Chemical tools and methods that report on G protein-coupled receptor (GPCR) expression levels and receptor occupancy by small molecules are highly desirable. We report the development of LEI121 as a photoreactive probe to study the type 2 cannabinoid receptor (CB2R), a promising GPCR to treat tissue injury and inflammatory diseases. LEI121 is the first CB2R-selective bifunctional probe that covalently captures CB2R upon photoactivation. An incorporated alkyne serves as ligation handle for the introduction of reporter groups. LEI121 enables target engagement studies and visualization of endogenously expressed CB2R in HL-60 as well as primary human immune cells using flow cytometry. Our findings show that strategically functionalized probes allow monitoring of endogenous GPCR expression and engagement in human cells using tandem photoclick chemistry and hold promise as biomarkers in translational drug discovery.

The cannabinoid receptor 1 (CB1) is an inhibitory G protein-coupled receptor abundantly expressed in the central nervous system. It has rich pharmacology and largely accounts for the recreational use of cannabis. We describe efficient asymmetric syntheses of four photoswitchable Δ-tetrahydrocannabinol derivatives (azo-THCs) from a central building block 3-Br-THC. Using electrophysiology and a FRET-based cAMP assay, two compounds are identified as potent CB1 agonists that change their effect upon illumination. As such, azo-THCs enable CB1-mediated optical control of inwardly rectifying potassium channels, as well as adenylyl cyclase.

The tert-butyl group is a common motif in medicinal chemistry. Its incorporation into bioactive compounds is often accompanied by unwanted property modulation, such as increased lipophilicity and decreased metabolic stability. Several alternative substituents are available for the drug discovery process. Herein, physicochemical data of two series of drug analogues of bosentan and vercirnon are documented as part of a comparative study of tert-butyl, pentafluorosulfanyl, trifluoromethyl, bicyclo[1.1.1]pentanyl, and cyclopropyl-trifluoromethyl substituents.

Pharmacological modulation of cannabinoid type 2 receptor (CB2R) holds promise for the treatment of numerous conditions, including inflammatory diseases, autoimmune disorders, pain, and cancer. Despite the significance of this receptor, researchers lack reliable tools to address questions concerning the expression and complex mechanism of CB2R signaling, especially in cell-type and tissue-dependent context. Herein, we report for the first time a versatile ligand platform for the modular design of a collection of highly specific CB2R fluorescent probes, used successfully across applications, species and cell types. These include flow cytometry of endogenously expressing cells, real-time confocal microscopy of mouse splenocytes and human macrophages, as well as FRET-based kinetic and equilibrium binding assays. High CB2R specificity was demonstrated by competition experiments in living cells expressing CB2R at native levels. The probes were effectively applied to FACS analysis of microglial cells derived from a mouse model relevant to Alzheimer's disease and to the detection of CB2R in human breast cancer cells.

DNA-encoded libraries of small molecules are being explored extensively for the identification of binders in early drug-discovery efforts. Combinatorial syntheses of such libraries require water-and DNA-compatible reactions, and the paucity of these reactions currently limit the chemical features of resulting barcoded products. The present work introduces strain-promoted cycloadditions of cyclic allenes under mild conditions to DNA-encoded library synthesis. Owing to distinct cycloaddition modes of these reactive intermediates with activated olefins, 1,3-dipoles and dienes, the process generates diverse molecular architectures from a single precursor. The resulting DNA-barcoded compounds exhibit unprecedented ring and topographic features-related to elements found to be powerful in phenotypic screening. File list (2) download file view on ChemRxiv strained_allenes-preprint.pdf (184.62 KiB) download file view on ChemRxiv strained_allenes-SI.pdf (2.14 MiB)

The endocannabinoid (eCB) system is implied in various human diseases ranging from central nervous system to autoimmune disorders. Cannabinoid receptor 2 (CB2R) is an integral component of the eCB system. Yet, the downstream effects elicited by this G protein‐coupled receptor upon binding of endogenous or synthetic ligands are insufficiently understood—likely due to the limited arsenal of reliable biological and chemical tools. Herein, we report the design and synthesis of CB2R‐selective cannabinoids along with their in vitro pharmacological characterization (binding and functional studies). They combine structural features of HU‐308 and AM841 to give chimeric ligands that emerge as potent CB2R agonists with high selectivity over the closely related cannabinoid receptor 1 (CB1R). The synthesis work includes convenient preparation of substituted resorcinols often found in cannabinoids. The utility of the synthetic cannabinoids in this study is showcased by preparation of the most selective high‐affinity fluorescent probe for CB2R to date.

Despite its essential role in the (patho)physiology of several diseases, CB2R tissue expression profiles and signaling mechanisms are not yet fully understood. We report the development of a highly potent,...

Molecular glues and bifunctional compounds that induce protein-protein associations provide a powerful and general mechanism to modulate cell circuitry. We sought to develop a platform for the direct discovery of compounds able to induce association of any two pre-selected proteins, using the first bromodomain of BRD4 and the VHL-elongin C-elongin B (VCB) complex as a test system. Leveraging the screening power of DNA-encoded libraries (DELs), we synthesized ~one million DNA-encoded compounds that possess a VHL-targeting fragment, a variety of connectors, and a diversity element generated by split-and-pool combinatorial chemistry. By screening our DEL against BRD4 in the presence and absence of VCB, we could identify VHL-bound molecules that simultaneously bind BRD4. For highly barcode-enriched library members, ternary complex formation leading to BRD4 degradation was confirmed in cells. Furthermore, a ternary complex crystal structure was obtained for the most enriched library member. Our work provides a foundation for adapting DEL screening to the discovery of proximity-inducing small molecules.