Investigations of the Thermal Responsiveness of 1,4,2-Oxathiazoles

FETPY: a Diiron(I) Thio-Carbyne Complex with Prominent Anticancer Activity In Vitro and In Vivo

FETPY, an organo-diiron(I) complex, showed strong cytotoxicity across a panel of human and mouse cancer cell lines, combined with an outstanding selectivity compared to nonmalignant cells. Enhanced iron uptake in aggressive, low-differentiated cell lines, caused membrane lipid peroxidation, which resulted in ferroptosis in human ovarian cancer cells. FETPY induced significant morphological changes in murine B16-F1 and B16-F10 melanoma cells, leading to senescence and/or trans-differentiation into Schwann-like cells, thus significantly reducing their tumorigenic potential. Additionally, FETPY substantially suppressed tumor growth in low- and high-grade syngeneic melanoma models when administered in a therapeutic regimen. FETPY is featured by satisfactory water solubility (millimolar range), an amphiphilic character (Log Pow = -0.17), and excellent stability in a biological medium (DMEM). These important requisites for drug development are rarely met in iron complexes investigated so far as possible anticancer agents. Overall, FETPY holds promise as a safe and potent targeted antitumor agent.

[4+2]-Cycloaddition to 5-Methylidene-Hydantoins and 5-Methylidene-2-Thiohydantoins in the Synthesis of Spiro-2-Chalcogenimidazolones

Novel hydantion and thiohydantoin-based spiro-compounds were prepared via theDiels-Alder reactions between 5-methylidene-hydantoins or 5-methylidene-2-thiohydantoins and 1,3-dienes (cyclopentadiene, cyclohexadiene, 2,3-dimethylbutadiene, isoprene). It was shown that the cycloaddition reactions proceed regioselectively and stereoselectively with the formation of exo-isomers in the reactions with cyclic dienes andthe less sterically hindered products in the reactions with isoprene. Reactions of methylideneimidazolones with cyclopentadiene proceed viaco-heating the reactants; reactions with cyclohexadiene, 2,3-dimethylbutadiene, and isoprene require catalysis by Lewis acids. It was demonstrated that ZnI₂ is an effective catalyst in the Diels-Alder reactions of methylidenethiohydantoins with non-activated dienes. The possibility of alkylation and acylation of the obtained spiro-hydantoinsat the N(1)nitrogen atoms with PhCH₂Cl or Boc₂O and the alkylation of the spiro-thiohydantoinsat the S atoms with MeI or PhCH₂Cl in high yields have been demonstrated. The preparativetransformation of spiro-thiohydantoins into corresponding spiro-hydantoinsin mild conditions by treating with 35% aqueous H₂O₂ or nitrile oxide has been carried out. The obtained compounds show moderate cytotoxicity in the MTT test on MCF7, A549, HEK293T, and VA13 cell lines. Some of the tested compounds demonstrated some antibacterial effect against Escherichia coli (E. coli) BW25113 DTC-pDualrep2 but were almost inactive against E. coli BW25113 LPTD-pDualrep2.

Polythionoester Vesicle: An Efficient Polymeric Platform for Tuning H2S Release

Hydrogen sulfide (H₂S) serves as a key gaseous regulator that not only directs many physiological activities, but also manifests therapeutic benefits to many diseases. Developing H₂S vehicle platforms for its local delivery and long-acting release is important to achieve target gas therapy. Most of the known H₂S-donating polymers contain labile thioester scaffolds within their structures that suffer from the issue of low gas releasing efficiency. Here we present the use of thionoester, a constitutional isomer of thioester, as the functional unit to build a structural platform of cysteine-triggered H₂S donor polymer, polythionoester. Simple exchange of the sulfur and oxygen positions in the carbonyl sulfide scaffold makes the polythionoesters undergo a distinct mechanism of H₂S production, which can largely improve the gas-releasing efficiency (>80%). Moreover, the thionoester-containing block copolymers can self-assemble into vesicles in an aqueous media. We discover that control over the size effect can adjust the vesicle disassembly rate and gas-releasing kinetics. A tunable half-life of H₂S generation (2.6-9.8 h) can be accessed by tailoring the vesicle dimension. This allows such polymersomes to be potential as a gas nanodelivery system for long-lasting gas therapeutics.

An Approach to Vinylidenequinazolines from Isoxazoles and Dioxazolones

An effective strategy for the synthesis of vinylidenequinazolines has been efficaciously developed, which involves Rh(III)-assisted C-H amidation followed by ring-opening and intramolecular annulation. This protocol shows a straightforward way to construct diverse quinazoline units with a wide functional group compatibility from readily available isoxazoles and dioxazolones.

An Efficient and Straightforward Approach for Accessing Thioesters via Palladium-Catalyzed C-N Cleavage of Thioamides

We first report the coupling of activated thioamides with alcohols to efficiently form thioesters via palladium-catalyzed C-N cleavage strategy. The new approach employs the thioamides as thioacylating reagent to give...

Thiobenzophenones: tunable hydrolysis-based donors for intracellular H2S delivery

H2S, the third gasotransmitter, is involved in many physiological and pathological processes. Compounds that can release H2S slowly under physiological conditions are useful chemical tools for studying H2S biology as...

Base-Catalyzed Transesterification of Thionoesters

Here we report a convenient synthesis of thionoesters by base-catalyzed transesterification. Benzyl and alkyl thionobenzoates and thionoheterobenzoates were efficiently prepared using various alcohols catalyzed by the corresponding sodium alkoxide. This methodology features a broad substrate scope, good to excellent yields, short reaction times, while simultaneously driving the reaction toward completion through the removal of the methanol byproduct. We also report the conversion of a small collection of thionobenzoates into the corresponding α,α-difluorobenzyl ethers to demonstrate the conversion of alcohols into difluorobenzyl or difluoroheterobenzyl ethers, a process that could prove useful for lead optimization in medicinal chemistry.

Thionoesters: A Native Chemical Ligation-Inspired Approach to Cysteine-Triggered H2S Donors

Native chemical ligation (NCL) is a simple, widely used, and powerful synthetic tool to ligate N-terminal cysteine residues and C-terminal α-thioesters via a thermodynamically stable amide bond. Building on this well-established reactivity, as well as advancing our interests in the chemical biology of reactive sulfur species including hydrogen sulfide (H₂S), we hypothesized that thionoesters, which are constitutional isomers of thioesters, would undergo a similar NCL reaction in the presence of cysteine to release H₂S under physiological conditions. Herein, we report mechanistic and kinetic investigations into cysteine-mediated H₂S release from thionoesters. We found that this reaction proceeds with high H₂S-releasing efficiency (∼80%) and with a rate constant (9.1 ± 0.3 M^-1 s^-1) comparable to that for copper-catalyzed azide-alkyne cycloadditions (CuAAC). Additionally, we found that the final product of the reaction of cysteine with thionoesters results in the formation of a stable dihydrothiazole, which is an iron-binding motif commonly found in siderophores produced by bacteria during periods of nutrient deprivation.