Microwave-Assisted Synthesis of Aminophosphonic Derivatives and Their Antifungal Evaluation against Lomentospora prolificans

Lomentospora prolificans is a pathogenic and multidrug-resistant fungus that can infect both immunocompetent and immunocompromised patients, with mortality rates up to 87%. The World Health Organization (WHO) included this fungal species in its first list of 19 priority fungal pathogens, which focused on fungal pathogens that can cause invasive acute and subacute systemic fungal infections. Therefore, there is a growing interest in finding new therapeutic alternatives. In this work, the synthesis of twelve α-aminophosphonates by the microwave-assisted Kabachnik-Fields reaction and twelve α-aminophosphonic acids by a monohydrolysis reaction is reported. All compounds were evaluated by the agar diffusion method as a preliminary screening in comparison with voriconazole, showing inhibition halos for compounds 7, 11, 13, 22 and 27. The five active compounds in the preliminary tests were evaluated against five strains of L. prolificans following protocol M38-A2 from CLSI. The results showed that these compounds exhibit antifungal activity in the concentration range of 900->900 μg/mL. Cytotoxicity against healthy COS-7 cells was also evaluated by the MTT assay, and it was shown that compound 22 was the least cytotoxic, with a viability of 67.91%, comparable to the viability exhibited by voriconazole (68.55%). Docking studies showed that the possible mechanism of action of the active compounds could be through the inhibition of the enzyme lanosterol-14-alpha-demethylase in an allosteric hydrophobic cavity.

Synthesis of α-Aminophosphonates and Related Derivatives; the Last Decade of the Kabachnik-Fields Reaction

The Kabachnik-Fields reaction, comprising the condensation of an amine, oxo compound and a P-reagent (generally a >P(O)H species or trialkyl phosphite), still attracts interest due to the challenging synthetic procedures and the potential biological activity of the resulting α-aminophosphonic derivatives. Following the success of the first part (Molecules 2012, 17, 12821), here we summarize the synthetic developments in this field accumulated in the last decade. The procedures compiled include catalytic accomplishments as well as catalyst-free and/or solvent-free "greener" protocols. The products embrace α-aminophosphonates, α-aminophosphinates, and α-aminophosphine oxides along with different bis derivatives from the double phospha-Mannich approach. The newer developments of the aza-Pudovik reactions are also included.

Microwaves as "Co-Catalysts" or as Substitute for Catalysts in Organophosphorus Chemistry

The purpose of this review is to summarize the importance of microwave (MW) irradiation as a kind of catalyst in organophosphorus chemistry. Slow or reluctant reactions, such as the Diels-Alder cycloaddition or an inverse-Wittig type reaction, may be performed efficiently under MW irradiation. The direct esterification of phosphinic and phosphonic acids, which is practically impossible on conventional heating, may be realized under MW conditions. Ionic liquid additives may promote further esterifications. The opposite reaction, the hydrolysis of P-esters, has also relevance among the MW-assisted transformations. A typical case is when the catalysts are substituted by MWs, which is exemplified by the reduction of phosphine oxides, and by the Kabachnik-Fields condensation affording α-aminophosphonic derivatives. Finally, the Hirao P-C coupling reaction may serve as an example, when the catalyst may be simplified under MW conditions. All of the examples discussed fulfill the expectations of green chemistry.

Microwave irradiation and catalysis in organophosphorus reactions

The usual advantage of microwave (MW) assistance is making organic reactions faster and more efficient. In this article we present reaction types from organophosphorus chemistry, when MW-assisted transformations (e.g. the direct esterification and alkylating esterification of phosphinic acids) may be promoted by suitable catalysts, or vice versa, when a catalytic reaction is enhanced by MW irradiation (e.g. the Arbuzov reaction of aryl halides), and when catalysts may be omitted or simplified under MW irradiation as shown by the alkylation of active methylene containing P=O substrates/the Kabachnik–Fields reaction/deoxygenation of phosphine oxides, and the Hirao reaction, respectively.

Molecular docking, molecular modeling, vibrational and biological studies of some new heterocyclic α-aminophosphonates

A new diphenyl (aryl) (Ǹ-quinazolin-4-yl-hydrazino) methylphosphonates 3a-3d was synthesized via anhydrous zinc chloride catalyzed Kabachnic-Fields reaction. The structure of the synthesized compounds was confirmed by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, ³¹P NMR and MS spectral data. The synthesized compounds showed significant antimicrobial and also remarkable cytotoxicity anticancer activities against breast carcinoma cell line (MCF7). The quantum chemical calculations were performed using density functional theory (DFT) to study the effect of the changes of molecular and electronic structures on the biological activity of the investigated compounds. Also, NBO and theoretical FT-IR were calculated. The experimental results were validated by molecular docking simulation of compound 3b in the active pocket of the enzyme. The important binding interactions with the key residues in the active site were revealed. A good correlation was found between the quantum chemical parameters and experimental data.

Marrying multicomponent reactions and aggregation-induced emission (AIE): new directions for fluorescent nanoprobes

Recent development and progress for fabrication and applications of aggregation-induced emission polymers through multicomponent reactions have been summarized in this review.

2-[Anilino(diphenylphosphoryl)methyl]phenol from a three-component Kabachnik-Fields reaction

The title compound, C25H22NO2P, was synthesized in high yield by a three-component Kabachnik-Fields reaction of diphenylphosphine oxide, salicylaldehyde and aniline in dry toluene at room temperature. It precipitates as racemic crystals, in which strong hydrogen bonds between the hydroxy group and the P=O group of a neighbouring molecule form one-dimensional heterochiral chains along the crystallographic a axis, with an O···O separation of 2.568 (2) Å. The pseudo-tetrahedral environment of the P atom is distorted, with O-P-C bond angles significantly larger than the C-P-C angles.