Chemoselective Amide Formation Using O-(4-Nitrophenyl)hydroxylamines and Pyruvic Acid Derivatives

Efficient solvent- and temperature-tuned access to aldoxime ethers and phenolic functions by Pd-catalyzed C–O cross-coupling of aldoximes with aryl bromides and bromo-chalcones

A single method with a functionality switching option, to access oxime ethers and phenols, was developed for the first time for the Pd-catalyzed C–O cross-coupling of aryl bromides and bromo-chalcones with aldoximes.

RNAi-mediated TCF-3 gene silencing inhibits proliferation of Eca-109 esophageal cancer cells by inducing apoptosis

Esophageal cancer (EC) remains an important health problem in China. In the present study, through the use of siRNA, specific gene knockdown of transcription factor 3 gene (TCF-3) was achieved in vitro and the effect of TCF-3 gene on human EC Eca-109 cell proliferation and apoptosis. Eca-109 cells were treated using negative control (NC) of siRNA against TCF-3 (siTCF-3) and siTCF-3 group. Colony formation assay was used to detect the colony formation ability in Eca-109 cells. MTT assay was used to measure the cell growth and viability, whereas BrDU assay was used to evaluate cell proliferation, and flow cytometry (FCM) to assess cell apoptosis. Reverse-transcription quantitative PCR (RT-qPCR) was applied to measure TCF-3 gene expression. Protein expressions of TCF-3, apoptosis-related proteins, Bcl-2, Bax, and caspase-3 were determined using Western blotting. Transfection of siTCF-3 successfully down-regulated TCF-3 gene expression. In addition, siTCF-3, reduced Eca-109 cell viability and proliferation, in a time-dependent manner, and inhibited progression of cell cycle from G₀/G₁ to S-stage. When treated with siTCF-3, the Eca-109 cells exhibited increased apoptosis, with up-regulated cleaved caspase and Bax expressions, whereas Bcl-2 expression was down-regulated. The present study shows that TCF-3 gene silencing inhibits Eca-109 cell growth and proliferation, suppresses cell cycle progression, and promotes apoptosis, which might serve as a new objective for EC treatment.

Synthesis and chemoselective ligations of MIDA acylboronates with O-Me hydroxylamines

A chemoselective amide-bond forming ligation of N-methyliminodiacetyl (MIDA) acylboronates and O-Me hydroxylamines, including unprotected peptide substrates, is described.

Chemical Protein Synthesis with the KAHA Ligation

Since the first report of the chemoselective amide bond forming reaction between α-ketoacids and hydroxylamines in 2006, the KAHA (α-ketoacid-hydroxylamine) ligation has advanced to a useful tool for the routine synthesis of small to medium sized proteins and cyclic peptides. In this chapter we introduce the concept of KAHA ligation starting with the synthesis and properties of hydroxylamines and α-ketoacids, methods for their incorporation into peptides, and give an insight into the mechanism of the KAHA ligation. We cover important improvements including sequential ligations with 5-oxaproline, traceless synthesis of peptide α-ketoacids and show their application in chemical protein synthesis and cyclic peptide synthesis. Recent developments of the KAT (potassium acyl trifluoroborate) ligation and its application as fast and chemoselective bioconjugation method are described and an outlook on ongoing work and possible future developments is given at the end of the chapter.