Synthesis, Molecular Engineering, and Photophysical Properties of Fluorescent Thieno[3,2- b]pyridine-5(4 H)-ones

Synthesis of Spiro[indoline-pyridine]-dicarboxylates and Substituted Alkylidene Oxindoles by Azomethine Ylides and MBH Carbonates of Isatins

We have developed an efficient protocol for the synthesis of spiro[indoline-pyridine]dicarboxylates and substituted alkylidene oxindoles through [3 + 3] cycloaddition and Michael addition individually by azomethine ylides and various MBH carbonates of isatins. The selective generation of cyclic products and chain products was achieved by changing the substituents at the 3-position of the oxindoles. The features of this method include convenient catalysts, mild reaction conditions, and broad substrate scopes.

Gold(I)-Catalyzed Intramolecular Hydrothiophenylation of N-Thiophen-3-yl Alkynylamides for Accessing Thieno[3,2-b]pyridine-5(4H)-ones: Development of F-Actin Specific Fluorescent Probes

Herein, we describe an original synthetic method for a series of fluorescent thieno[3,2-b]pyridine-5(4H)-one derivatives prepared via the gold(I)-catalyzed 6-endo-dig intramolecular hydrothiophenylation process involving N-thiophen-3-yl alkynylamides. The brightness was improved; emission could be tuned, and larger Stokes shifts were recorded. We also designed and synthesized the phalloidin-based fluorescent chemical probes KF-P1 and KF-P2 to realize fluorescent F-actin imaging.

A Fluorescent Probe for Selective Facile Detection of H2S in Serum Based on an Albumin-Binding Fluorophore and Effective Masking Reagent

A fluorescent probe (4-(2-(4-(diethylamino)phenyl)-4-methyl-5-oxo-4,5-dihydrothieno[3,2-b]pyridin-7-yl)phenyl 2,4-dinitrobenzenesulfonate, KF-DNBS) for facile detection of H₂S in serum was developed based on the combination of an environment-sensitive fluorophore (2-(4-(diethylamino)phenyl)-7-(4-hydroxyphenyl)-4-methylthieno[3,2-b]pyridin-5(4H)-one, KF) with albumin and the 2,4-dinitrobenzene sulfonyl (DNBS) group as a recognition unit for H₂S. KF-DNBS showed remarkable fluorescence enhancement due to H₂S-triggered thiolysis followed by the formation of a fluorescent fluorophore (KF)-albumin complex. The H₂S detection limit of KF-DNBS was estimated to be 3.2 μM, and KF-DNBS achieves a high selectivity to H₂S over biothiols by employing 2-formyl benzene boronic acid (2-FBBA) as an effective masking reagent. Furthermore, under optimized sensing conditions, KF-DNBS could be applied to accurately determine spiked H₂S in human serum without the need for any further procedure for the removal of serum proteins.

Domino Synthetic Strategy for Tetrahydrothiopyran Derivatives from Benzaldehydes, 2-Acetylfuran/2-Acetylthiophene, and Sodium Sulfide

A novel domino reaction from benzaldehydes and 2-acetylfuran/2-acetylthiophene with sodium sulfide was developed to synthesize a series of tetrahydrothiopyran (THTP) derivatives. The reaction proceeded well to construct a tetrahydrothiopyran ring and five new bonds in one step. A mechanism is proposed, involving a stepwise Aldol/double Michael addition/Aldol (AMMA) reaction cascade. In this transformation, sodium sulfide acts as a nucleophile and base. This method is characterized by transition-metal-free, commercially available starting materials and mild reaction conditions.

Development of Human Serum Albumin Selective Fluorescent Probe Using Thieno[3,2-b]pyridine-5(4H)-one Fluorophore Derivatives

The level of human serum albumin (HSA) in biological fluids is a key health indicator and its quantitative determination has great clinical importance. In this study, we developed a selective and sensitive fluorescent HSA probe by fluorescence-based high-throughput screening of a set of fluorescent thieno[3,2-b]pyridine-5(4H)-one derivatives against major plasma proteins: HSA, bovine serum albumin (BSA), globulin, fibrinogen, and transferrin. The fluorophore chosen finally (4) showed noticeable fluorescence enhancement in the presence of HSA (160-fold increase), and it exhibited rapid response, high sensitivity (detection limit 8 nM), and the ability to clearly distinguish HSA from BSA in pH 9 buffer condition. Moreover, the probe could be applicable to detect trace amounts of HSA in an artificial urine sample; further, it might be applied to the determination of the HSA concentration in complex biological samples for pre-clinical diagnosis.