Catalytic Enantioselective Allyl–Allyl Cross-Coupling with a Borylated Allylboronate

Catalytic enantioselective allyl–allyl cross-coupling of a borylated allylboronate reagent gives versatile borylated chiral 1,5-hexadienes. These compounds may be manipulated in a number of useful ways to give functionalized chiral building blocks for asymmetric synthesis

Selectivity Determination of a Small Molecule Chemical Probe Using Protein Microarray and Affinity Capture Techniques

Small molecule selectivity is an essential component of candidate drug selection and target validation. New technologies are required to better understand off-target effects, with particular emphasis needed on broad protein profiling. Here, we describe the use of a tritiated chemical probe and a 9000 human protein microarray to discern the binding selectivity of an inhibitor of the mRNA decapping scavenger enzyme DcpS. An immobilized m⁷GTP resin was also used to assess the selectivity of a DcpS inhibitor against mRNA cap-associated proteins in whole cell extracts. These studies confirm the exquisite selectivity of diaminoquinazoline DcpS inhibitors, and highlight the utility of relatively simple protein microarray and affinity enrichment technologies in drug discovery and chemical biology

Covalent Enzyme Inhibition through Fluorosulfate Modification of a Noncatalytic Serine Residue

Irreversible enzyme inhibitors and covalent chemical biology probes often utilize the reaction of a protein cysteine residue with an appropriately positioned electrophile (<i>e.g.</i>, acrylamide) on the ligand template. However, cysteine residues are not always available for site-specific protein labeling, and therefore new approaches are needed to expand the toolkit of appropriate electrophiles (“warheads”) that target alternative amino acids. We previously described the rational targeting of tyrosine residues in the active site of a protein (the mRNA decapping scavenger enzyme, DcpS) using inhibitors armed with a sulfonyl fluoride electrophile. These inhibitors subsequently enabled the development of clickable probe technology to measure drug-target occupancy in live cells. Here we describe a fluorosulfate-containing inhibitor (aryl fluorosulfate probe (FS-p1)) with excellent chemical and metabolic stability that reacts selectively with a noncatalytic serine residue in the same active site of DcpS as confirmed by peptide mapping experiments. Our results suggest that noncatalytic serine targeting using fluorosulfate electrophilic warheads could be a suitable strategy for the development of covalent inhibitor drugs and chemical probes

Design of Potent mRNA Decapping Scavenger Enzyme (DcpS) Inhibitors with Improved Physicochemical Properties To Investigate the Mechanism of Therapeutic Benefit in Spinal Muscular Atrophy (SMA)

The C-5 substituted 2,4-diaminoquinazoline RG3039 (compound <b>1</b>), a member of a chemical series that was identified and optimized using an SMN2 promoter screen, prolongs survival and improves motor function in a mouse model of spinal muscular atrophy (SMA). It is a potent inhibitor of the mRNA decapping scavenger enzyme (DcpS), but the mechanism whereby DcpS inhibition leads to therapeutic benefit is unclear. Compound <b>1</b> is a dibasic lipophilic molecule that is predicted to accumulate in lysosomes. To understand if the <i>in vivo</i> efficacy is due to DcpS inhibition or other effects resulting from the physicochemical properties of the chemotype, we undertook structure based molecular design to identify DcpS inhibitors with improved physicochemical properties. Herein we describe the design, synthesis, and <i>in vitro</i> pharmacological characterization of these DcpS inhibitors along with the <i>in vivo</i> mouse CNS PK profile of PF-DcpSi (compound <b>24</b>), one of the analogs found to be efficacious in SMA mouse model