Synthesis of Highly Substituted Imidazolidine-2,4-dione (Hydantoin) through Tf₂O‑Mediated Dual Activation of Boc-Protected Dipeptidyl Compounds

Highly substituted chiral hydantoins were readily synthesized from simple dipeptides in a single step under mild conditions. This reaction proceeded through the dual activation of an amide and a <i>tert</i>-butyloxycarbonyl (Boc) protecting group by Tf₂O-pyridine. This method was successfully applied in the preparation of a variety of biologically active compounds, including drug analogs and natural products

Development of a Selective Labeling Probe for Bruton’s Tyrosine Kinase Quantification in Live Cells

As a key regulator of the B-cell receptor signaling pathway, Bruton’s tyrosine kinase (Btk) has emerged as an important therapeutic target for various malignancies and autoimmune disorders. However, data on the expression profiles of Btk are lacking. Here, we report the discovery of a new, selective Btk probe and of a sandwich-type ELISA quantification method to detect endogenous Btk in live cells. We achieved selective labeling of Btk in vivo and quantified Btk levels in seven types of human lymphoma cell lines. This quantification method provides a powerful tool to study Btk in live cells that may also be useful in clinical settings

Site-Selective Protein Immobilization by Covalent Modification of GST Fusion Proteins

The immobilization of functional proteins onto solid supports using affinity tags is an attractive approach in recent development of protein microarray technologies. Among the commonly used fusion protein tags, glutathione <i>S</i>-transferase (GST) proteins have been indispensable tools for protein–protein interaction studies and have extensive applications in recombinant protein purification and reversible protein immobilization. Here, by utilizing pyrimidine-based small-molecule probes with a sulfonyl fluoride reactive group, we report a novel and general approach for site-selective immobilization of Schistosoma japonicum GST (<i>sj</i>GST) fusion proteins through irreversible and specific covalent modification of the tyrosine-111 residue of the <i>sj</i>GST tag. As demonstrated by <i>sj</i>GST-tagged eGFP and <i>sj</i>GST-tagged kinase activity assays, this immobilization approach offers the advantages of high immobilization efficiency and excellent retention of protein structure and activity

Discovery of a Series of 2,5-Diaminopyrimidine Covalent Irreversible Inhibitors of Bruton’s Tyrosine Kinase with in Vivo Antitumor Activity

Bruton’s tyrosine kinase (Btk) is an attractive drug target for treating several B-cell lineage cancers. Ibrutinib is a first-in-class covalent irreversible Btk inhibitor and has demonstrated impressive effects in multiple clinical trials. Herein, we present a series of novel 2,5-diaminopyrimidine covalent irreversible inhibitors of Btk. Compared with ibrutinib, these inhibitors exhibited a different selectivity profile for the analyzed kinases as well as a dual-action mode of inhibition of both Btk activation and catalytic activity, which counteracts a negative regulation loop for Btk. Two compounds from this series, <b>31</b> and <b>38</b>, showed potent antiproliferative activities toward multiple B-cell lymphoma cell lines, including germinal center B-cell-like diffuse large B cell lymphoma (GCB-DLBCL) cells. In addition, compound <b>31</b> significantly prevented tumor growth in a mouse xenograft model