyclisation reaction. The synthetic utility of this two-step approach for the preparation of biologically relevant phenoxathiins was demonstrated using natural product-based phenols.

Acid-Mediated Sulfonylthiolation of Arenes via Selective Activation of SS-Morpholino Dithiosulfonate

A trifluoroacetic-acid-mediated desulfurilative sulfonylthiolation of arenes using SS-morpholino dithiosulfonate is described. This system is based on selective activation of the morpholino group over the tosyl group of the doubly transformable sulfur surrogate. Mechanistic studies suggested that the reaction proceeds through electrophilic aromatic substitution followed by sulfur extrusion. The wide substrate scope of this reaction and the transformability of the resulting thiosulfonates enable expeditious access to divergent multifunctionalized sulfides.

Study on reactions of long-lived phenoxathiin radical cation with aliphatic alcohols, phenol and phenyl halides in ambient condition by fused-droplet electrospray ionization mass spectrometry

he reactions of phenoxathiin radical cations with diverse organic compounds in ambient conditions were realized by using fused-droplet electrospray ionization mass spectrometry. In the investigation, the phenoxathiin radical cation was prepared by electrospray ionization. The reactants included aliphatic alcohols, phenol and phenyl halides and the reaction studies showed the unique reactivity the of phenoxathiin radical cation towards neutral organic compounds in ambient conditions, which has not been revealed in previous studies.

Antifungal activity of tri- and tetra-thioureido amino derivatives against different Candida species

The in vitro antifungal activity of six thioureido substituted amines (P1-P6) was evaluated against Candida species, including Candida albicans, C. glabrata, C. krusei and C. parapsilosis. These tri- and tetra-thioureido amino derivatives with different methylation levels were synthesised through easy synthetic routes to evaluate their antifungal properties against Candida species. Among all studied derivatives, the tri-(2-thioureido-ethyl)-amine (P1) was the most active compound inhibiting C. albicans and C. glabrata at a concentration of 0.49 μg ml(-1); P3, the N,N',N'',N'''-hexamethyl-derivative, also showed inhibitory activity against C. albicans and C. glabrata, but in higher concentrations (250 μg ml(-1) ). The N,N',N'',N'''-tetramethylated amine (P5) only inhibited the growth of C. glabrata, but its corresponding N,N',N'',N'''-octamethyl derivative (P6) was also active against C. glabrata (125 μg ml(-1)) and it was the only compound active against C. parapsilosis. P2 and P4 showed no significant antifungal activity. The structure-activity relationship of the thioureido-substituted derivatives indicates that the molecular branching and the alkylation levels can influence the antifungal activity. This study demonstrated that thioureido derivatives exhibited significant antifungal activity against Candida species and that they can be considered as a very promising bioactive lead compound to develop novel antifungal agents.

Antifungal activity of Ag(I) and Zn(II) complexes of aminobenzolamide (5-sulfanilylamido-1,3,4-thiadiazole-2-sulfonamide) derivatives

Aminobenzolamide (5-sulfanilylamido-1,3,4-thiadiazole-2-sulfonamide) is a potent inhibitor of the zinc enzyme carbonic anhydrase (CA, EC 4.2.1.1), being at the same time structurally similar to the antimicrobial sulfonamides. Here we report that the reaction of aminobenzolamide with arylsulfonyl isocyanates affords a series of new arylsulfonylureido derivatives which were subsequently used as ligands (in the form of conjugate bases, as sulfonamide anions) for the preparation of metal complexes containing Ag(I) and Zn(II). All the new compounds proved to be very potent inhibitors of CA (isozymes I, II and IV). The newly synthesized complexes, unlike the free ligands, also act as effective antifungal agents against several Aspergillus and Candida spp., some of them showing activities comparable to ketoconazole, with minimum inhibitory concentrations in the range of 1.8-5 microg/mL. The mechanism of antifungal action of these complexes seem to be unconnected with inhibition of lanosterol-14-alpha-demethylase, since the levels of sterols assessed in the fungi cultures were equal in the absence or in the presence of the tested compounds. Probably the new complexes act as inhibitors of phosphomannose isomerase, a key enzyme in the biosynthesis of yeast cell walls.

The antifungal activity of sulfonylated/carboxylated derivatives of dibenzo-1,4-dioxine-2-acetyloxime may be due to inhibition of lanosterol-14alpha-demethylase

Aryl/alkyl-sulfonyl-, aryl/alkylcarboxyl- and aryl(sulfonyl)carbamyl/thiocarbamyl-derivatives of dibenzo-1,4-dioxine-2-acetyloxime were prepared by reaction of the title compound with sulfonyl halides, sulfonic acid anhydrides, acyl chlorides/carboxylic acids, arylsulfonyl isocyanates, aryl/acyl isocyanates or isothiocyanates. Several of the newly synthesized compounds showed effective in vitro antifungal activity against Aspergillus and Candida spp., some of them showing activities comparable to ketoconazole (with minimum inhibitory concentrations in the range of 1.2-4 microg/mL) against the two Aspergillus strains, but possessing a lower activity as compared to ketoconazole against C. albicans. Of the three investigated strains, best activity was detected against A. flavus. The mechanism of action of these compounds probably involves inhibition of ergosterol biosynthesis by interaction with lanosterol-14-alpha-demethylase (CYP51A1), since reduced amounts of ergosterol were found by means of HPLC, in cultures of the sensitive strain A. flavus treated with some of these inhibitors. Thus, the compounds reported here might possess a similar mechanism of action at molecular level with that of the widely used azole antifungals.

Antifungal activity of silver and zinc complexes of sulfadrug derivatives incorporating arylsulfonylureido moieties

Two well known antimicrobial sulfonamides, sulfadiazine and sulfamerazine were reacted with arylsulfonyl isocyanates, affording several new arylsulfonylureido derivatives. These compounds were subsequently used as ligands (in the form of conjugate bases, as sulfonamide anions) for the preparation of metal complexes containing silver and zinc. The newly synthesized complexes, unlike the free ligands, proved to act as effective antifungal agents against several Aspergillus and Candida spp., some of them showing activities comparable to ketoconazole, with minimum inhibitory concentrations in the range of 1.5-5 microg/ml. The mechanism of antifungal action of these complexes seems to be different from that of the azole antifungals acting as lanosterol-14-alpha-demethylase inhibitors. Levels of sterols assayed in the fungi cultures treated with these new antifungals were equal in the absence or in the presence of the tested compounds. This is in strong contrast with similar experiments in which ketoconazole has been used as antifungal, when drastically reduced ergosterol amounts could be detected. Thus, it is probable that the inhibition of phosphomannose isomerase, a key enzyme in the biosynthesis of yeast cell walls, imparts antifungal activity to the new metal complexes reported here.