Synthesis of methyl derivatives of linear and angular thienocoumarins and thiopyranocoumarins

Modular and Regioselective Synthesis of Benzo-Fused Five-Membered Rings Enabled by Co/Ti Synergism

The regiocontrol in constructing benzo-fused five-membered rings by C-H cyclization remains an important challenge. We report a highly general and regioselective methodology to access such heterocycles and indenones, where under the catalysis of CoBr2/bipyridine, aryl titanates, alkynes and EX2 (E = NR, S(O), RP(O), R2Si, CO, etc.) were assembled to various heterocycles and indenones in a modular manner. Unprecedented 1,2-Co/Ti heterobimetallic arylene and benzotitanole intermediates have played crucial roles in these syntheses.

Insight on Mercapto-Coumarins: Synthesis and Reactivity

Mercapto (or sulfanyl)-coumarins are heterocycles of great interest in the development of valuable active structures in material and biological domains. They represent a highly exploitable class of compounds that open many possibilities for further chemical transformations. The present review aims to draw focus toward the synthetic applicability of various forms of mercapto-coumarins and their representations in pharmaceuticals and industries. This work covers the literature issued from 1970 to 2021.

From Propargylic Alcohols to Substituted Thiochromenes: gem-Disubstituent Effect in Intramolecular Alkyne Iodo/hydroarylation

This work describes the 6-endo-dig cyclization of S-aryl propargyl sulfides to afford 2H-thiochromenes. The substitution at the propargylic position plays a crucial role in allowing intramolecular silver-catalyzed alkyne hydroarylation and N-iodosuccinimide-promoted iodoarylation. Additionally, a PTSA-catalyzed thiolation reaction of propargylic alcohols was developed to synthesize the required tertiary S-aryl propargyl ethers. The applicability of merging these two methods is demonstrated by synthesizing the retinoic acid receptor antagonist AGN194310.

Thienochromene derivatives inhibit pSTAT1 and pSTAT5 signaling induced by cytokines

Furanocoumarins, particularly furo[3,2-c]coumarins, are found in many natural products. However, coumarins annulated to a thiophene ring have received scarce attention to date in the literature. Therefore, we synthesized 4-oxo-4H-thieno[3,2-c]chromene derivatives and tested in vitro their anti-inflammatory activity. Anti-inflammatory potential of the synthesized compounds (1, 2, 6-8, 9a-e and 10a-c) has been evaluated by measuring various pSTAT (signal transducer and activator of transcription) inhibition within the JAK (Janus-activated family kinase)/STAT signaling pathway. Ethyl 7-hydroxy-4-oxo-4H-thieno[3,2-c]chromene-2-carboxylate (7) showed best inhibition properties on pSTAT5 in GM-CSF (Granulocyte-macrophage colony-stimulating factor)-triggered PBMC assay, with IC₅₀ value of 5.0 µM.

Differential Effects of Angelicin Analogues on NF-κB Activity and IL-8 Gene Expression in Cystic Fibrosis IB3-1 Cells

The angelicin analogue 4,6,4′-trimethylangelicin (TMA) was recently reported as a strong inhibitor of nuclear factor-κB (NF-κB) activity and of the expression of the interleukin-8 (IL-8) gene in bronchial epithelial cells in which the inflammatory response has been challenged with P. aeruginosa, the most common bacterium found in the airways of patients affected by cystic fibrosis (CF). These findings encouraged us to analyze new synthetic analogues of TMA in order to evaluate their biological activities on human bronchial epithelial CF IB3-1 cells and to find more potent anti-NF-κB agents exhibiting only minor antiproliferative effects. Analogues able to inhibit NF-κB/DNA interaction at lower concentration than TMA were found and selected to investigate their biological activity on IB3-1 cells induced with TNF-α. In this biological system, NF-κB-mediated IL-8 gene expression was investigated. Some analogues showed similar activity to the lead compound TMA. Other analogues displayed higher activities; in particular, the most interesting compounds showing relevant anti-inflammatory effects were found to cause 56–83% reduction of IL-8 mRNA expression at low concentrations (1–10 μM), without changes in cell proliferation pattern, demonstrating their potential interest for a possible development of anti-inflammatory therapy of cystic fibrosis.

