Microwave acceleration in DABAL-Me3-mediated amide formation

Bicyclic enol cyclocarbamates inhibit penicillin-binding proteins

Natural products form attractive leads for the development of chemical probes and drugs. The antibacterial lipopeptide Brabantamide A contains an unusual enol cyclocarbamate and we used this scaffold as inspiration for the synthesis of a panel of enol cyclocarbamate containing compounds. By equipping the scaffold with different groups, we identified structural features that are essential for antibacterial activity. Some of the derivatives block incorporation of hydroxycoumarin carboxylic acid-amino d-alanine into the newly synthesized peptidoglycan. Activity-based protein-profiling experiments revealed that the enol carbamates inhibit a specific subset of penicillin-binding proteins in B. subtilis and S. pneumoniae.

Bimetallic Cobalt-Rhodium Nanoparticle-Catalyzed Reductive Amination of Aldehydes with Nitroarenes Under Atmospheric Hydrogen

A cobalt-rhodium heterobimetallic nanoparticle (Co₂Rh₂/C)-catalyzed tandem reductive amination of aldehydes with nitroaromatics to sec-amines has been developed. The tandem reaction proceeds without any additives under mild conditions (1 atm H₂ and 25 °C). This procedure can be scaled up to the gram scale, and the catalyst can be reused more than six times without loss of activity.

Chemoproteomics-Aided Medicinal Chemistry for the Discovery of EPHA2 Inhibitors

The receptor tyrosine kinase EPHA2 has gained attention as a therapeutic drug target for cancer and infectious diseases. However, EPHA2 research and EPHA2-based therapies have been hampered by the lack of selective small-molecule inhibitors. Herein we report the synthesis and evaluation of dedicated EPHA2 inhibitors based on the clinical BCR-ABL/SRC inhibitor dasatinib as a lead structure. We designed hybrid structures of dasatinib and the previously known EPHA2 binders CHEMBL249097, PD-173955, and a known EPHB4 inhibitor in order to exploit both the ATP pocket entrance as well as the ribose pocket as binding epitopes in the kinase EPHA2. Medicinal chemistry and inhibitor design were guided by a chemical proteomics approach, allowing early selectivity profiling of the newly synthesized inhibitor candidates. Concomitant protein crystallography of 17 inhibitor co-crystals delivered detailed insight into the atomic interactions that underlie the structure-affinity relationship. Finally, the anti-proliferative effect of the inhibitor candidates was confirmed in the glioblastoma cell line SF-268. In this work, we thus discovered a novel EPHA2 inhibitor candidate that features an improved selectivity profile while maintaining potency against EPHA2 and anticancer activity in SF-268 cells.

Discovery of Novel 1,4-Diacylpiperazines as Selective and Cell-Active eIF4A3 Inhibitors

Eukaryotic initiation factor 4A3 (eIF4A3), a member of the DEAD-box RNA helicase family, is one of the core components of the exon junction complex (EJC). The EJC is known to be involved in a variety of RNA metabolic processes typified by nonsense-mediated RNA decay (NMD). In order to identify molecular probes to investigate the functions and therapeutic relevance of eIF4A3, a search for selective eIF4A3 inhibitors was conducted. Through the chemical optimization of 1,4-diacylpiperazine derivatives identified via high-throughput screening (HTS), we discovered the first reported selective eIF4A3 inhibitor 53a exhibiting cellular NMD inhibitory activity. A surface plasmon resonance (SPR) biosensing assay ascertained the direct binding of 53a and its analog 52a to eIF4A3 and revealed that the binding occurs at a non-ATP binding site. Compounds 52a and 53a represent novel molecular probes for further study of eIF4A3, the EJC, and NMD.

Palladium supported on hollow magnetic mesoporous spheres: a recoverable catalyst for hydrogenation and Suzuki reaction

Highly efficient and magnetically recoverable HMMS–saplr–Pd(0) was developed for hydrogenation and Suzuki reaction.

Synthesis of phosphaisocoumarin amidates via DIBAL-H-mediated selective amidation of phosphaisocoumarin esters

A series of phosphaisocoumarin amidates were synthesized for the first time via DIBAL-H-mediated direct amidation of phosphaisocoumarin esters under mild conditions in good to excellent yields. The present reaction showed high selectivity. In each case, the phostone ring was intact and only the exocyclic ethoxy group was amidated. A plausible mechanism of the reaction was provided.

Simple Synthesis of Amides and Weinreb Amides via Use of PPh3 or Polymer-Supported PPh3 and Iodine

The combination of PPh₃/I₂ has been shown to be effective for conversion of a range of carboxylic acids to 2°, 3°, and Weinreb amides. Simplification of the procedure was possible with the use of polymer-supported PPh₃/I₂. Weinreb amides produced via the use of polymer-supported PPh₃ could be filtered through a short silica gel plug and used in further transformations. Thus, use of polymer-supported PPh₃ offers potential applicability to diversity-oriented reactions. Formal total syntheses of apocynin and pratosine, as well as syntheses of anhydrolychorinone and hippadine, have been achieved via the use of this amide-forming method. An attempt has been made to gain insight into this reaction.