1-Thioangelicin: crystal structure, computer-aided studies and photobiological activity

1-Thioangelicin is a furocoumarin analog synthesized to investigate the role of the substitution of sulfur for oxygen in the parent compound angelicin. The compound was examined by X-ray diffraction, and its interaction with DNA, both in the dark and by UVA irradiation, studied by means of linear flow dichroism, chromatography and (1)H NMR. Further insight into the steric and electronic features of 1-thioangelicin has been reached through theoretical calculations, including molecular mechanics optimization, docking studies and frontier molecular orbital investigations. The experimental data indicate that thioangelicin is able to intercalate in the DNA helix and subsequent irradiation yields a cis-syn adduct, in agreement with theoretical calculations within the lower/higher singly occupied molecular orbital formalism. Antiproliferative activity has been assessed on Balb/c 3T3 cultured cells.

Highly potent inhibitors of TNF-alpha production. Part I: discovery of new chemical leads and their structure-activity relationships

Discovery of new chemical leads of inhibitors for TNF-alpha production starting from the chemical modification of 1 is reported. Further biological studies of 1 to disclose the site of its action strongly suggested that 1 inhibits LPS-induced TNF-alpha expression in the liver and spleen of mice. Structure-activity relationships (SARs) are also discussed and full details including the chemistry are reported.

Novel angular furo and thieno-quinolinones: synthesis and preliminary photobiological studies

A number of new furo and thienoquinolinones carrying an electron-withdrawing function or unsubstituted at the position 3 were synthesized in order to obtain new potential photochemotherapeutic agents with increased antiproliferative activity and decreased toxic side effects. Our interest in studying the SAR of these derivatives also prompted us to investigate the influence of N-methylation on biological activity, by preparing N-methyl derivatives. The antiproliferative activity of all the newly synthesized compounds was evaluated and compared to 8-methoxypsoralen (8-MOP), the drug widely used in PUVA-therapy. The 3-unsubstituted thienoquinolinones were generally the most potent derivatives, followed by the furo-analogues. In particular, the unsubstituted thieno[2,3-h]quinoline-2(1H)one showed the highest activity in T2 bacteriophage, HeLa cells and Ehrlich cells tests. All the compounds, assayed on Escherichia coli WP2 TM9, showed a similar mutagenic activity, very close to that of 8-MOP. Except for 2-oxo-1,2-dihydrothieno[2,3-h]quinoline-3-carboxylic acid, which appeared to be very effective, all compounds generated singlet oxygen to slightly larger amounts when compared to 8-MOP. The N-methyl analogues only induced moderate skin erythemas on albino guinea pigs, while all other derivatives appeared to be entirely inactive. On the basis of these results, the unsubstituted thieno[2,3h]quinoline 2(1H)one seems to be the most interesting potential drug for PUVA photochemotherapy and photopheresis.

Reversed‐phase high‐performance liquid chromatography (RP‐HPLC) determination of lipophilicity of furocoumarins: Relationship with DNA interaction

The partition coefficient (P) of 82 furocoumarins and analogs (psoralens, angelicins, allopsoralens, 8-azapsoralens, angular furoquinolin-2-ones, sulfur and selenium isosters of psoralen and angelicin) has been determined by reversed-phase HPLC. The chromatographic behavior correlates well with the in vitro affinity of the compounds toward DNA.

Photochemical and photobiological studies on methylthioangelicins

4,4',5'-Trimethyl-1'-thioangelicin (1) and 4,6,4',5'-tetramethyl-1'-thioangelicin (2), two newly synthesised isosters of furocoumarins having a sulfur atom in their five-membered ring, were studied in terms of interactions with DNA, both in the ground state and after UVA light absorption. The compounds were able to intercalate the macromolecule and to photobind efficiently, forming C4-cycloadducts with thymine. The antiproliferative effect of this binding was shown in Ehrlich and HeLa cells and by T2 phage inactivation. Tests on Salmonella typhimurium indicated low mutagenic activity. In particular, compound 1 has photobiological activity comparable with that of 4,6,4'-trimethylangelicin, but is less mutagenic.

Synthesis and biological activity of linear and angular 4-methoxymethylthienocoumarins and 4-acetoxymethylthienocoumarins

This paper reports the synthesis of 4-methoxymethyl and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[3,2-g]-1-benzopyran-2-one as well as 4-methoxymethyl- and 4-acetoxymethyl-6,9-dimethyl-2H-thieno[2,3-h]-1- benzopyran-2-one. The synthesized derivatives were tested on human cells in UVA irradiation conditions. Skin phototoxicity and cross-link formation in DNA were also studied. Results indicate that the new thienocoumarins have good antiproliferative activity, greater than that of the well-known photochemotherapeutic drug 8-methoxypsoralen, but they are practically devoid of skin photosensitization effects.